JWST's Iconic Primary Mirror. Credit: NASA Goddard Space Flight Center, CC BY 2.0 Three days ago on Monday 24th January 2022 at 19:00GMT, the James Webb Space Telescope (JWST) arrived at L2: the location where observations of Outer Space will take place. This means we've got a whole six months to wait until everything's calibrated and ready to take the first images (aka JWST's first light). So, what is there to do until then (well, apart from work, exams and other life events)? Here is a list of resources/activities for you to peruse/complete at your leisure so you can be fully briefed and ready for the day (some time in July/August): An event organised by ESA on YouTube/Facebook to teach you more about JWST (happens on Thursday 3rd February at 2-3pm (GMT)) though questions to be answered live are needed by 31st January at 4pm A NASA Eyes visualisation of where JWST is A webb page (see what I did there!) explaining what's happening with the JWST at the moment A list of deployments of JWST with videos and photos related to the events (you can scroll through the list on a bar at the top) An article I wrote explaining the ins and outs of the JWST (with lots of other useful links at the end for you to investigate) Take a photo of some artwork you have created which is what you believe images from JWST will look like (deadline is when the first images from JWST come in) and post them on Facebook, Twitter or Instagram with the hashtag 'UnfoldTheUniverse' View Webb's factsheet to get a brief overview of what the mission is all about Make an origami version of JWST's iconic mirror Create a bookmark representing the lifecycle of a massive star: something Webb will observe once it's up and running Play a quiz by NASA teaching you all about the different types of telescope and what makes each so unique If you find any other fantastic resources that you think would also sit well on this list, then please share them with me so I can publish them on this page! Use the email address: "webmaster.adas@gmail.com". by George Abraham, ADAS member #JWST #NASA #ESA #CSA #L2

At the Dawn of Time… plus a few hundred million years The James Webb Space Telescope (JWST) is an Infra Red (IR) telescope as tall as a three story house, as long as a tennis court, weighing the same as a school bus (6200kg) and designed, built and tested over 32 years using 40 million hours to built it with people from 14 different countries who are part of 3 space agencies (NASA, ESA, and the Canadian Space Agency, CSA). You may think it’s ‘just another Hubble’, but, whilst the images produced will be equally as stunning, the wavelengths (or colours) of light observed overlap a bit, and they’re both in space, that’s about all they’ve got in common. The James Webb Space Telescope partly folded up. Credit: NASA/Chris Gunn Let’s Start at the Beginning Thought of in a 1989 conference called “Next Generation Space Telescope Workshop” at the Space Telescope Science Institute (STScI) in the USA (with the JWST formally called the “Next Generation Space Telescope or NGST), scientists formally proposed it in 1996. They said it would be an Infra Red Telescope, using redder light than you can see (right so far) with a mirror larger than 4m in diameter (only 2.5 metres out!) with a budget of $500 million (Ah, just a mere $9.16bn out!). 2002 brought the selection of people to make it a reality, and 2004 marked the start of building work. By 2005, ESA’s spaceport in the French territory of French Guiana in north east South America was picked as the launch site. Being free from cyclones and earthquakes, and near the equator to give the reliable Ariane 5 rocket a boost in speed as it leaves the Earth due to Earth’s centripetal force, this was the perfect launch site. Indeed, everything was going so well… until they had to redesign it in 2005 to pick only the worthiest of instruments to be on board. This led to the original 2007 launch date being pushed back. An early concept of the JWST, called the Next Generation Space Telescope or NGST. Credit: NASA A True Multitasker JWST was given a lot of goals to achieve in its mission, selected over the many years of building, as science has progressed and many new questions have come to light. First off, the early Universe. It will look over 13.5 billion years into the past by looking at distant light and, due to light’s fixed speed, old light. Old enough to reveal the first stars (formed through cooling of molecular hydrogen) and galaxies which formed 300 million years after the Universe’s start in the Big Bang. The light emitted was at such high energy (Ultra Violet or UV, bluer in colour, outside of what we can see) that it’s detectable today as IR radiation, due to redshift (the elongation of light due to spacetime, the fabric of the Universe, is growing in all directions, meaning everything is moving away from everything else). This period of star and galaxy formation is called reionisation, where the first hydrogen atoms clumped to make the first and ‘purest’ stars, called ‘Population III Stars’. Artist's concept of the first population III stars Credit: NASA/WMAP Science Team Then, JWST can look over a galaxy’s lifetime to see how they evolve and how chemical elements distribute themselves in galaxies, before seeing what happens when they combine, like what will happen with the Milky Way and the Andromeda Galaxy in 3 billion years time. In terms of stars, JWST can look at how and where they first formed, helping to find what determines how many stars form in a location and their masses. Death also comes into play when JWST will observe how they ‘die’ (stopping fusing elements together) , how this ‘death’ impacts the surrounding environment. The black holes that stem from massive stars (over 10 times our Sun’s mass) will then be studied to find out, once and for all, what came first: the black hole in the centre of a galaxy or the galaxy itself. Another tension it may solve is that of the Hubble Constant: a number showing how fast the Universe is expanding. For an unknown reason, using supernovae (the cataclysmic event occurring after a star’s collapse) gives a higher value than that of the Cosmic Microwave Background Radiation (the CMBR: the remnants of the Universe’s earliest light which remains observable). The Cosmic Microwave Background Radiation (CMBR) Credit: NASA/WMAP Science Team Then there’s planetary systems, specifically looking at both exoplanets (planets outside our Solar System) and how they evolve, as well as if they’re habitable; and our Solar System. Notably, the JWST will observe superior planets (planets outside the area of Earth’s orbit) since JWST won’t need to look at the Sun (a source of IR light). For instance, scientists will use JWST’s IR vision to pier beneath the clouds of Jupiter, Uranus and Neptune to see what’s hidden (since IR light can penetrate clouds, also helpful when looking at early stars and planets, shrouded in gas and dust). As well as this, other mysterious objects will be imaged. Comets (balls of ice and dust) will have their spectra taken, showing what elements they hold from light they emit, and moons such as Jupiter’s Europa and Saturn’s Enceladus, improving our understanding of their potential habitability. False colour Cassini image of jets in the southern hemisphere of Enceladus. Credit: NASA If you thought that wasn’t enough, JWST has many more thousands of objectives, plus that of searching for the unexpected. Within 48 hours, JWST can stop a planned observation and whisk round to observe transient events like supernovae to improve our understand of them. Mister Gold… Mirror 2011 marked the completion of JWST’s array of mirrors. The primary mirror is the one you’ve probably noticed on all images of JWST: 6.6m diameter, with a collecting area of 25.4 square metres, and made of eighteen 20kg hexagonal segments. As the largest mirror to be sent into space, its back plate is made of beryllium (a rare, very light and strong metal at number 4 on the Periodic Table). This large mirror, 6 time the size of Hubble’s, means for a high resolution leading to detailed images, though you should expect strange lines from stars instead of the normal points of light you’ve seen in Hubble’s images, due to the unusual shape of the mirror A graphite-epoxy composite structure covers the beryllium, before a layer of gold is placed on top. You may have noticed a theme in science… we love gold, but not just because it’s great on rings. The 700 atom thick gold layer reflects IR light better than the normal silver-coloured coating used for space telescopes. JWST holds 3 other mirrors. The secondary is on the end of 3 arms and is a convex (bulging) circular mirror, only 0.74m in diameter. The tertiary mirror is within the telescope, almost rectangular in shape, at 0.73x0.52m. Then there’s the Fine Steering Mirror (FSM), which is the same shape as the primary, only much smaller! It is also within the telescope, there to stabilise the image with milli-arcsecond precision (where 1 arcsecond is a 60th of a degree). JWST's mirrors each individually photographed. "SM" stands for "Secondary Mirror". Credit: NASA Please DON’T Shine Bright Like a Diamond! From 2013-14 the mirror came together at NASA’s Goddard Space Flight Centre north of Washington DC. Then in 2013, work on the sunshield began. As long as a tennis court (21.2m by 14.2m) and made of five 0.025-0.05m thick membranes, this shield puts JWST in a 24 hour night. It reduces the light from the Sun from 200KW to less than a Watt, leading to a -233ºC telescope and a 110ºC outer shield: equivalent to a sun cream of SPF 1 million! This means there’s no interference of IR light from the Sun, as well from Earth and the Moon (IR light being responsible for most transfers of thermal energy, or heat, around an environment). Its extremely thin thickness means ripstops are built into all the sunshields to minimise the impact of micrometeorites and debris, so it doesn’t rip. JWST's Sunshield. Credit: NASA/Chris Gunn A Telescope with Many Eyes During 2013-16, all the scientific instruments onboard were subjected to vibration tests so we were sure they wouldn’t break on the way up to their destination in space. The ‘black box’ on JWST’s back houses the Integrated Science Instrument Module (ISIM) containing all these important instruments which will take light focused by the telescope and analyse it. The Near-InfraRed Camera (NIRCam) is a NASA instrument designed with a coronographic imager (a camera with something to block a source of light from shrouding out objects around it) and a wide field slitless spectrograph using grisms: a prism and a diffraction grating which spreads light into a spectrum, used so the camera can be used for spectroscopy and imaging. NASA hopes to observe distant transiting exoplanets, along with the first galaxies and their formation. Y dwarfs (cool stars in the Y part of the OBAFGKMLTY stellar classification), which contain methane, carbon dioxide, water and ammonia (organic, life giving compounds) and exoplanets will also be observed for signs of life and understanding what makes somewhere habitable. NIRCam in 2013. Credit: NASA/Goddard Space Flight Centre The Near-InfarRed Spectrograph (NIRSpec) is slightly different. A joint ESA NASA venture, it has a spectrograph with over a quarter of a million individually addressable shutters thinner than a human hair, to observe the spectra of around 100 sources simultaneously. This gives it a large 9 square arcminute (0.15 square degree) Field of View (FOV) to see transiting exoplanets and protoplanets (planets which haven’t yet developed), taking their temperature, mass and chemical compositions using their spectra. NIRSpec. Credit: Astrium GmbH, CC BY-SA 3.0 CSA’s (Canada’s) contribution to JWST is the Near-Infrared Slitless Spectrograph (NIRISS): the only instrument to contain an aperture mask (an opaque circle improving the contrast of bright objects by dimming them), used to investigate molecules present in the atmospheres of exoplanets, and find their temperature, mass and chemical composition, all using the transit method (where an exoplanet goes in front of its parent star, blocking some light) and spectroscopy to investigate them. NIRISS. Credit: NASA The Mid Infra-Red Instrument (MIRI) is another ESA and NASA partnership, headed partly by the UK Astronomy Technology Centre in Edinburgh. Its use of a redder part of the IR spectrum means it can look at star formation, since many molecules have fundamental bands in the mid IR spectrum (being bands which scientists can use to say a molecule is present). It can also look the furthest back in time at galaxies with the highest redshifts (along with colder, and so redder, but closer objects). As well as the spectrograph, it has an integrated field unit, with a camera and spectrograph, capturing and mapping spectra across its field of view. Its Mid-IR imager means it also must be cooled to 33ºC less than everything else (reducing interference from cooler Mid-IR light from the Sun), cooling it to just 7ºC warmer than Absolute Zero: the temperature where molecules stand still. However, this and the technology behind the imager mean it’s 50 times more sensitive than Spitzer: one of the largest IR telescope in space. MIRI. Credit: NASA All Systems Go! Now… no! Now!… I mean, erm… now!! In 2017 vibration and temperature tests were underway, ensuring nothing would stop working due to the vibration from the rocket on lift off and the dramatic changes in temperature from Earth to near Absolute Zero in space. Then, in 2018, during the assembly and testing phase, the sunshield tore! Yes, the one with all the protections to stop this from happening tor. So, it took another 2 years and another push back of the launch date to get it ready for launch. All eyes looked to 2020, but Covid-19 happened and it had to be pushed back to make way for missions like NASA’s Perseverance Rover, which had a specific time window for launch (unlike JWST). 2021 came and, in August, the Ariane 5 rocket to take it to space was grounded due to an issue with the payload fairings (what stores the observatory when getting it to space). Then, in late November, a clamp band (something on the telescope, a bit like an elastic band) released, shaking the telescope, leading to a further delay to wait for it to stop shaking. Then came December, where unfavourable winds led to the date being moved again to Christmas Day, when we currently expect lift off to occur. And LAUNCH! On Christmas Day at 12:20pm, I’ve got just the thing to have on in the background during Christmas lunch! Any time after 12:20pm, Ariane 5 will lift off from French Guiana, taking with it JWST. 2 minutes later, its boosters (the towers attached either side) will separate, before the fairing (containing JWST) splits in two a minute later. Just 9 minutes after launch, JWST will be freed from the main stage and flown for 18 minutes by a spacecraft below, before that too leaves. Since JWST is battery powered, the first thing to deploy will be its solar panel, just 2 minutes later, before the high gain antenna deploys 2 hours after launch to make contact with Earth. Ariane 5 on the launch pad with JWST in it. Credit: ESA - S. Corvaja 12 hours after launch, JWST will fire up to make its 29 day journey to the Sun-Earth Lagrangian Point 2 Halo Orbit (L2 for short). This is a point where Earth and the Sun are always directly in front, and where the gravitational pull from both equals the centripetal (turning) force from JWST, decreasing the fuel needed to stay there. At 1.5 million km away from Earth, it’s 4 times further away than the Moon. Whilst it’s on the voyage, JWST will unfurl its sunshield, before opening out its primary and secondary mirrors, like, as NASA’s Keith Parish put it, a transformer, to become a star destroyer (from Star Wars) with a ray gun on top (accurately put!). That said, there are 344 things that can go wrong, 80% of which are in the deployment, so this is arguably the most tense part. 2 to 6 months after launch, JWST will be calibrated and cooled to its chilly -233ºC, making it ready to take its first images. JWST's Sunshield opening. Credit: NASA/GIPHY Let the Science Begin! 6 reaction wheels which store angular momentum, 6 gyroscopes and 3 star trackers help position JWST within arcseconds of its target, pointing at 60% of the sky at any one time, pointing at any one point for anywhere from a few minutes to 14 days. The science for JWST’s first year (known as ‘Cycle 1’) has already been planned, with the General Observers Programme including 2,200 investigators from 41 different countries using 6,000 hours of time. There’s also the Director’s Discretionary Early Release Science, taking place in the first few months of JWST’s life, with 13 programmes in place to demonstrate Webbs capabilities to the world. Then, for anyone luck enough to be affiliated with JWST, there are the Guaranteed Time Observations, where people have been allocated time on it for working on creating the telescope. The End… already? Hubble has, so far, worked for 32 years, providing amazing images that we’ve come to take for granted. However, JWST works a bit differently. When any telescope turns, the Sun exerts a pressure on it, making it tumble. To counteract this, Hubble used magnetic bars to connect to Earth’s magnetic field to counteract this (needing no limited fuel supplies). However, being 1.5 million km from Earth instead of just 570km, JWST can’t do this, so it uses propellent instead. And there’s only enough for 10 years of operations, so there’s no way we’re going to get any extra years out of JWST (since it can’t be refuelled). Eventually, JWST will drift out of orbit in L2 and become dysfunctional, since it won’t keep a steady view of objects. The next 10 years of science from JWST will certainly be exciting, especially for the first image which will be produced in, hopefully, 6 months time. However, even after its time is up, as with many missions from Apollo to Hubble, the scientific papers will keep coming for years to come as more and more people look at data produced from this ground breaking telescope. Webb being packed up before its launch on Christmas Day (hopefully!!). Credit: NASA/Chris Gunn by George Abraham, ADAS member. #JWST #NASA #ESA #CSA #Sunshield #Telescope #Exoplanet #Saturn #Jupiter #Europa #Enceladus #Comet #CMBR #Redshift #InfraRed Click here for the previous news article Click here for the next news article Click here to make your own JWST Click here to see the place where all data from, not just JWST, but TESS and Hubble, store there data, and have a brows through images Click here to participate on the launch online with NASA Click here for the live stream from NASA of the event Click here for the live stream from ESA of the event Click here to explore all science questions the JWST hopes to answer Click here for the countdown to the launch Click here to track JWST on its journey after launch Click here to see where the organisations who took part in making JWST are based References "Webb". ESA. Archived from the original on 24th December 2021. "Small Steps, Giant Leaps: Episode 73, James Webb Space Telescope". 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History of Communication Satellites in a Nutshell These days we can call up someone in the remotest parts of Antartica and have a conversation as though they were right next to us. However, without the nifty technology that is the ‘Satellite’, none of this would be possible. They were first mentioned by Arthur C. Clarke (author of ‘2001: A Space Odyssey’) in his article ‘Wireless World’ written in 1945, where he described the transmission of TV programmes from manned satellites in 24-hour orbit around Earth; and then later looked at in detail by John R. Pierce in 1951-2, paving the way to the first communication satellite to be launched in 1957: Sputnik 1. Sputnik 1 Replica. Credit: NSSDC, NASA Following this, many more innovations came and with this, many more communication satellites. From Telstar 1 in 1962 which transmitted the first satellite TV (including images of the Eiffel Tower and Statue of Liberty, since it was sent from Brittany to Maine in north east USA); to e-BIRD: a broadband satellite which provided signal to parts of Europe with none. As well as their many innovations of everything from what they could transmit to where in Earth’s orbit they were (more on that later), communication satellites have also famously been getting smaller; a lot smaller. The small light (from 1 to 10kg) nanosats have become very popular in recent years: ever since the first six in June 2003, they’ve been providing an affordable way to collect data and send it back to Earth, needing little fuel to send them into Space and little material to make them. Another miniaturising innovation is the the smallsat: a satellite class slightly bigger than the nanosat at less than 180kg. They have been especially popular as communication satellites; most notably with Starlink and OneWeb. Aside from the disruption of Earth-based astronomy, their focus is on fast global broadband, reaching places that couldn’t get an internet connection before using much cheaper methods than older broadband satellites to provide more universal coverage [1][2][3][4][5][6][7]. Model of OneWeb Satellite. Credit: NASA/Kim Shiflett Where are they? The simple answer is, of course, in orbit around Earth. However, Earth’s orbit is a very big place, so there are various common orbit types: Geostationary Orbit (GEO), Low Earth Orbit (LEO), Medium Earth Orbit (MEO), Polar Orbit and Sun-Synchronous Orbit (SSO), Transfer Orbits and Geostationary Transfer Orbits (GTO) and the Lagrange Points (L-points) [8]. First, let’s look at GEO: 35,786km above Earth and travelling west to east to follow the rotation of the Earth along the equator, thereby staying above the same place on Earth at all times. They can serve large sections of Earth with constant coverage, and so ensure that area always gets coverage (for relaying signals, for instance) or is continually monitored (like with weather satellites) [8]. LEO is, as the name suggests, low: less than 1000km high to be specific, following any plane (angle of orbit) they want, meaning there’s lots more space for satellites. This makes them fantastic for imagery satellites, but not so for satellite communications, since they’re travelling so fast, orbiting 16 times a day. However, mega-constellations like those of Starlink and OneWeb are in LEO, so how? It’s down to the fact they work together to cover the whole Earth at once, seamlessly changing the satellite in use after the previous one used is out of range. All this makes it extremely popular, whilst also creating a mine field of space debris [8][9]. And where does our prized GPS fit into all this? Well, GPS satellites (along with other navigation satellites such as ESA’s Galileo system) orbit in MEO, found between LEO and GEO. They have the advantages of a lower time to send signals than in GEO, a larger footprint across Earth than LEO, and the option of going in any plane around Earth [8][10]. Like LEO, SSO orbits at a similar altitude (600-800km) and does what it says on the tin: it orbits so, relative to the Sun, it’s fixed in the same position all the time, flying over certain locations at the same time each day and going over the North and South Poles within 20-30 degrees. This is helpful in seeing changes over time at certain places [8]. Scale diagram of where the orbits around Earth are. Credit: Rrakanishu, CC BY-SA 4.0 Want to use little fuel but still want to go all the way to GEO? Simple; use GTO: putting a satellite into a GTO when offloaded will let them move, with little use of the satellite’s energy, into a higher orbit. This is because it’s an elliptical instead of circular orbit, with two foci instead of one (points where a curve is constructed) — in other words, a stretched circular orbit [8]. However, what if you want to go much much further out? This is where the Lagrange Points come in. Totalling five, they are the points far away (1.5 million km) from Earth where a satellite can have a stable orbit, found using some cool maths curtesy of one Joseph-Louis Lagrange [8][11]. Where the Lagrange Points are relative to the Earth and the Sun. Credit: NASA/WMAP Science Team How to Navigate and Phone from Space What do we do if we don’t have this massive network of satellites though, like when you’re a spacecraft flung off into the far reaches of Space? That’s where NASA’s Deep Space Network (DSN) and ESA’s Deep Space Antennae (DSA) come in. They are groups of enormous radio antennae (everywhere from Madrid in Spain, to just north of Perth in Australia) which transmit and receive data, used for telemetry (receiving the scientific data spacecraft collect) and command (controlling what the spacecraft does) [12][13]. However, as well as this, they also help with the problem of navigation in Space. The antennae send signals to the spacecraft and time how long it takes to arrive at a receiving dish after a signal has been transmitted by the spacecraft, determining: how fast the craft is travelling, its distance from Earth, and where the spacecraft is in the sky. A signal can then be transmitted to instruct the spacecraft as to how it can change its course [13][14][15]. A 70m antenna in Robledo de Chavela near Madrid, Spain, used in NASA's DSN Credit: Hector Blanco de Frutos, CC BY 2.5 That said, on longer missions, it may take many minutes, hours or days to do this (around 2.7 days for the Voyager 1 probe to receive, send and then receive a signal [16]). This is where pulsars come in: neutron stars (dying massive stars) which send regular pulses of light from their poles as they rotate. The spacecraft can use three sources of these pulses (the quicker the more precise) to measure changes in the timing between each pulse, thereby pinpointing its location in space [15]. Navigation and Communication on the Moon Unlike the far reaches of Space, the Moon is much much closer. This means that some Earth based technology already in place can be used: notably our global navigation systems, such as GPS. Their signals may be directed towards Earth, but some signal spills over into Outer Space. And some engineers think we could use that ‘spill-over signal’ to navigate, though the signal would be pretty weak [15]. This is where a new generation of satellites come into play: ones which take out the time issues; the weakness of signals and the trouble with a body like the Moon coming between you and the Earth. It’s called Lunar Pathfinder [17]. With the help of Surrey Satellite Technology Ltd (SSTL - announced on 16th September), a satellite manufacturer based just outside Guildford in central Surrey, ESA will put a single satellite into orbit around the Moon in 2024 to provide continuous communication services for both robots and humans on the lunar poles and its far side (the side which never faces Earth) because there are thought to be sources of oxygen, rocket fuel and water in those locations [17][18]. It will also hold three experiments: an ESA receiver to detect the signals from GPS and Galileo (ESA’s version of GPS) from Earth, demonstrating the possibility of Lunar navigation with the aid of Earth and Moon based satellites; a NASA mirror (or retro-reflector) to demonstrate the possibility of laser ranging (tracking the positions of the satellites by measuring the laser light reflect off them [19]); and an ESA radiation detector to measure levels of radiation in orbit [18]. To do all this, the Lunar Pathfinder satellite will be put into a lunar orbit called an ‘Elliptical Lunar Frozen Orbit (ELFO). The ‘frozen orbits’ are where spacecraft can orbit the Moon at a low altitude (800-8,800km) indefinitely (though this satellite will end its mission after 8 years), and at a range of inclinations (angles of orbit): 27º, 50º, 76º and 86º (very close to those all important Lunar polar regions) [20][21]. Image showing the various missions which are part of the future lunar initiatives including NASA's Artemis programme and ESA's Moonlight programme. Credit: ESA In years to come, we may have an array of satellites helping our astronauts and robots on the Moon find where they are and communicate with the same ease we enjoy on Earth. by George Abraham, ADAS member. #Moon #Satellite #ESA #SSTL #NASA #GPS Click here for the previous news article Click here for the next news article Click here to look at the current state of NASA's Deep Space Network (DSN) Click here to see where ESA's Deep Space Antennae are located Click here to look at how ESA's Ground Stations are doing (which include ESA's Deep Space Antennae) - found at the bottom of the page References "Communications Satellites: Making the Global Village Possible". NASA. Archived from the original on 18th September 2021. "A Brief History of Satellite Communications". Ground Control. Archived from the original on 18th September 2021. 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Photo of the Chair with Audrey Binch, Alma Singers Chair and Andrew Jeffries, Sale Male Voice secretary Credit: Christine Lavender I am extremely pleased to report that the Timperley Country Fair on Saturday was a success well beyond reasonable expectation and, particularly, for the joint ADAS and Trafford Arts Association stall. The attendance at the stall by all age groups was outstanding. The children’s quiz, galactic star search and alien drawing were enthusiastically tackled by many very young to youthful participants. Copies of the quiz and star search were taken to be completed at home, scanned and emailed back to the chairman. The outdated leaflets handed out to the public were verbally amended re: the website address and email contact and recipients were referred to the internet to access 'astroadas.space' for current info. Several local people were potential recruits for membership to ADAS. Also the TAA display was well-received. The chair arrived at 8.00 and was assisted by Parkinson’s Trafford branch in erection of the TAA gazebo. The stall was set up before members of the TAA arrived at 10.00 am and others, later on. Chris Lavender, ADAS, was in attendance for the majority of the day. Interviews were arranged by ALTY local radio at which both the Chair for ADAS and Andrew Jeffries for the TAA promoted the organisations in some detail. Heartfelt and grateful go to Christine L (ADAS), Andrew Jeffries, Bob Davies (both of Sale Male Voice), Audrey Binch, Terry Oddy (both of Alma Singers) for their enthusiastic attendance. The fair closed after 4.00 pm and the chair was assisted by TAA members, Andrew and Terry, in deinstallation of the displays and gazebo. A report will verbally presented at the next ADAS meeting. Apologies were noted from Ged and several TAA members. Take care and stay safe. by Peter Baugh, ADAS Chairman. #TimperleyFair Click here for the Timperley Country Fair website

The Bone The bone in question is one “216 Kleopatra (A880 GB)” named colloquially as the “Dog Bone” because of its bone-like appearance. It is an asteroid (otherwise known as a minor planet) lying over 200 million kilometres from Earth in the Asteroid Belt, and measures only 270 kilometres in diameter [1][2][3][20]. However, how did such an asteroid come to be? It all comes down to the formation of our Solar System some 4.6 billion years ago (for comparison, the Universe is only 3 times older than that!). This asteroid, along with others (1,113,527 in all currently) ranging from just 10 meters to 530 kilometres across (Vesta), started their lives in the proto-planetary disk of gas and dust orbiting the young Sun. The planets coalesced themselves from this soup, along with many smaller objects such as dwarf planets (like Pluto — sorry!), during the first 5 million years of the Solar System [3][4]. They formed into larger and larger clumps due to the effects of gravity, whilst other material wasn’t so lucky, forming into small clumps and scattering into the Asteroid Belt and Kuiper Belt (due to the positioning and orbits of the planets) [4][5]. Kleopatra seen at different angles on different dates Credit: ESO/Vernazza, Marchis et al./MISTRAL algorithm (ONERA/CNRS), CC BY 4.0 Asteroid Composition To differentiate them from comets (bodies with two bright tails), asteroids are defined as rocky bodies, as opposed to the comet’s icy composition. There are three classes: C-types, S-types, and M-types. C-types (or Carbon-types), also known as chondrites, are the darkest colour, most common and oldest types of asteroid. Named because of their high carbon content (making them look charcoal-like), they’re made of clay and silicate rocks. Their age is testament to their distance from the Sun (in the outer reaches of the asteroid belt mainly), leading to them only heating up to below 50ºC [6]. You may have heard about the famous Winchcombe meteorite being called a carboniferous chondrite (or CM2-type). It’s similar to the pure chondrites I’m talking about, though these are also similar in composition to the Sun (without the volatiles like hydrogen and helium), providing an unprecedented view into the Solar System’s history (considered to be the best preserved bodies from the very beginnings of the Solar System) [7]. The display of the Winchcombe Meteorite in the Natural History Museum Credit: Amanda Slater, CC BY-SA 2.0 Then there are the the S-types (or Siliceous-types), which are the 2nd most common in the Solar System. They make up some of the largest known asteroids (some big enough to be seen through 10x50 binoculars) and are found a bit further in than C-types, in the inner asteroid belt. They’re made of mostly nickel-iron and magnesium silicate materials, leading to a brighter appearance than their C-type counterparts [8]. 253 Mathilde. Credit: NASA And finally there are the the M-types (or Metallic-types), which are some of the least studied asteroids, with only part of their composition known to us, though what we do know is many are made of nickel-iron sometimes mixed with stone. They’re found in the middle of the asteroid belt and can get up to 200km in diameter. This is in fact the type our Dog Bone is, metallic in composition (though predicted to be 50% empty space to make its density the low 3.6 grams per cubic metre it is) [9][10]. The Widmanstätten pattern seen within many M-type meteorites. Credit: Daniel Baise, CC BY-SA 3.0 You may wonder how they can classify asteroids into such ambiguous categories, but there is in fact an easy way, through spectroscopy. More specifically, it’s through looking at the spectra of light reflected off the asteroid, as well as light produced by the asteroid (heat being given off as low-energy light). The shape of a spectrum (usually on a graph of the strength of light, or the amount reflected, against the wavelength or energy of that light) then dictates what elements are present in the asteroid, and therefore what category it fits into [11]. Graph showing the spectrum of an asteroid which orbits a different star: white dwarf GD 40. This shows that this particular asteroid is high in silicates. Credit: NASA/JPL-Caltech/UCLA The Dog To find our bone scientists employed something which is used a lot on anything from ships to military bases to some cars: radar. Standing for “RAdio Detection And Ranging”, a radar instrument sends a pulse of microwaves (low energy light, like what you find in your microwave, but much stronger - though they won’t cook anything in their way!) to the object in question, before an instrument measures the signal which is reflected (otherwise known as an echo). The Arecibo Observatory (was used partly to observe planets using radar technology). Credit: JidoBG, CC BY-SA 4.0 Because scientists know the properties of the signal which was sent, they can deduce what the properties of the object are by using the idea of doppler shift (when the wavelength of the light is either stretched or squashed, making the light redder or bluer) by comparing the received signal to the transmitted signal. Unlike other astronomical observing methods, radar actively creates a signal, meaning measurements can be more precise. In fact, it’s so useful it has been used to accurately map Mercury, the Moon, Mars and Venus, as well as many asteroids including our Dog Bone. In fact, on 14th August 2021, the 1,000th asteroid (2021 PJ1) was observed using radar, just over 50 years after it was first employed for this use to observe the first target: 1566 Icarus. The North Pole of Venus as seen by the Magellan probe which used a radar to penetrate Venus' clouds and observe Venus. Credit: SSV, MIPL, Magellan Team, NASA However, it can’t be used for further away objects because of Inverse-Square Law: energy dissipates, spreading to 4 times the area when it’s twice as far from the source, leading to the intensity of light dropping to a quarter of the previous intensity. This means that the echos of signals can’t be observed if looking at far-off targets without pumping lots of energy into the signal [12][13][14][15][16][17][18]. Diagram to show inverse square law. Credit: NASA/JPL-Caltech Kleopatra’s Friends The asteroid observed isn’t your normal target by any stretch, not only because of its ‘bone-like’ appearance, but because of the two moons that orbit it. Named AlexHelios and CleoSelene (after Cleopatra’s twins: Alexander Helios and Cleopatra Selene II), the moons (or more correctly, the satellites - moons are only classed as bodies in orbit around the planets [19]) are explained by Kleopatra’s formation as a rubble pile held together by gravity: the collision of two asteroids to form one. Any time after the start of the Solar System the asteroid came to be after a collision with another asteroid. Then, 100 millions years ago, the asteroid was impacted by another asteroid, causing it to spin much faster than it was previously. This caused it to elongate and eject what came to be the most distant of the two moons: AlexHelios. Then, around 10 million years ago, the inner CleoSelene was shed. These moons aren’t just there for show though: they’ve helped scientists determine Kleopatra’s density by looking at their orbits [20][21]. Image taken by the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument on the VLT, showing the two moons and Kleopatra. Credit: ESO/Vernazza, Marchis et al./MISTRAL algorithm (ONERA/CNRS), CC BY 4.0 Observing The Dog Bone Recently, the European Southern Observatory’s (ESO) Very Large Telescope (VLT) observed the Dog Bone, obtaining the best images yet of it, creating a 3D model of its unusual shape. Not only does it show the Dog Bone itself, but also the two moons that orbit it, helping them calculate new and more precise estimates for Kleopatra’s mass and volume. It was 35% lower than previously thought, showing Kleopatra must be extremely porous and backs up the rubble theory. It was also found to be 270km in length, similar to that of the English Channel! Also, they found its rotation was almost at critical speed: the speed at which the asteroid would fall apart. This then backs up the other theory that the asteroid shed the two moons it has today. SPHERE Optical Bench (an instrument on the VLT to improve the detail and accuracy of images taken by the VLT, such as the one of Kleopatra). Credit: ESO, CC BY 4.0 However, with the new telescope being built by ESO (the Extremely Large Telescope, or ELT) it’s hoped that even better measurements can be taken of 216 Kleopatra, along with the possible discovery of smaller satellites that orbit this strangest of asteroids [20]. by George Abraham, ADAS member. #Asteroid #Kleopatra #ESO #radar #VLT Click here for the previous news article Click here for the next news article Click here to see the list of asteroids observed by using radar Click here to look at where a visible C-type asteroid is in the sky (10 Hygiea, from an apparent magnitude of around 9 to 11) Click here to look at where a visible S-type asteroid is in the sky (3 Juno, from an apparent magnitude of around 7 to 11) Click here to look at where a visible M-type asteroid is in the sky (16 Psyche, from an apparent magnitude of around 9 to 12) Click here to look at the news article about the Winchcombe meteorite by the Natural History Museum, who now has the meteorite on display. 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The Cloud Stars all come from interstellar gas and dust: a perfect concoction of different elements and molecules made as a result of the death of a star. This is made in events such as planetary nebulae: clouds of dust and gas spewing in a circular pattern away from a white eye in the middle (the white dwarf) as a result of the outer layers of a red giant ripping apart because it has become highly unstable in its old age [1]. Events like these, along with other events such as supernovae (explosions at the end of lives of massive stars, greater than 10 times the mass of our Sun) then led to all the dust and gas that’s floating about in the Universe today, visible as clouds which either emit or absorb light, producing characteristic dark holes and glowing regions in the sky [2]. Evidence of this lies in the star that results from these clouds, emitting specific wavelengths of light, revealing what elements lie within: elements only obtainable due to what goes on at the end of a star’s life, when it run out of hydrogen and helium fuel to fuse to carry on churning out the immense amounts of energy it emit throughout its lives [3][15]. Collapse However, to get the cloud into the concentrated form needed for a star, the clouds then need to coalesce. The process starts by a trigger, leading to the cloud beginning to fragment. This trigger can be many things, including clouds colliding into each other (a possible explanation for spontaneous star formation within clouds found in Serpens: a constellation containing the Pillars of Creation, among others); or even the shockwaves from a supernova explosion. Indeed, this particular theory is thought to be a possible explanation for the Solar System’s birth, since short lived isotopes formed by Supernovae have been found to be trapped within meteorites formed at the start of the Solar System (also called ‘primitive meteorites’). Then, as the gas and dust in the cloud collapses, it heats up, radiating this heat into the surroundings to carry on collapsing and increasing the gravitational pull and pressure within the now dense gaseous area. However, as this area gets hotter and hotter because of the ever increasing pressure, the gas and dust stops collapsing since the immense thermal energy pushing out wins over the weaker gravitational energy pushing in: hydrostatic equilibrium [4][5][6][7][8][15]. The Pillars of Creation, with high levels of star formation visible as the glowing tips of the pillars Credit: ESO, CC BY 4.0 Protostar A star is then born, glinting out of the darkness (created due to the high density of surrounding material) like an eye lifting its lid on the world. However, the story is not over yet! This new star keeps on shrinking and shrinking like Alice in Wonderland, until its core reaches the key temperature of 10 million Kelvin (around 10 million ºC). However, whilst it’s shrinking, unlike Alice, it also has a spin [4]. And as the radius of the cloud shrinks, it begins to spin faster and faster due to the centripetal force (like when you feel a stronger pull the closer you are to the middle of the roundabout when it’s spinning), leading to a circumstellar accretion disc around the equator (a disc made up of the gas and dust from the cloud it came from), whilst the remaining matter is sucked into the star to be ejected at a later date in jets created by a newly formed magnetic field (like the relativistic jets of black holes, only much weaker) [7][11]. Looking at the temperature now, it may seem a random number but it’s the temperature that coulombic repulsion (the force which repels two particles of the same charge) between hydrogen ions (protons) becomes less than the attraction between the ions, leading to hydrogen fusion to make helium and energy: the way most stars, such as our Sun, make energy. This temperature marks the second time where a star reaches hydrostatic equilibrium [9][10][4][15]. Jets streaming from a protostar HH 212 (Herbig-Haro object) Credit: ESO/M. McCaughrean, CC BY 4.0 Stellar Adolescence of Low-Mass Protostars If a protostar is 3 times the mass of our Sun or less and is still collapsing (since low-mass stars collapse much slower than high-mass stars), it’s known as a T Tauri star (TT for short). They eject material at up to 500,000 kilometres per hour, ejecting a mass equal to the Sun in its 10 million year lifetime. And this evolution through the emission of matter marks the transition from a baby protostar into a fully fledged star: a timescale also known as the Kelvin-Helmholz timescale. It is characterised by how the initial source of energy during this time is not nuclear fusion (since the high temperature seen in high-mass protostars hasn’t been achieved yet) but gravitational binding energy: the energy it takes to bind everything together into a body. The jets discussed earlier are also still present, leading to the star emitting variable energy, meaning that the star pulsates: a variable star (where the star visibly changes in brightness) [12][13][14][15]. Hubble images of binary system XZ Tauri, at a scale much larger than the Solar System (the two stars seen as circles in the bottom left are at a similar distance to Pluto and the Sun Credit: John Krist (STScI), Karl Stapelfeldt (NASA Jet Propulsion Laboratory), Jeff Hester (Arizona State University), Chris Burrows (ESA/STScI) Smaller Still Protostars can only become real stars if they have enough material though. Anything less than that and it’s a non-starter; a brown dwarf. At masses less than two twenty-fifths of the Sun’s mass (0.08 solar masses), the internal temperature of the star can never reach the heights of 10 million Kelvin due to the matter’s low gravitational attraction. This leads to an absence of nuclear fusion, though not the absence of any emission, with infra-red radiation (light at the low energy, redder, part of the spectrum) still being emitted. However, brown dwarfs are nothing to be laughed at, with enough energy to emit infra-red radiation for more than 15 million years (part of the Kelvin-Helmholz timescale), and they are a similar size to that of Jupiter (but much hotter). Plus, due to their low emission of radiation, and therefore their hidden nature in the night sky (being much harder to find than their bright stellar counterparts) they could be part of the missing mass that we’re looking for in the Universe, labeled mostly as ‘dark matter’, but could in fact partly consist of brown dwarfs [15][16]. Images of the Gliese 229 system, consisting of Gliese 229A (the big one) and Gliese 229B (the much smaller one, which is a brown dwarf, 20-50 times Jupiter's mass). Credit: T. Nakajima/S. Kulkarni (CalTech), S. Durrance/D. Golimowski (JHU), NASA Scanning the Skies To learn more about these relatively dark events, a team of researchers using MUSE (the Multi-Unit Spectroscopic Explorer) on the VLT (Very Large Telescope), along with ALMA (the Atacama Large Millimetre/sub-millimetre Array) both at ESO (the European Southern Observatory), have recently released images of galaxies. Known as PHANGS (Physics at High Angular Resolution in Nearby GalaxieS), the team has put together pictures, described by ESO as “galactic fireworks”, which will help shed new light on the triggers of star formation (with the current science described earlier). These images provide astronomers with detailed information about the gases that later lead to star formation, and helping them create an ‘atlas’ of stellar nurseries (interstellar gas and dust which lead to star formation) in the nearby Universe. These include around 100,000 cold-gas regions and 30,000 nebulae of warm gas [17][18][19]. Five of the galaxies observed by MUSE (which is on ESO's VLT), shown as stacks of observations at several wavelengths of light. The golden glows reveal clouds of ionised hydrogen, oxygen and sulphur gas which are home to stars just coming into existence. Find out more here. Credit: ESO/PHANGS, CC BY 4.0 Hopefully with this new data scientists will understand, in more detail, the formation of stars, possibly leading to a better understanding of exactly how our own Sun, along with the planets that surround it, came into being. by George Abraham, ADAS member. #Star #ESO #Protostar #Gas #Dust #TTauri #BrownDwarf #Supernova #Nebula Click here for the previous news article Click here for the next news article Click here to watch a computer simulation of stellar formation in MACS1149-JD1 (one of the furthest known galaxies from Earth) Click here to Watch a simulation of the collapse of a cloud and the formation of a brown dwarf Click here to watch the formation of a massive protostar Click here to watch ESO's video about the 'atlas' of stellar nurseries compiled by PHANGS Click here to look at the maths behind stellar formation References "Planetary Nebula". National Schools' Observatory. Archived from the original on 16th July 2021. 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Gravitational Waves The story starts with gravitational waves. The term ‘waves’ makes them sound deceptively simple: flick a light switch or play music through a speaker and almost instantaneously you can detect that light and sound are real things, through using your eyes and ears, and very little energy. Gravitational waves, on the other hand, need a lot more energy to create detectable waves, since gravity is such a weak ‘force’. Or, more accurately put, spacetime (the fabric of the Universe which depresses when an object is within it) is hard to deform. When there is enough mass and energy though, it can depress, sending out waves to communicate to other parts of the Universe the change in the distribution of mass and energy in that place (since nothing, not even simple information like mass and energy, can travel faster than the speed of light). And when an event such as a black hole collision or supernova occurs, the spacetime around the object begins to stretch and squash, like mesh being stretched in two directions (with spacetime being a 4 dimensional ‘material’, where there’s height, depth, length as well as an internal structure). If you’re confused, don’t worry! Click here and watch a short explanation by a scientist who has found a novel use of some mesh from a wine bottle [1]. Black hole merger producing gravitational waves. Credit: LIGO/T. Pyle Signatures in Waves The waves detected at gravitational-wave interferometers like LIGO (an ‘L’ shaped detector that looks for deformations in each arm that are the 1,000th the diameter of a proton [1]) lead to a graph of the frequency of the waves by time (much like the frequency of ripples moving past a point in a pond, but along two axes). The way in which the frequency of waves rises and falls helps scientists work out the mass and spin of the objects involved in making these waves by comparing them to simulations of events. LIGO Livingston, at the corner of the L Credit: Caltech/MIT/LIGO Lab One example of this is the very first time gravitational waves were detected, on 14th September 2015. The graph of the gravitational waves showed the three main stages expected from black hole mergers: inspiral, merger and ring-down. Inspiral is where the two black holes are orbiting one another, moving faster and faster as they get closer and closer (the frequency of gravitational waves increases). Then, the merger event happens, where the ISCO (Innermost Stable Circular Orbit: the part where nothing can stand still, but where you can still escape) of each black hole touches the other, leading to an ISCO plunge, before the black holes merge to form a Kerr black hole (one with no electric charge): the point where the waves have the highest frequency. Following this, ring-down happens, where the frequency quickly drops, like the ringing of a bell slowly fading away after being struck. The combination of these stages is known as a chirp, due to the characteristic sound made by converting the graph into something audible. With this general wave form in mind, just a few numbers for the spin and masses of the black holes are needed and a perfect wave form is obtained from a simulation, matching that measured by a detector. And, with every event, there’s a different signature for the different masses, spins and processes involved [2][3][4][5]. The first observation of gravitational waves by LIGO (with one detector in Hanford and another in Livingston) Credit: B. P. Abbott et al. (LIGO Scientific Collaboration and Virgo Collaboration), CC BY 3.0 Types of Events Gravitational waves are most famously formed by the collision of two black holes, as seen in the very first collision measured. These are known as Compact Binary Inspiral Gravitational Waves, formed by two neutron stars colliding (Binary Neutron Stars or BNS), two black holes colliding (Binary Black Hole or BBH) and a neutron star colliding with a black hole (Neutron Star-Black Hole Binary or NSBH) [6]. As the two objects get closer, their orbits accelerate due to a centripetal force (a force directed into the centre of motion, in this case due to the strong gravitational attraction between the two objects). This then leads to the inspiral, merger and ring-down that was explained earlier [7]. From the 14th September 2015 detection of gravitational waves from a black hole merger, 53 mergers have now been confirmed by the LIGO and Virgo detectors. This treasure trove of observations led to the first neutron star merger detection on 17th August 2017. It revealed the illusive kilonova: the rapid decay (through the r-process) of neutrons expelled by the neutron stars, creating a burst of energy, detected by LIGO and Virgo as a chirp [7][8]. However, the exciting thing about a neutron star merger is that it’s detectable using conventional telescopes, such as the Fermi gamma ray (high energy light) telescope, detecting a burst 1.7 seconds after the chirp detected by LIGO and Virgo. This then led to spectra being taken which showed that elements present in the burst included Lanthanides (heavy elements in the periodic table), hinting at neutron star collisions being responsible for elements such as gold and platinum [9]. First signal of a neutron star collision (GW170817) Credit: LIGO Scientific Collaboration and Virgo Collaboration, CC BY-SA 4.0 And then, on 5th January 2020 and 15th January 2020 (confirmed on 29th June in a paper), the LIGO and Virgo detectors picked up the signal of a neutron star and black hole colliding, an NSBH: a first for the detectors. The first collision (known as GW200105) expelled 0.34 to 0.41 quattuordecillion Joules of energy (up to 3.4 trillion times the energy output of the Sun in a year) whilst the second (known as GW200115) expelled slightly less, at 0.22-0.34 quattuordecillion Joules. However, this staggering amount of energy wasn’t able to be seen with telescopes like the neutron star mergers, possibly because the black hole gulped up the neutron star before it could through out a burst of light. That said, scientists aren’t totally sure, since the light may just not have been located due to the vastness of the sky is was predicted to have come from (17% of it), and the distance the light would have travelled to get here meaning it may be extremely dim (with the event happening up to 1.3 billion light-years away) [8][10][11][12][13]. Simulation of a black hole neutron star merger with a tidal disruption. Credit: Scientific visualization: T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics), N. Fischer, S. Ossokine, H. Pfeiffer (Max Planck Institute for Gravitational Physics), T. Vu. Numerical-relativity simulation: S.V. Chaurasia (Stockholm University), T. Dietrich (Potsdam University and Max Planck Institute for Gravitational Physics) But it’s not just mergers that create gravitational waves that we can measure. There are also continuous gravitational waves sources, produced by a single object which is both massive and spinning. The irregular shape of the star (with various imperfections) will lead to gravitational waves, but of a single frequency (regularity of the wave) and amplitude (strength of the wave). One method is by looking at pulsars (neutron stars who’s poles regularly point in the direction of the observer: us) to see if the radio pulse, which is sometimes more accurate than atomic clocks, would arrive at irregular intervals due to the warping of spacetime by gravitational waves (which warps light). One such project hoping to observe just this is the Pulsar Timing Array, involving 8 radio telescopes around the world, from the Lovell Telescope a few miles down the road, to the Green Bank Telescope in the USA. It could also be seen as a continuous signal, or pitch, if it were observed by LIGO or Virgo [14][6]. But we can’t forget the last, or more correctly first, to the party: stochastic gravitational waves. These waves are small and come from all directions, known as a Stochastic Signal (a signal with a random pattern which can’t be precisely predicted), and are thought to originate from the Big Bang. Unlike the CMBR (Cosmic Microwave Background Radiation) which originate from when light could pass through matter without being reabsorbed 380,000 years after the Big Bang, these stochastic gravitational waves propagated out due to the events that happened during the Big Bang, meaning that, if we can observe them, we could see further back in time than ever before [6][15]. There is just one more type that tags on the end, called burst gravitational waves. These don’t have a specific source as such, and aren’t well understood at all. However, we do know that they’re random events with no way to predict how they’ll act. This is simply the ‘other’ category in the list of types of gravitational waves, highlighting just how new this branch of astronomy is and how much we still have to learn about gravitational waves [6]. The stellar graveyard of black holes and neutron stars detected by LIGO and Virgo, including the two neutron star-black hole mergers highlighted in the centre (the lines show the two objects which then merge to form a product: the one at the top) Credit: Credits: LIGO-Virgo / Frank Elavsky, Aaron Geller / Northwestern University. Hopefully, as many more observations are made of these illusive events, we will be able to build a better picture of our Universe, far beyond the constraints of the traditional light based astronomy, so we can understand what really happened at the beginning of the Universe, and more about neutron stars and black holes: objects that we still don’t understand due to the constraints of the electromagnetic spectrum. by George Abraham, ADAS member. #GravitationalWave #BlackHole #NeutronStar #CMBR #Nucleosynthesis #JodrellBank #LIGO #Virgo Click here for the previous news article Click here for the next news article Click here to listen to the first observation of gravitational waves (made by two black holes merging) and here to watch a simulation of it. Click here to listen to the first observation of gravitational waves produced by a neutron star merger and here to watch a simulation of it. Click here to listen to what Stochastic Gravitational Waves are thought to sound like Click here to listen to what Continuous Gravitational Waves are thought to sound like and here to watch a simulation of it. Click here to watch a simulation of a neutron star black hole merger Click here to listen to other gravitational wave observations by LIGO and Virgo Click here to see the interactive LIGO-Virgo Compact Binary Catalogue by the University of Cardiff Click here and here for iPhone apps, and here for an Android app to get alerts to each detection of gravitational waves, so you can know when the spacetime is warping around you. References "Science Bulletins: Gravity-Making Waves". American Museum of Natural History, YouTube. Archived from the original on 3rd July 2021. "Gravitational wave signatures of exotic compact objects". Galileo Galilei Institute. Archived from the original on 3rd July 2021 "Gravitational waves from inspiraling binary black holes". Core. 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"Scientists catch 1st glimpse of black holes swallowing a neutron star". Space.com. Archived from the original on 3rd July 2021. "How much Energy does the Sun Produce?" Learn Astronomy HQ. Archived from the original on 3rd July 2021. "The Invisible Colours of the Universe: Gravitational Waves - Fast Forward Science 2013". Pablo A. Rosado, YouTube. Archived from the original on 3rd July 2021. "How did the first element form after the Big Bang?" Astronomy.com. Archived from the original on 3rd July.

The Cosmic Dawn The Big Bang: the dawn of time; the dawn of space; the dawn of everything we know today. However, it wasn’t until much much later that the first light mustered its way out of a star to hail what is known as the Cosmic Dawn. A recent study by researchers at UCL and the University of Cambridge has determined the date of this event to be between 250 million and 350 million years after the Big Bang. So how did this Cosmic Dawn come about, and why is this information so important? [1] Artist's concept of the first population III stars Credit: NASA/WMAP Science Team The Prologue The run up to the Cosmic Dawn is the story of how the first atoms of hydrogen came together into a population III star: the ‘purest’ of stars, made almost exclusively out of hydrogen and helium. After the Big Bang, when all the primordial ions and atoms eventually came into being, the passage of time led to them being pulled into clumps which eventually collapsed to form the hot fusion furnaces that then led to what we see today in the form of our Sun (a population I star, containing heavier elements than population III stars [11]) [2]. The ultraviolet (UV) radiation emitted from these population III stars was enough to excite the surrounding hydrogen gas, leading to that gas absorbing energy. This frequency of radiation absorbed was precisely 1.4GHz (1.4 billion Hertz), leading to a characteristic absorption line in spectra of light from around that time [3]. Then, due to the way in which the Universe is expanding, this absorption line will be observed at a lower frequency (redshifted light). To detect this low frequency signal, a small horizontal antenna was utilised, at just around 2 metres long, called EDGES (‘Experiment to Detect the Global Epoch of Reionisation Signature’: a fancy way of saying “a telescope to find the absorption line left by the first stars”). Even though the signal they were looking for was so far away and so old, theories stated that the amount of UV light emitted by these population III stars was so great that the absorption signal would still be prominent even now, even though noise can be 10,000 times brighter than this signal, which is “like being in the middle of a hurricane and trying to hear the flap of a hummingbird’s wing” according to Peter Kurczynski who oversaw NSF funding of the EDGES programme [4][5][6]. And this turned out to be true when, sure enough, a signal was found at the much lower frequency of 78MHz (78 million Hertz), and a year of doing repeat observations with different variables such as the orientation of the antenna being changed, the lack of a change from that frequency of absorption line was strong evidence for these population III stars and the Cosmic Dawn [7]. EDGES ground based spectrometer Credit: © Copyright CSIRO Australia, (2018) Why is the Cosmic Dawn so Important? The way in which the figure for the Cosmic Dawn (250-350 million years) was worked out was by analysing images not of individual stars but galaxies, taken by the Hubble Space Telescope and Spitzer Space Telescope, due to how bright collections of stars are. The galaxies analysed were 6 of the most distant (and therefore oldest) galaxies known, of redshifts at z ≥ 9 (including: MACS0416-JD, MACS1149-JD1, GN-z10-3, GN-z9-1, GS-z9-1, UVISTA-1212; great names!), calculating how far away these galaxies are from Earth. Then, observing for 70 hours on three Chilean telescopes (the Atacama Large Millimetre Array, the Very Large Telescope, and Gemini South) along with the twin Keck telescopes in Hawaii, they confirmed their age, 550 million years, and from this they could work out when Cosmic Dawn happened [8][9]. It then predicts that the first galaxies could have been formed at a time which will be visible to the new James Webb Space Telescope to be launched in October of this year: something that could unlock many more answers to mysteries about how the early Universe worked, revealing the inner workings of stellar evolution [8][12]. James Webb Space Telescope Credit: NASA The First Galaxies Telescopes have found that the frequency of galaxies rapidly declines after a redshift of z = 6 (around 1 billion years after the Big Bang), coming to 0 at redshift z = 10 (when the Universe was 500 million years old). However, using simulations of the evolution of the 6 galaxies in the study, the researchers discovered that 69% of the stellar mass of the galaxies observed was formed by redshift z = 10, meaning that the time when those galaxies will have finished forming will be visible to the James Webb Space Telescope (hence the prediction in the previous section). Only with these observations will we be able to get a clear picture of how the first galaxies actually formed, and know what actually happened in a galaxy far, far away [8][9][10]. Image of galaxy MACS1149-JD1. Credit: ALMA (ESO/NAOJ/NRAO), NASA/ESA Hubble Space Telescope, W. Zheng (JHU), M. Postman (STScI), the CLASH Team, Hashimoto et al., CC BY 4.0 by George Abraham, ADAS member. #Star #PopulationIII #JWST #HubbleSpaceTelescope #HST #CosmicDawn #BigBang #RedShift Click here for the previous news article Click here for the next news article Click here to watch the video on the discovery of the absorption line at 78MHz Click here to see the paper on the discovery of the date of the Cosmic Dawn Click here to see where MACS0416-JD is; here for MACS1149-JD1, here for GN-z10-3, here for GN-z9-1, here for GS-z9-1, and here for UVISTA-1212 References "Cosmic dawn occurred 250 to 350 million years after Big Bang". UCL. Archived from the original on 27th June 2021. "The First Stars and Galaxies". Uppsala Universitet. Archived from the original on 27th June 2021. "Fingerprinting the very first stars". Astronomy.com. Archived from the original on 27th June 2021. "The birth of the first stars". YouTube, National Science Foundation. Archived from the original on 27th June 2021. "Astronomers detect ancient signal from the first stars in the universe". National Science Foundation. Archived from the original on 27th June 2021. "Experiment to Detect the Global EoR Signatures (EDGES)". LoCo Lab. Archived from the original on 27th June 2021. "EDGES: Experiment to Detect the Global EoR Signature". MIT Haystack Observatory. Archived from the original on 27th June 2021. "Astronomers work out when the first stars shone". BBC News. Archived from the original on 27th June 2021. "Probing cosmic dawn: Ages and star formation histories of candidate z ≥ 9 galaxies". Monthly Notices of the Royal Astronomical Society. Archived from the original on 27th June 2021. "The First Galaxies". UCL. Archived from the original on 27th June 2021. "What Kind of Star is the Sun?" Universe Today. Archived from the original on 27th June 2021. "webb". ESA. Archived from the original on 27th June 2021.

Let’s Start at the Very Beginning… 13.7 billion years ago the Big Bang happened: the birth of the Universe. The building blocks of nuclei (protons and neutrons) formed, before combining to form the nuclei of the first elements of the Universe. However, the temperature and pressure of the Universe was so high atoms couldn’t form, since electrons weren’t able to combine with the nuclei. Instead, a hot ionised plasma fog was formed, scattering radiation with each forced separation of electrons from a nucleus. This then created an impenetrable wall of radiation which lasted for 380,000 years, before it was then cool enough for electrons to finally meet with nuclei to form neutral atoms (the epoch of recombination - the biggest reunion in the history of the Universe, it could be said). This radiation left a mark on the Universe, still visible to this day in the form of the Cosmic Microwave Background Radiation (CMBR) [1][2]. The CMBR is the key to understanding everything that comes later. Hidden within it are seemingly random fluctuations in the amount of radiation emitted: the weaker the radiation, the more the photons had to fight their way through the impenetrable fog and loose energy because of it, meaning weaker radiation shows denser areas of matter. And these minute fluctuations in density, quantum fluctuations, were formed in random incidences in the first event of rapid inflation in the 0.00000000000000000000000000000001 seconds (that’s 32 zeros: a one hundred-nonillionth), with an increase in size by a factor of 1,000,000,000,000,000,000,000,000,000,000 (1 with 30 zeros: a nonillion). This increase dramatically amplified the small quantum fluctuations to an enormous scale, leading to denser areas of matter and sparser areas of matter. The denser areas then became denser and denser due to gravitational attraction, leading to what we see today: the cosmic web [3]. The Cosmic Microwave Background Radiation (CMBR) Credit: NASA/WMAP Science Team Universe Wide Web Over the next 13.7 billion years or so, these quantum fluctuations kept on amplifying, ordering objects, such as galaxies, into thick long strings (filaments), creating voids of near-empty space (where the laws of physics may not be the same as here on Earth). These filaments then condensed into large galaxy clusters, which are where galaxy groups (such as the Local Group, made of galaxies such as the Milky Way, Andromeda, and Triangulum) congregate, making up thousands of galaxies with a collective mass of between 100 trillion and 1 quadrillion times the mass of our Sun, and around 30 million light years across [4]. As time goes on, the filaments will feed into the galaxy clusters, forming galaxy superclusters, at more than 100 million light years across. Eventually, these superclusters will become islands of galaxies, separated by voids of very low density, containing isolated stars and galaxies[4][5] There’s one problem though: there’s not enough stuff to produce that much of a pull to create such structures. Computer simulation of the 3 Universe, at 3 billion years old, where filaments and voids are forming, along with areas of slightly higher densities: galaxy clusters. Credit: ESO, CC BY 4.0 The Invisible Web The answer lies in dark matter. Making up 27% of the Universe and 80% of matter in the Universe, dark matter creates a skeleton for the cosmic web to form around. And around galaxies dark matter clusters further, creating dark halos (the Milky Way has a halo which is 300,000 light years across, and possibly even further -the Milky Way itself is only 100,000 light years across), linking galaxies together gravitationally [6][7][8][9][10]. But, if it’s invisible, how come we’ve got pictures of it? There are a number of methods. Chandra X-Ray Image of Abell 2029: a cloud of hot gas where multiple galaxies lie. Credit: NASA/CXC/UCI/A.Lewis et al What’s not there? The first method is to observe how the stars and gas within galaxies move about. If the amount of matter which can be seen doesn’t account for how the stars and gas move, then there’s something at play, and that something could be dark matter. The higher the speed of motion, the greater the mass there is to pull those objects around the galaxy [8]. This can then be applied to much much larger scales, such as galaxy groups or clusters. If the speed of the galaxies that make up the groups and clusters are so high that, theoretically, they should fly out of the group or cluster, it could be dark matter that’s keeping everything together. In fact, this particular theory explains how the gravitational pull between the nearby Andromeda Galaxy and the Milky Way is so strong as to pull them together to then collide in 3 billion years [8][10]. Then there’s the observations of high energy X-rays, which are emitted from gases found throughout galaxy clusters. The gas physically shouldn’t be emitting that much energy, sometimes exceeding a million Kelvin (around a million ºC), but instead drifting away from the galaxy clusters and evaporating. However, a dark source of extra gravitational pull seems to be holding this gas together: dark matter [8][11]. And then there’s gravitational lensing: an effect whereby the light from something behind a place with a strong gravitational field distorts and magnifies that light behind, sometimes even creating multiple images of the same thing. The are various effects involving this, including rings, crosses and arcs. If there’s no obvious source of mass distorting the light, one source could be dark matter [12][13][14]. The Einstein Cross: four images of a distant quasar, being an effect of the gravitational lensing of a nearby galaxy. Credit: NASA/ESA/STScI The Map Using the gravitational lensing technique, along with some handy artificial intelligence to look at the 100 million galaxies in the data set, the Dark Energy Survey (an international collaboration to survey the night sky and uncover the secrets of dark energy and dark matter) were able to produce a map of the dark matter in a quarter of the southern hemisphere’s sky. There are two key findings that were produced from the paper behind this magnificent map (the largest dark matter map made using gravitational lensing). First is that the dark matter in our Universe is smoother than computer simulations expect (using equations from the standard model: the model from Einstein’s theory of general relativity), suggesting there may be something missing in the maths. The next is that we now know exactly where the voids are in that part of the sky (since they’re more obvious when looking specifically at the layout of dark matter), meaning we can point our telescopes there to see if physics seems to work any differently, and if so, how [9][15][16][17][18]. Map of the optical Gaia sky overlaid with the map of dark matter, showing: filaments, voids, and halos (where galaxy clusters lie) Credit: N. Jeffrey/Dark Energy Survey Collaboration Hopefully this discovery, along with many more to come, will open the horizons for more meaningful observations of the Universe, so we can get a broader view of how our Universe functions and find out what dark matter actually is. by George Abraham, ADAS member. #DarkMatter #CMBR #CosmicWeb #Halo #DES #GravitationalLensing #GeneralRelativity #StandardModel #Filament #GalaxyGroup #GalaxyCluster Click here for the previous news article Click here for the next news article Click here to look at the paper behind the map Click here to watch the video to learn more about the papers released by DES, and the enormity of the project, and here for a more in-depth view Click here to look at the other papers produced in the DES Year 3 cosmology analysis Click here to look at galaxy cluster IDCS 1426, here to look at the Einstein Cross and here to look at the sheer number of galaxies in Abel 2029, all on ESA Sky Click here for an activity by JPL to simulate how we detect dark matter in the Universe. References "How did the first element form after the Big Bang". Astronomy Magazine. Archived from the original on 29th May 2021. "Cosmic Microwave Background". Swinburne Astronomy Online. Archived from the original on 29th May 2021. "The cosmic microwave background and inflation". ESA. Archived from the original on 29th May 2021. "Galaxy Cluster". Universe Today. Archived from the original on 29th May 2021. "'We Don't Planet' Episode 7: The Vast Cosmic Web". Space.com. Archived from the original on 29th May 2021. "Dark matter". CERN. Archived from the original on 29th May 2021. "New Map of Local Dark Matter Reveals 'Bridges' between Galaxies". Sci News. Archived from the original on 29th May 2021. "Dark Halo". Swinburne Astronomy Online. Archived from the original on 29th May 2021. "New dark matter map reveals cosmic mystery". BBC News. Archived from the original on 29th May 2021. "Hyperfast Star Was Booted From Milky Way". NASA. Archived from the original on 29th May 2021. "Study Suggests Andromeda Crashed into the Milky Way 10 Billion Years Ago". SciTechDaily. Archived from the original on 29th May 2021. "7 Incredible Discoveries from two Decades of X-Rays". Sky & Telescope. Archived from the original on 29th May 2021. "Gravitational Lensing". Hubblesite. Archived from the original on 29th May 2021. "Ask Astro: If dark matter is invisible, then how do we detect it?". Astronomy Magazine. Archived from the original on 29th May 2021. "Astronomers have created the largest ever map of dark matter". NewScientist. Archived from the original on 29th May 2021. "Astronomers create largest map of the universe's dark matter". The Guardian. Archived from the original on 29th May 2021. "Overview". The Dark Energy Survey. Archived from the original on 29th May 2021. "DES Year 3 Cosmology Results: Papers". The Dark Energy Survey. Archived from the original on 29th May 2021.

Element Nucleosynthesis Elements; the building blocks of what makes up: us, the Earth we live on, and the entire Universe. They shape everything that happens throughout each day of our lives, from the copper supplying our energy; to the lithium storing it; and the oxygen we breathe. However, they haven’t been here forever. Through processes of nucleosynthesis (creating new nuclei of atoms from the protons and neutrons that make them up) which have happened and are happening throughout the Universe, we are able to live the way we do. These processes include: big bang fusion, cosmic ray fission, neutron star mergers, explosions, and dying low mass stars (as well as many other methods, including in particle accelerators here on Earth) [1]. Colour coded periodic table showing the origins of elements in the Solar System. Credit: Jennifer Johnson, CC BY-SA 4.0 The Big Bang We start our elementary journey at the beginning of time; the beginning of everything: the Big Bang. An event so powerful the effects are still seen today in the form of the Cosmic Microwave Background Radiation (the remains of the Big Bang, emanating from the voids of space at the freezing 2.7 kelvin: 2.7ºC above the coldest possible temperature [2]), the Big Bang emitted so much energy that it’s no wonder some crazy things went on back then. Over the first 3 minutes after the beginning of the Universe (starting at the Universe’s spritely age of 1 second), the first elements came into being: hydrogen (specifically deuterium -a neutron and a proton- and tritium -two neutrons and a proton-), helium (helium-3 and helium-4 to be precise), lithium (lithium-7) and beryllium (beryllium-7). And they all came into being through fusion: the smashing together of particles and atoms to make atoms of elements with higher masses. In fact some of the deuterium, helium and lithium from the Big Bang (known as primordial elements) is still around in the Universe today, as a 13.7 billion year old relic of the Universe’s past. However, the same cannot be said for the beryllium and tritium, with half lives (the time it takes for an atom to decay by half into another element) of just 53 days and 12 years respectively. The Cosmic Microwave Background Radiation (CMBR) Credit: NASA/WMAP Science Team Cosmic Rays The Universe is therefore full of hydrogen and helium… but not lithium. The third element in the periodic table and one of the three to have braved 13.7 billion years of time to be here today is not a very abundant element, yet, generally speaking, the lower (the less protons) in the periodic table an element is, the more of it there is. So why is lithium an exception? The real amount of lithium made in the Big Bang was a feeble 0.0000001% (a ten millionth of a percent) of the Universe’s elements at the time (as opposed to the ~75% hydrogen and ~25% helium). In other methods all involving stars (which we’ll talk about later), lithium (along with beryllium and boron) also can’t be created in the same quantities we see it in today. Instead, enter cosmic ray spallation [4]. When cosmic rays (usually high energy neutrons) collide with an atom’s nucleus, multiple particles from that nucleus are released, which then begin a chain reaction of more and more collisions and emissions of particles, known as a cosmic ray cascade. And this isn’t even the best part! The particles, or spalls, that fly out from the atoms which have had a collision are then absorbed into an atom, creating a new isotope (a new number of neutrons in the atom) or even a new element (a new number of protons in the atom), leading to lithium, beryllium and boron being formed. [5][6][1]. There’s only one problem though. Lithium-6 is the isotope made by cosmic ray spallation; not lithium-7: the most common type, and also the type made in the Big Bang [7]. Artist conception of showers of cosmic rays passing through Earth's atmosphere. Credit: Simon Swordy (U. Chicago), NASA Explosions and Mergers Jumping to the much larger scale, r-process nucleosynthesis is the source of many useful elements we see in the Universe, and on Earth, today, including the likes of: gold, silver and iodine (all useful to us in many ways) [7]. And there are two ways r-process nucleosynthesis could occur: neutron star mergers and supernovae [8]. Supernovae are by far the most famous method of the two. As massive stars (greater than 9 times our Sun’s mass) come to the end of their lives as burning giants, they begin to collapse at around a quarter of the speed of light at their fastest collapse, before bouncing outwards, splurging neutrinos and gases into the surrounding environment in a shockwave (moving at up to a tenth of the speed of light), beginning nuclear fusion, whereby atoms fuse to make heavier and heavier elements. This then breaks out into a full blown supernova, where the star shines at around 10 billion times the Sun’s brightness (brighter than whole galaxies) to leave a core behind. However, it’s the hot bright phase that is the most important: a flurry of rapid neutron captures (the ‘r’ in ‘r-process’ is for ‘rapid’) occur, where neutrons enter atoms to turn them into larger and larger isotopes of their element. However, this only happens to a point, since the nucleus of the atoms (what is receiving the neutrons) reach neutron drip. This is where the forces holding the neutrons together in the atom’s nucleus stars to decrease and become negative, stopping any more neutrons from entering. Beta-minus decay then occurs, where the neutrons change into protons, both increasing the number of neutrons that can enter the atom (since there’s now less negative charge because of the proton’s positive charge) and increasing the atom’s atomic number, creating heavier and heavier elements [9][10]. This isn’t it for the massive stars though! Instead, those that are on the less massive range turn into neutron stars: stars made of protons and electrons which are crushed together so much they turn into neutrons. In fact, they’re so compressed just one sugar cube sized piece would weigh as much as 1 trillion kilograms (or one seventh the mass of Mount Everest [11][12]) [11]. And this abundance of neutrons can only mean one thing: rapid neutron capture. When two neutron stars merge (having pulled each other closer by their immense gravitational attraction -I know, so romantic!) the r-process kicks in, creating many more useful elements and throwing them out into the Universe to become, along with what's produced in Supernovae, what’s in our smartphones and what’s in our sushi [13]. Type 1a Supernova SN 1994D (bottom left) near galaxy NGC 4526 Credit: NASA/ESA/ The Hubble Key Project Team/ the High-Z Supernova Search Team, CC BY 3.0 A Bit Closer to Home Low mass stars (such as our Sun), unlike the massive stars that have their destiny making high mass elements, have more humble, yet arguably more important, destinies. All these low mass stars burn through hydrogen but, unlike the modern fuel source hydrogen has come to be here on Earth, they fuse it to get energy; a lot of energy! Apart from energy though, this fusion of hydrogen atoms forms helium, leading to hydrogen and helium being the most abundant elements in the Universe (though not on Earth, since they are very good at escaping due to their low masses). Once all the hydrogen has been eaten up though, a star’s next meal will be the heavier elements, all the way up to iron [14]. Why stop at iron though? This is because it takes more energy to fuse than what the fusion process produces, resulting in there being not enough energy to sustain a star, leading to its collapse. However, our Sun, along with many other low mass stars (less than 9 times the mass of the Sun) will stop much earlier (somewhere around carbon), forming a red giant [15][16]. That said, they may have a few more elements in them, forming by the s-process (’s’ for ‘slow’). This process involves neutrons which are emitted (or liberated) from neutron rich atoms like carbon-13 and neon-22, before being captured by other atoms and turning into protons (through beta-minus decay) to create new elements (up to lead) This is the slow process though, taking place over thousands of years instead of the seconds that the r-process takes [17][18]. Eventually, this excess mass accumulating around the red giant is blown away in a planetary nebula, leading to a white dwarf. This white dwarf is then the source of the majority of the lithium in the Universe (25%) due to novae: the emission of a bit of the white dwarf due to the absorption of some hydrogen from a nearby star, leading to the white dwarf emitting a lithium producing isotope in the process [19]. GK Persei Nova Remnant. Credit: X-ray: NASA/CXC/RIKEN/D.Takei et al; Optical: NASA/STScI; Radio: NRAO/VLA Cold Metal Why have I been going on about the formation of elements though? It all comes down to the recent news which has come from ESO (the European Southern Observatory), who have provided the data for a study by a Belgian team of scientists who discovered iron and nickel vapours on the surface of comet C/2016 R2 (PANSTARRS), 480 million kilometres from the Sun, where they’ve never been observed before due to the expectation that only hot environments would provide the correct temperatures for the vaporisation of these heavy metals. Iron, with atomic number 26, and nickel, with atomic number 28, are inherently formed in different ways and therefore, most importantly, in different quantities. So, you’d expect lots of iron and a bit less nickel (10 times the amount of iron to be precise). However, through spectroscopy, the chemical signatures of iron and nickel were found in equal amounts! What’s more, the interstellar comet 2I/Borisov is also showing similar amount of these two elements, therefore hinting that both comets were formed in similar environments, suggesting that what we see in our Solar System is a good template for what’s seen in other parts of the galaxy, and maybe even the Universe; whilst also bringing up the question of why there is this equal amount of nickel and iron seen on comets [20]. Heavy metal detection in the atmosphere of comet C/2016 R2 Credit: ESO/L. Calçada, SPECULOOS Team/E. Jehin, Manfroid et al., CC BY 4.0 by George Abraham, ADAS member. #Element #Nucleosynthesis #Comet #Spectroscopy #Neutrino #Neutron #Proton #Supernova #NeutronStar #CosmicRay #BigBang Click here for the previous news article Click here for the next news article Click here to watch an animation of the heavy metal composition of comet C/2016 R2 (PANSTARRS) Click here to find out where comet 2I/Borisov is on its journey out of the Solar System, and here to look where comet C/2016 R2 (PANSTARRS) is on its orbit References "The Origin of Elements". The Ohio State University. Archived from the original on 22nd May 2021. "Lecture 31: The Cosmic Microwave Background Radiation". University of Alberta. Archived from the original on 22nd May 2021. "How the Big Bang forged the first elements". Astronomy.com. Archived from the original on 22nd May 2021. "This is Why Three of the Lightest Elements are so Cosmically Rare". Forbes. Archived from the original on 22nd May 2021. "Cosmic Rays". 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The Interstellar Medium At 153 AU (153 times the average distance from Earth to the Sun) and counting [1], Voyager 1 is a long, long, long way away. And at these astronomical distances there are things that can be observed which can’t be observed with precision within the reach of the Sun (the heliosphere), namely the interstellar medium. This is made up of all the low density gas and dust that fills the area between stars: 99% interstellar gas and 1% interstellar dust, making up 10-15% of the Milky Way visible from Earth [2][3]. And this concoction of material has recently been directly observed by the Voyager 1 probe, but before we delve into the findings, let’s have a look at the science behind the interstellar medium. Survey of the ionised gas in the Milky Way, surveyed by WHAM (Wisconsin H-Alpha Mapper) Credit: Haffner, L, et al. (2003), funded by the NSF Interstellar Gas The lion’s share of the interstellar medium is taken up by interstellar gas: a mixture of some helium (10-25%) and a lot of hydrogen (75-90%). However, it’s not the even and perfect spread of the odd atom or two in a partial vacuum that you might expect. Instead, both temperature and pressure can vary vastly, with temperatures ranging from just a few ºC above absolute zero (the coldest temperature, where no energy is released), to millions of ºC above absolute zero (i.e. millions of Kelvin, shortened to K); and pressures ranging from just one atom in a cubic centimetre of space, to enough atoms to block the light behind it. There are generally four forms of interstellar gas, the first being cold (around 100K), neutral hydrogen clouds (called HI regions, pronounced “H-one”). This is what most interstellar gas is, but due to its cold temperature, it’s not the most visible, since there needs to be some energy to emit light. However, there’s help in the form of absorption, where particular wavelengths of light passing through the cloud are absorbed, leaving characteristic absorption lines (gaps) in the spectra of light emitted from stars (creating absorption nebulae when in high concentrations). The Lockman Hole, where redder light is taken out by the HI region to give astronomers a clearer view of the bluer light. Credit: Chandra X-Ray Observatory, NASA Then theres the hotter (10,000K) ionised hydrogen gas clouds (called HII regions, pronounced “H-two”). Like HI regions, HII regions absorb light, but because HII regions can absorb so much energy from near by hot stars, they emit light (through a process of electrons loosing the energy they absorbed from nearby stars and emitting photons -light), creating characteristic emissions lines (most notably the red H-alpha, Hα, line) in the spectra of these objects (making emission nebulae when in high enough concentrations). The Orion Nebula (an HII region and emission nebula). Credit: NASA/ESA/M. Robberto (Space Telescope Science Institute/ESA)/Hubble Space Telescope Treasury Project Team Then there’s the even hotter interstellar gas (millions of Kelvin) made of not just hydrogen but some oxygen, and not even the normal oxygen we breathe: oxygen with 5 electrons missing. What’s more, the gas emits not low energy red Hα light, but very high energy X-rays. But how? The answer lies in the high energy supernovae explosions (a stage towards the end of a star’s life) which eject gas at fast speeds of tens of thousands to millions of kilometres per hour, heating the interstellar gas it comes into contact with and creating these high energy gas clouds. Vela Supernova Remnant (one of the largest x-ray features in the sky) Credit: Harel Boren, CC BY-SA 4.0 Extremely cool (10K) molecular gas clouds are the last type, made up of not individual atoms, but molecules such as CN (cyanide, made of carbon and nitrogen) and CH (hydridocarbon, made of carbon and hydrogen), as well as CO (carbon monoxide, made of carbon and oxygen) and many other molecules. Like the HI regions, they absorb light at specific wavelengths which correspond with the atoms present, and, if the gravitational pull is strong enough, these regions can grow into complex and colourful clouds of interstellar gas [3][4][5][6]. Taurus molecular cloud, glowing due to star formation within the cloud Credit: ESA/Herschel/NASA/JPL-Caltech/R. Hurt (JPL-Caltech), CC BY-SA 3.0 IGO However, how can these interstellar gas clouds contain molecules when they’re bombarded by high energy rays such as ultra-violet (UV) light which splits apart such molecules? The answer lies in the important and complex world of interstellar dust; the next stop on our journey. Interstellar Dust Unlike the dust you tried to get rid of when you were doing a bit of spring cleaning, this dust is a bit more ‘space-age’. Interstellar dust (not to be confused with interplanetary dust or galactic dust) is made of carbon, iron compounds, silicates, and/or ice, measuring just 0.1 microns (a 750th of the width of a human hair) across and taking irregular shapes. Due to the solid form of dust, if it collects into high enough densities, it can scatter the light through extinction. This is where the size and density of the dust comes into play, with most interstellar dust being the size which can scatter bluer light (such as the UV light which can split apart molecules), removing this light to create an appearance that the dust is red: interstellar reddening (not to be confused with redshift). This then protects those all important gas molecules in molecular gas clouds. Barnard 68, also known as the Bok globule, shows interstellar reddening through the red infrared section in the centre Credit: ESO, CC BY 4.0 However, if it is in high enough concentrations (100-1000 grains per cubic centimetre), then all the light from behind the dust is absorbed, creating dark nebulae (seen as patches of perfectly dark sky with no stars). Barnard 56, also known as the Pipe Nebula, is a dark nebula Credit: ESO, CC BY 4.0 The dust doesn’t just affect the light passing through it, but also the light being directed onto it. It reflects this light, creating reflection nebulae [3][7]. Reflection nebula Messier 78 in Orion Credit: ESO/Igor Chekalin CC BY 4.0 However, we don’t just observe these wonderful and complex nebulae from afar; there’s a cloud going through our own Solar System right now. Aptly known as the Local Galactic Cloud, it creates a constant flow of particles, known as interstellar wind, coming from the middle of the constellations of Sagittarius, Scorpius, Libra and Ophiuchus. This then shows the direction of the movement of the Solar System relative to the cloud, which we’re moving through at 80,000kph (with the location of the source of wind having changed by 4 to 9 degrees within 40 years, possibly due to the fact we’re near the edge of the cloud and may be experiencing ‘turbulence’) [8]. Direction of the interstellar wind. Credit: NASA/Goddard Space Flight Centre But wait… nebulae? How come interstellar dust and gas can get into these intricate formations instead of becoming an even spread throughout the Universe? Stellar Wind The final piece to this interstellar puzzle lies in stellar wind (not to be confused with interstellar wind): a force which interacts with and shapes in the interstellar medium. It is made up of the high-energy protons and electrons ejected by stars across the Universe, including our own Sun. This fast-moving and energetic stream of particles then ‘blows’ the interstellar dust and gas about to then create the structures we observe today. However, along with interstellar wind, supernovae also play a key role, moving high energy particles at high speeds through the interstellar medium, shaping it and creating HII regions. However, as well as shaping these nebulae, stellar wind adds dust and metals to the interstellar medium, and, along with the numerous stars that ‘die’ and shed their material, help the formation of new stars through creating an environment where gas and dust can compress to trigger star formation [9][10]. The Pillars of Creation (the purple points throughout are new stars forming) Credit: ESO, CC BY 4.0 Observations from the Edge This is where we pick up the story of Voyager 1 and the recent news stemming from its observations. It used its onboard plasma wave instrument to detect the minute densities of plasma (ionised gas, in this case being charged interstellar gas) it’s passing through (unlike previous observations which only looked at specific high energy events). The frequency of the audible signals produced by the plasma suggest an increase in plasma density. This is an observation of specific waves of ‘turbulence’ in the interstellar medium, produced by our galaxy’s rotation, as well as supernovae and solar eruptions (such as Coronal Mass Ejections or CMEs). These measurements will then help scientists map out the interstellar medium around our own Solar System [11]. The continuous weak signals (in red) detected by Voyager 1's Plasma Wave Subsystem and filtered through by Stella Ocker Credit: NASA's Voyager 1 Plasma Wave Subsystem/Stella Ocker Hopefully, with much more data from Voyager 1 and 2 to be sent back and processed by scientists on Earth, we will begin to build an accurate picture of how the interstellar medium behaves and what processes drive it. by George Abraham, ADAS member. #Interstellar #Cloud #Gas #Dust #Wind Click here for the previous news article Click here for the next news article Click here to find where Voyager 1 and 2 are currently Click here to see ESO's 3D visualisation of the Pillars of Creation Click here to view the paper published in Nature Astronomy about the detections of waves in the interstellar medium Click here to look at the sky in Hα Click here to look at the Vela Supernova remnant in X-rays, here to look at the Lockman Hole in X-rays, here to look at the Orion Nebula in Hα, here to look at Barnard 68 in near-infrared, here to look at the dark Pipe Nebula, here to look at the reflection of M78 and here to look at the star formation in the Pillars of Creation, all on ESA Sky Click here to listen to the hum of the Universe taken back in 2013 References "Mission Status". 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What are Aurorae? Named after the Roman goddess of dawn, the aurorae are spectacular formations of light that fill the night sky near the north and south poles (sometimes even visible from Timperley). And some spectacular physics is at play here to bring us these wonders of the night sky [1]. It all starts with the Sun, which ejects floods of plasma (charged gas), composed of mostly hydrogen gas which has been torn apart into its constituent protons (positive) and electrons (negative). Known as solar wind, it travels at hundreds of kilometres a second (500 million particles passing a fingertip sized point per second) until some of it reaches Earth’s magnetosphere (its magnetic field). However, this plasma has a secret up its sleeve: the Sun’s magnetic field. This field is then the key into the Earth’s protective magnetosphere: if it has the opposite charge to the magnetic field of the plasma at that point, magnetic reconnection sometimes happens. This is where the two magnetic fields join forces, funnelling the solar wind down a narrow channel. The electrons within the plasma are then shot down along the magnetic field lines towards the poles (known as precipitation). During their transit, they collide with various atmospheric molecules such as oxygen and nitrogen (the two most abundant gases in the atmosphere), exciting some electrons within the molecules (this is where electrons jump further away from their atom, since they have more energy). Then, these electrons shed this excess energy to get back to a more stable position in the atoms which make up the nitrogen and oxygen molecules. As a result, light of characteristic wavelengths is emitted. The most common, green, is due to oxygen; whilst violet, blue and pink aurorae are due to nitrogen (found closer to sea level). However, vibrant red colours are the rarest, produced by oxygen high up in the atmosphere (only emitted when the aurorae are particularly strong, because of increased solar activity) [2][3][4]. Aurora Borealis in Lapland. Credit: Well Lucio, CC BY-ND 2.0 A Clap of… Aurorae? The complex process has many quirks, not least of which is its sound. Research at Aalto University in Finland in 2012 looked into the indigenous Sami people’s claim that the aurorae say ‘klip-klap’. Although they couldn’t prove their claim, when microphones were placed in areas where aurorae are regularly seen, a faint ‘clap-crackle’ was audible (although the sound had to be amplified a lot) and found to be 70 metres from the ground. The cause was found to be large bursts of solar wind which hit charged particles that were trapped in a part of the atmosphere created when it’s a cold night. These particles then discharge and create the ‘clap’ sound. That said, there may be other things at play, since there are a wide variety of sounds created by the aurorae [5][6][7][8][9]. Aurora Borealis from Finland. Credit: Paul Williams, CC BY-ND 2.0 Different Forms Aurorae come in many shapes and sizes, but fit (mostly) into two distinct categories: discrete (an arcing aurora) and diffuse (a pulsating and patchy aurora); both caused by different processes. Discrete aurorae are mostly due to electrons accelerated into the atmosphere by the morphing of Earth’s magnetosphere by the solar wind, whilst their discrete counterparts are formed because of the scattering of electrons due interactions with waves of charged particles from the solar wind. Discrete Aurora Arc over Lake McDonald, north west USA. Credit: NPS/Jacob W. Frank However, these two types can take on many different forms due to the different angles the viewer can look at the aurora from: bursts, arcs, rays, patches, twists, curtains, bands and coronae can all be viewed from just two main types of aurorae [10]. Aurora Corona. Credit: Ronnie Robertson, CC BY-SA 2.0 Although, that’s not the whole story! There are two more special types of aurorae, and the first is called the Strong Thermal Emissions Velocity Enhancement, but we’ll call him STEVE. As the name suggests, STEVE is pretty hot, at 3,000ºC. He’s also visible from lower latitudes than the typical aurorae, emitting spectacular purple, and sometimes green, arcs across the sky. STEVE isn’t all that he seems though, because he’s not one but two phenomena: some sky glow and an aurora. The sky glow side is the striking purple streak which is caused by friction of low-energy charged particles bumping into neutral particles (like a lightbulb heating up); whilst the aurora side is the less common green tinge, caused by the solar wind exciting atoms in the atmosphere. Also, even though STEVE has only recently been discovered, he is more common than you’d think, so if you know what you’re looking for you might even be in with a chance of seeing him! [11][12][13][14]. STEVE at Childs Lake, southern Canada. Credit: NASA Goddard Space Flight Centre And then there’s the dune aurora. Most aurorae are vertical, pointing towards the ground below; dune aurorae, on the other hand, are horizontal, moving south towards the equator. The cause, recently confirmed by comparing photography on the ground to satellite data, is an increased density of oxygen due to mesospheric bores: atmospheric waves which become sandwiched in a gap between the mesopause (the boundary between the thermosphere and mesosphere, with the coldest temperatures in Earths atmosphere: -90ºC) and an inversion layer (a place where temperature increases with height, in areas of high pressure), found between 80 and 100km up. This creates the perfect conditions for certain wavelength mesospheric bores to travel horizontally without tapering off, allowing charged particles to interact with the abundant oxygen to produce aurorae. However, these events are pretty rare, but if you’re in the right place at the right time with the right knowledge, they are certainly a natural wonder to behold [15][16][17][18][19][20]. Images of dune aurorae taken by citizen scientists on 20th January 2016: (a) Aurora, Finland, 17:23UT, (b) Engerdal, Norway, 20:13 UT, (c) Karmøy, Norway, around 20:30 UT, (d) the Isle of Mull, Scotland, at 20:57 UT, (e) Lendalfoot, Scotland, 21:15 UT, (f) Rattray, Scotland, at 21:15 UT (g) shows the directions the aurorae were going (a to f, left to right). Credit: Jukka Hilska (a), Knut Holmseth (b), Kjetil Vinorum (c), Graeme Whipps (d), Mark Ferrier (e), Barry Whenman (f), Grandin, Palmroth, Kalliokoski, Paxton, Mlynczak CC BY 4.0 The North-South Divide Charge particles from the Sun are not only funnelled to the north pole, creating the Aurora Borealis (the Northern Lights), but they’re also funnelled into the south pole, creating the Aurora Australis (the Southern Lights). These two events, however, aren’t entirely the mirror image we’d expect. This is because the magnetic field produced by the solar wind doesn’t always line up with Earth’s, thereby sometimes favouring either the north or south pole to travel towards [21]. The aurorae don’t just vary between the north and south though; they vary, as you’d expect, with distance from the poles. The further away you are, the higher the Kp index needs to be for you to have a good chance of seeing them. The Kp index isn’t a bag of nuts, but an index of the disturbances in our magnetosphere by solar wind, helping to predict the aurorae. Kp 0 is little activity (aurorae visible north of Iceland), whilst: Kp 3 is unsettled (visible near Allesund in southern Norway), Kp 5 gives a good chance of aurorae (visible in Orkney), and Kp 9 is an especially large storm, producing strong aurorae (visible in Berlin). However, not everything at the same latitude as Berlin, for example, will get aurorae only at Kp 9, since the aurorae are formed around the geomagnetic poles, which are 10º different to the geographic poles [22]. A great example of when the Aurora Borealis was particularly strong was back in 1859, where they could be observed as far south as Honolulu in Hawaii, at just 21º north of the equator; whilst the most northerly Aurora Australis seen was possibly in 1909, where it was observed in Singapore, just 8º south of the equator (although this is disputed) [23] And, as the Kp index (and history) shows, the further towards those geomagnetic poles you go, the displays get more common, but only to a point. Instead of aurorae occurring directly at the poles (though they do sometimes), they occur in rings known as auroral zones. The boundaries are dictated by a region between an open field line (which stretches off into Space instead of connecting back at the opposite pole) and a closed field line (which connects back at the opposite pole). This gap is where electrons can be fired down to produce the aurorae we know and love [24]. Aurora from Space. Credit: ESA, CC BY-SA 3.0 IGO Hopefully, in this new solar cycle, with increasing amounts of solar wind coming to Earth, some more spectacular events will be visible in the coming years, maybe even from Timperley! By George Abraham, ADAS member #Sun #SolarWind #SolarCycle #Aurora #Steve #Magnetosphere Click here for the previous news article Click here for the next news article Click here to see the map of what Kp index is visible from which places Click here to see images of different types of aurorae which won prizes in the Insight Investment Astronomy Photographer of the Year 2020. Click here to help out in some citizen science, logging any sightings of aurorae to help build a better picture of the science behind them. Click here to listen to the aurorae recorded by the Aalto University. Click here to watch a video of dune aurorae, created by the University of Helsinki Click here to use widgets to find out if the aurorae have a chance of being visible Click here to view aurorae live References "The Aurorae". ESA Kids. Archived from the original on 8th May 2021. "What causes the Northern Lights?" Royal Observatory Greenwich. Archived from the original on 8th May 2021. "What causes the aurora borealis?" EarthSky. Archived from the original on 8th May 2021. "What causes the Northern Lights?" BBC Sky at Night Magazine. Archived from the original on 8th May 2021. "Auroras Make Weird Noises, and Now We Know Why". National Geographic. Archived from the original on 8th May 2021. "Clap Sounds of Northern Lights? - South Source 70m Above Ground Level". 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The Corona The corona is the outermost shell of the Sun; 10 million times less dense than the surface, extending 8 million kilometres into Outer Space and with a temperature of 1 million ºC. However, each of these numbers has a story to tell, since the corona is a very complex, and little understood, part of the Sun’s atmosphere [1][2][3]. One of the reasons for this lack of understanding lies in the first figure: 10 million. The corona isn’t very dense, and is therefore dimmer than the rest of the Sun. This leads to it being washed out by the Sun’s fiery heart and observers on Earth not being able to see it [1]. However, during a total solar eclipse, the corona becomes visible. This is where the Moon is positioned between the Earth and the Sun, leading to the Moon blocking out the majority of the Sun, whilst leaving the corona intact and visible to observers back on Earth. Because of this, many scientists flock to wherever a total solar eclipse is taking place in order to snap up their measurements in the short time they have (a few seconds to 7.5 minutes), before waiting for the next one, which is on average just every 18 months [4][5]! Some scientists are a bit impatient though, so they use a coronagraph to see it, without the need for a total solar eclipse. It uses an occulting disc (an opaque circle) which sits within the telescope, covering the Sun to a similar extent to what the Moon does during a total solar eclipse, but for a much longer time [6][7]. The corona during the total solar eclipse in 2019 at ESO's La Silla Observatory in Chile. Credit: ESA/CESAR/Observatorio Astrofisico di Torino, CC BY-SN 3.0 IGO Windy… in Space! The next figure, 8 million kilometres, was the subject of a discovery in mid 2014 that the solar corona was a lot larger than previously thought. Using data gathered from studying ripples in the Sun’s magnetic field known as Alfvén waves (like sound waves, but oscillating around every 4 hours instead of hundreds of times per second, and are 10 times Earth’s diameter instead of up to 17 metres -audibly [8][1]) caused by interactions of large solar events within the corona. These large events in question come in many forms; most notably though, solar flares and their larger cousins: coronal mass ejections (CMEs). Solar flares are large explosions of energy, whilst CMEs are bubbles of hot gas (plasma) ejected by the Sun: both can cause worldwide blackouts and both are caused by the Sun’s peculiar and dynamic magnetic field [9]. Due to the Sun being an entirely fluid object instead of a rocky body like Earth, it has a complex magnetic field. Individual parts of the field (known as flux ropes [14]) twist and build up energy, before snapping back to become flat again like an elastic band (magnetic reconnection [13]), whilst ejecting plasma in the process, in the form of solar flares and CMEs. However, most of these ejections of magnetic energy aren’t directed at Earth (since their direction is random), but the odd time that it does happen, it creates disruption from as small as a few satellites being damaged, to as large as a worldwide power outage (although this is extremely unlikely) [9][10]. Coronagraph of Coronal Mass Ejection on 23 July 2012, which narrowly missed Earth Credit: NASA/STEREO Too Hot!! The final figure: 1 million ºC This is the corona’s temperature. However, given it’s the outer extremity of the Sun, it’s nearly 200 times hotter than the Sun’s ‘surface’ (the photosphere), at a measly 5,500ºC [11][12]! Seeing as the photosphere is closer to the centre of the Sun than the corona, it would follow that it would be hotter. However, that’s evidently not the case… but why? There are a few theories to explain this. First off is the wave theory. It explains it by saying that the Alfvén waves described earlier are launched at a certain frequency from within the Sun to the corona. This then starts exciting charged particles and thereby heats the corona. And then there’s the mystery of nanoflares: tiny solar flares that are the result of the same process of magnetic reconnection. However, the energy produced then heats up the surrounding environment by accelerating nearby particles. Notably, these two theories do involve similar processes of changes in the Sun’s dynamic magnetic field, and therefore they may not in fact be different processes. Instead, some believe the Alfvén waves are caused by nanoflares, heating the plasma around the event [13]. Excitingly though, there has been a recent development on the nanoflare front to add to the evidence for this theory, under the nickname ‘campfires’. Solar flares may be a million to a billion times their size (at a microscopic 400-4000km in width), and they may only last from 10 to 200 seconds, but when put together there is the possibility that they are responsible for the heating of the corona. ESA and NASA’s Solar Orbiter found around 20,000 campfires in just 70 minutes of observing, meaning this could even be a viable constant source of heat (something people have been searching for for decades). And what’s more, a team at the Max Planck Institute for Solar System Research in Germany, along with a PhD student from Peking University in China, were able to model these campfires and a few of their predictions closely matched observations taken by Solar Orbiter. This meant they could utilise the magnetic field lines used in the model to see how the phenomenon worked, and how viable it would be as the corona’s heat source [14][15][16][17]. Campfires seen on the Sun by Solar Orbiter Credit: Solar Orbiter/EUI Team/ESA & NASA; CSL, IAS, MPS, PMOD/WRC, ROB, UCL/MSSL However, it isn’t ‘case closed’ for the corona’s mysterious heating, since there are still many more observations to be made until we’re certain what the full story is. by George Abraham, ADAS member #Sun #Atmosphere #Corona #SunSpot #SolarFlare #CoronalMassEjection #CME #Photosphere #MagneticField #Plasma #FluxRope #MagneticReconnection Click here for the previous news article Click here for the next news article Click here to see how to observe the Sun safely Click here to watch the campfire magnetic fields in action Click here to see how active the Sun is at the moment Click here to look at what the Sun looks like currently (the penultimate in the slides under "Latest Image of the Sun" is a magnetogram: a view of the Sun's magnetic field), as well as to see other widgets to plan your next astronomy adventure (including the Sun's current activity). Click here to see how many solar flares have recently gone off Click here to see the most recent coronagraph Click here to see where Solar Orbiter is in its journey Click here to see when the next total solar eclipse will be near you References "What is the Sun's Corona?" NASA Science. Archived from the original on 1 May 2021. "NASA's STEREO Maps Much Larger Solar Atmosphere Than Previously Observed". NASA. Archived from the original on 1 May 2021. "The Sun's Corona (Upper Atmosphere)". UCAR Centre for Science Education. Archived from the original on 1 May 2021. "Mysteries of the Sun's Corona Illuminated by Eclipse Data". SciTech Daily. Archived from the original on 1 May 2021. "What are Total Solar Eclipses". TimeandDate.com. Archived from the original on 1 May 2021. "What is a Coronagraph". Space.com. Archived from the original on 1 May 2021. "The World through Sound: Wavelength". Acoustics Today. Archived from the original on 1 May 2021. "Coronal Mass Ejection". 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Trundling Laboratories By far the most famous method of extraterrestrial transport is the rover. Their story starts with the Lunokhod 1 (Луноход meaning ‘Moon-buggy’: very inventive! [1]), which, you guessed it, trundled on the Moon. On 17th November 1970, Lunokhod 1 was put onto the lunar surface in Mare Imbrium (the Sea of Rains), just north of the Copernicus crater, rolling out of the Luna 17 lander. It would become the testbed of rovers to come, on the Moon but also on Mars. With eight wheels and a polonium-210 radioisotope heater (a portable nuclear power station) for when the Sun set from the view of its solar panels, it went a staggering 10km in just 10 months (NASA’s Mars Opportunity rover took 7.2 times longer to do the same distance!). It set a precedent that would be carried forward into future rovers, taking 20,000 pictures and 200 panoramas, and conducting over 500 lunar soil tests [2][3]. Lunkhod 1 from the Lunar Reconnaissance Orbiter. Credit: NASA/LRO Following this space-race icon, NASA brought out their own fleet of lunar rovers in the form of jeep-like vehicles with a pair of seats for Apollo astronauts to sit in, known as Lunar Roving Vehicles (LRVs); no more inventive than their Soviet counterparts! Restricted to a 9.5km radius due to their Portable Life Support System (PLSS), astronauts could ride on the untouched lunar landscape, picking up lunar samples, taking pictures and other scientific measurements along the way. However, can’t a robot do the same [4]? Back then, yes, although the amount taken back robotically then was orders of magnitude less than that of the crewed missions to the Moon, such as the Apollo 15, 16 and 17 missions using the NASA’s LRVs. Luna 20, from the USSR, brought a light 55g of soil down to Earth in February 1972, whilst NASA’s Apollo 15 mission, employing the trusty LRV, collected 77kg (1400 times more than the Soviet’s mission) [5][6]. Apollo 17 LRV with astronaut Eugene A. Cernan. Credit: NASA However, as technology quickly advanced, it became evident that the better way was robotic missions: enter the Mars rover! It all started with the Soviet’s Mars 2 and 3 missions, landing a PrOP-M rover… twice. Launched in May 1971 and arriving at Mars in November and December, Mars 2 and 3 attempted to make the perilous landing onto the Martian surface, but they’d picked the worst date to do it… during one of the worst dust storms in recorded history (unfortunate)! That meant Mars 2 crashed and Mars 3 lasted just 14.5 seconds (thought to be because the lander was blown over). If it were to have gone to plan, PrOP-M would have skated out over the lengthy 15 metre maximum distance (due to its ‘umbilical cord’ like tether attached to the lander), carrying a penetrometer (measuring the strength of the surface below) and gamma-ray densitometer (determining the density of the soil below) [7][8]. Instead of the Soviets taking the title of first Martian rover (although the title for first human-made object on Mars was claimed with the Mars 2 crash landing -take the rough with the smooth [8]), it was NASA with their humble Sojourner aboard the Pathfinder mission that took it. Landing in 1997, Sojourner wondered around Ares Vallis (an ancient, and more importantly safe, flood plain, with lots of rocks to analyse). ‘Barnacle Bill’ was the first rock to be analysed by Sojourner, discovering that silica was present: a compound found in igneous rocks (made at high temperatures), suggesting an interesting geological history on Mars, warranting further study [9]. This call hasn’t been forgotten, with the trusty rover having been used in five NASA missions so far [10]. Sojourner on Mars. Credit: NASA The success of this technology has then lent itself to use on other places apart from the Moon and Mars: namely Mar’s moon Phobos, where the German Aerospace Centre (DLR) are looking to send a four wheeled rover onto the Martian moon to get a better understanding of its origins. The MMX (Martian Moons eXploration) mission is scheduled for a drive on the alien moon in late 2026 to early 2027 [11]. The Phobos Rover. Credit: DRL, CC BY 3.0 DE The Methane Submarine Unlike the Yellow Submarine, this next method of transport hasn’t got a song to go with it, but what it does have is a destination with a very cool name: NASA’s Titan Submarine is going to be immersed into the depths of the Kraken Mare on Titan (one of Saturn’s moons). As a liquid methane sea, the Kraken Mare is a challenge for scientists to model for testing, with nothing remotely like it on Earth. At 1,000km wide and 300m deep, the sea will serve as a fantastic location for the first mission to an alien sea, with the aims of: measuring ocean currents, sampling the liquid to find out its chemical composition, and inspecting the seafloor features [12][13][14]. Titan Submarine. Credit: NASA This mission could be a ‘pathfinder’ for another submarine mission to yet another moon: a submarine set for Europa (a Jovian moon). This mission, not seen as feasible at the moment, could one day wriggle its way through 10-20km of ice into the liquid ocean below to investigate what’s down there. The hope is that extra-terrestrial life could be found, with the ocean being home to not liquid methane but liquid water: an ingredient we know is imperative for life [15][16][17]. NASA’s Europa Clipper (scheduled for a 2020s launch) and ESA’s JUICE mission (JUpiter ICy moons Explorer, scheduled for a 2029 arrival) hope to get a better understanding of this icy moon, to find out if missions such as that of the Europa submarine are feasible, as well as to unlock the deep interior of Europa from above (much cheaper!) [18][19][20]. A Miniture Martian Chopper Another exciting way to travel is, however, closer to the present. The modestly named Mars Ingenuity Helicopter has taken flight as the first helicopter on another planet. Having now carried out two test flights (one on 19th April and the other on 22nd April), the 1.8kg drone has now conquered Mars’ thin atmosphere (at just 1% that of Earth’s) to a 2m height (in its most recent flight), with its 1.2m blades wizzing around at a dizzying 2,500 revolutions every minute (terrestrial helicopters spin at just 400-500 revolutions per minute!). The aim is to help us study cliffs, craters and other locations on Mars that are hard to get to for the traditional rover [21][22][23][24][25][26]. The Ingenuity Helicopter in its second flight. Credit: NASA/JPL-Caltech/ASU/MSSS Again, it will also act as another ‘pathfinder’ mission, leading the way for a possible new mission to… Titan. Apart from liquid methane, Titan also has a really interesting surface. NASA hopes to launch the Dragonfly helicopter in 2026 for a 2034 touchdown, using its flight capability to move between places, with journeys of up to 8km to take samples at each stop, before reaching the Selk impact crater: a location where there’s evidence of past liquid water, along with complex carbon-containing molecules, hydrogen, oxygen and nitrogen (all ingredients for life!). The helicopter could then travel a staggering 175km (nearly double the combined distance all Mars rovers have travelled!), exploring the origins of life as well as the beautiful and complex landscapes of the alien moon [27]. Dragonfly on Titan. Credit: NASA/JHU-APL A Space Bunny! The final category of modes of transport on other worlds is the hopper. Like the rover, the hopper has its sights on the Moon and Mars. NASA have proposed the Mars Geyser Hopper as a potential mission to the Martian south pole. With automatic detection systems in place, the Mars Geyser Hopper may be able to detect the first signs of a Martian geyser beginning to erupt and hop to it, taking images along with a chemical analysis of the plume of material emitted (which is moving at 160km/h up hundreds of metres into the sky). Hundred of geysers have been spotted from orbits of Mars already (with around one geyser found every 2km), caused by the ice at the Martian south pole cap melting during the summer, causing high pressure below the surface [28]. Dark dune spots: a sign of geysers on the polar icecaps. Credit: NASA/JPL-Caltech/University of Arizona And then there’s the University of Manchester’s fleet of hopping robots, hoping to become the mission selected by ESA to explore the lunar lava tube system on the Moon (you can read more here) [29]. However, as there is with all these transport methods, there’s a goal to send a mission to somewhere really exotic, even for space agencies like ESA and NASA: a comet. The Comet Hopper is a concept mission to land on comet 46P/Wirtanen. A Jupiter-family comet orbiting between Earth and Jupiter, comet 46P/Wirtanen has volatiles (molecules which evaporate easily at the outside temperature) within it, not possible to study from Space. The hopper would mean scientists could explore the entire surface of the comet (never done before) and collect some volatiles for future study in a sample return mission. However, it’s the hope that some in-situ physical and chemical testing of the nucleus (the comet’s rocky/icy centre) and inner-coma (the comet’s ‘atmosphere’ of ice, gas and dust produced by the comet’s interaction with solar wind), improving our understanding of these small and difficult worlds to explore [30][31]. NASA's Comet Hopper mission. Credit: NASA/GSFC/University of Maryland There is certainly a lot to look forward to in terms of new Space based transport, along with the discoveries that they bring, and who knows what the future holds for how machine, and human, can get about on other worlds. by George Abraham, ADAS member. #Ingenuity #Perseverance #Apollo #LRV #Lunkhod #Sojourner #Phobos #Mars #CometHopper #Moon #Titan #Saturn #Europa #PrOPM #Comet #Helicopter #Dragonfly Click here for the previous news article Click here for the next news article Click here to discover how to make your own cardboard rover, and here to make your own paper Ingenuity Helicopter Click here to watch a video on the University of Manchester's lunar mission proposal Click here to track comet 46P/Wirtanen on JPL's Small Body Database Click here to watch a video on NASA's Titan Submarine proposal Click here to watch a ride on an LRV as part of Apollo 15 Click here to watch Ingenuity's first flight on Mars, viewed from Perseverance (the rover that Ingenuity arrived to Mars with Click here to look at where the Titan Submarine could be landing, and here for the location of the possible Titan helicopter of its end destination References "Луноход". 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Space Race It was mid-1955 and the USA and USSR were commencing the Space Race: a battle as part of the Cold War, with each side showing how it was better than the other, through technological development on an unprecedented scale [1]. It began with the USSR, a group of communist states with Russia at its heart, responding to the USA’s announcement of their plans to have the first satellite in Outer Space. An arms race had started, where the two countries were trying to make sure they would get the first satellite into Outer Space. That award would go to the USSR in late-1957 with the launch of their small orb, Sputnik 1 (Спутник meaning ‘Fellow Traveller’ [2]), sparking numerous other innovations by both sides, in order to seem more powerful in Outer Space. From the USA’s weather satellite Explorer 1; to the USSR’s Sputnik 5 -not the vaccine- returning the first animals and plants back from Space alive (yes, previous missions did the same but never brought them back alive) including 2 dogs and some plants; to the USSR’s Lunar 1 which inadvertently became the first object to leave Earth’s orbit (it was supposed to go around the Moon, but hey!) [3]. However, there’s one thing that none of them did: send a human into Outer Space. Sputnik 1 Replica. Credit: NSSDC, NASA 4 Years Later… That was until just four years after the first technological feat in the Space Race. In spring of 1961 (60 years ago on Monday 12th April), the 27 year old Yuri Gagarin [4] from a collective farm in Klushino, 200 miles west of Moscow (a town so small the only landmarks on Google Maps today are Gagarin’s house and a mobile network operator [5]) left the place where most life had stayed for billions of years (apart from 3 dogs, some plants and a chimpanzee [3]), seeing a view no human had ever seen before. But how did a person like Gagarin get to such heights? Well, apart from using the spacecraft Vostok-1 (Восток meaning ‘the East’ or ‘the Orient’ [6]) it was Gagarin’s fascination with aircraft from his childhood, building many model aircraft whilst learning about the heroes of the Soviet Air Forces at school after the Second World War. By 16, Gagarin worked at the the local foundry helping him gain a place at a technical school, and then a local flying club in 1955 (the start of the Space Race). Then, just 4 years later he was selected in secret by the USSR to be the first cosmonaut and, they hoped, the first human in Outer Space [7]. And they were, beating the USA’s Mercury mission by 3 weeks [7] (having already been delayed by some months due to safety concerns [8]). However, the USSR were pretty laid back with safety, so the night before the launch, the technicians realised the seat Gagarin would be sitting in for the flight was on the heavy side, so bits were frantically stripped off it [8]. They didn’t just do their homework the night before though; they did it on the day of the exam! Whilst getting ready for takeoff, the technicians couldn’t close the door, so a few screwdrivers later they were ready to launch [7]. As Dr. Who shouts “Geronimo”, Gagarin shot off into Outer Space shouting “Поехали” (pronounced “Payekhaleh” meaning “Let’s Go!”), spending just 108 minutes going around Earth before falling back down and landing in… a random part of the USSR, south east of Moscow and 300km south west of the planned landing site, due to another mistake where the spacecraft went 93km further up than it should have [7]. Vostok-1 flew down to 7km above the Earth’s surface, before Gagarin ejected and parachuted down the rest of the way (they hadn’t quite perfected the art of landing yet!). Falling back down to Earth in a place just south east of Saratov, he was seen by a woman and her granddaughter out planting potatoes in a field. The woman inquired “Have you come from space?” to which Gagarin responded triumphantly “As a matter of fact, I have!” [7] (although the exact conversation is debated [9]) [7][16]. Vostok 1 launching on 12th April 1961, with Gagarin inside. Source: NASA Six Impossible things before Lunch By 10:57am, Gagarin became the first human to have been to Outer Space and back, and all in one morning! The USSR then told the world (having kept the mission a complete secret up to Gagarin’s safe return), making him the figure head of the Soviet space programme, whilst also forcing him to retire from a career in space, instead touring the world [8]. Three months into festivities, Gagarin headed for the UK, invited not by the UK Government, but by a foundry workers’ union in Manchester (honouring his former job). Arriving in Manchester, Gagarin toured the city in an open topped car to crowds of people standing in the pouring rain, since, as he said, “the people have come to see me”. Only then was his popularity noticed by the government and he was pulled down to London to meet the Queen and Prime Minister MacMillan [10]. After his fame, he became deputy director of the Cosmonaut Training Centre, getting himself fit enough to return to Space. However, after Vladimir Komarov’s death in April 1976 during a space mission, the authorities banning Gagarin from space travel (since he was too precious to risk blowing up), although he was allowed to be a flight instructor of jet aircraft, leading to his death in March 1968 at the age of just 34 [10]. Gagarin in Warsaw, Poland, in 1961 on his world tour. Credit: Nieznany/Unknown Space Race after Gagarin Three weeks later, Alan Shepard, Jr. became the second human in Space in a fully televised launch of the Mercury-Redstone 3, staying up for just 15 minutes. These flights then paved the way for five more Mercury launches and NASA’s Gemini and Apollo missions, as well as the Soviet’s Voskhod and Soyuz missions [11]. NASA’s Gemini Programme, happening between 1965 and 1966 (just 1 year after ADAS was founded), helped test lots of things in Space never done before, from spacewalks to docking spacecraft [12]. This programme then led NASA to the Apollo Programme, taking place between 1968 and 1972. Apollo was NASA’s way of outdoing the Soviets’ win in 1961 of getting the first human into Outer Space, carrying out 11 manned spaceflights and moonwalks, including the first manned Apollo mission, Apollo 7 (1968); the first orbit of the Moon, Apollo 8 (1968); the first Moon landing, Apollo 11 (1969); and the last manned Moon landing to date: Apollo 17, backing in 1972 [13]. However, the samples collected by the astronauts on the Moon are still being analysed today, with many discoveries having been made, and many more still to happen. Buzz Aldrin on the Moon as part of Apollo 11. Credit: NASA Meanwhile, the USSR had their Voskhod Programme (1960-1963), with only two missions, but still getting the first spaceflight with more than one person into orbit, as well as the first spacewalk (with Alexey Leonov spending just 12 minutes walking in the voids of Space). However, even that had some problems, with Leonov having to vent some air from his suit to fit into the airlock (although he did have a suicide pill incase that didn’t work) [14]. Then came the Soyuz Programme, still in operation today, with its first manned mission being April 1967, attempting a docking as seen in NASA’s Gemini Programme, but failing, instead taking them to 1969 to achieve. It was then used as a transporter, carrying the a lunar lander into low-Earth orbit in November 1970, and sending the cosmonauts into Space to build the Salyut space stations, the Mir space station, and later the International Space Station (ISS). As well as this, the Soyuz has been a beacon for international cooperation, like the ISS, ferrying crews from five space agencies (NASA, Roscosomos, JAXA, ESA and CSA) from Earth to the ISS, outcompeting the less safe Space Shuttle programme: NASA’s way of building the ISS, sending satellites like the Hubble Space Telescope into orbit, and bringing people to the ISS, although it did have a tendency to blow up, leading to its retirement in 2011 [15]. The International Space Station. Credit: NASA Many more manned space missions are planned in the future, hoping to shed new light on the mysteries of our Universe whilst pushing life’s capabilities to see what we can do. However, all this wouldn’t be able to happen if the continuous battle of the Space Race didn’t take place, with Gagarin’s flight marking the very beginning of this fast and exciting journey of innovation and discovery. by George Abraham, ADAS Member #Gagarin #Cosmonaut #Vostok #Sputnik #Mercury #Apollo #ISS #Mir #Salyut #Voskhod #SpaceRace Click here for the previous news article Click here for the next news article Click here to watch the BBC's report of human spaceflight's 60th anniversary, with footage of the launch and an interview with the granddaughter who was planting potatoes when Gagarin landed in her field. Click here to watch the BBC's archive report from the day the news of Gagarin's return from Space to see the reaction of the public Click here to listen to some interesting accounts from people who took part in different events throughout the Space Race Click here to read another article, focussing more on the space stations, marking 20 years of continuous human occupation of Space. Click here to read another article, looking in part at what advanced of lunar science have happened and are going to happen after the Apollo missions. References "The Space Race". History. Archived from the original on 16th April 2021. "Спутник". OpenRussian.org. Archived from the original on 16th April 2021. "Space Race Timeline". Royal Museums Greenwich. Archived from the original on 16th April 2021. "Yuri Gagarin: 60 years since first man blasted into space". Al Jazeera. Archived from the original on 16th March 2021. "Klushino". Google Maps. Archived from the original on 16th April 2021. "Восток". 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The Oort Cloud Most comets we see originate from one place: the Oort Cloud. It’s a shell of billions to trillions of comets that encompasses the Solar System. In fact, it’s so big that Voyager 1 won’t reach it for 300 years (and the outer edge for 30,000 years), meaning it won’t have enough energy to send back data about it, leading also to no direct observations having ever been taken (or ever to be taken, with current technology) [1][5]. So how do we know it’s there? In 1950, Dutch astronomer Jan Oort theorised a cloud which extends 15 trillion kilometres from the Sun (over 1.5 light years!) because of a type of comet known as a ‘long-period’ comet: those that take thousands of years to orbit the Sun and which don’t come from the Kuiper belt (known as ‘short-period’ comets) which only extends 0.05% the distance of the Oort Cloud [2][3]. Oort noticed some striking features about these long-period comets: their orbits didn’t hint at an interstellar origin (so it’s in the Solar System), they came from all directions (so it’s a sphere), and the furthest point of their orbits (their aphelion) was around 50,000AU (7.5 trillion km) [4]. These long-period comets are arguably more exciting than short-period comets for one special reason: they’re usually pristine, formed at the beginning of the Solar System. “So was everything else in the Solar System” you might say, but unlike other objects orbiting the Sun, like short-period comets, objects in the Oort Cloud are made up of the fragments of planets ejected (many ejected into interstellar space) 4.6 billion years ago during their formation. Known as planetesimals, the ones that managed to keep locked on the Sun’s gravity gained eccentric elongated orbits[5]. Their orbits have then settled out into the Oort Cloud, only to be plucked from there by gravitational forces to become comets, possibly due to the pull of the Milky Way, or the hypothetical object called ‘Planet 9’, several times the size of Jupiter but never directly observed [1]. However, the important point to make is that, because these comets take so long to orbit and they spend so much time so far from the Sun, they barely get tarnished by the harsh solar wind and radiation that create those characteristic tails seen on comets, meaning they’re made up of material from the beginning of the Solar System as it was when it was ejected all those billions of years ago [6]. This can then shine a light onto the formation of the early Solar System, and the formation of life. Diagram of the Oort Cloud showing how big it is in comparison with the orbits of Pluto and other Solar System Objects. Credit: NASA An Ancient Messenger One such object came to within naked-eye viewing distance of Earth back in early 1997: Comet Hale-Bopp. At 4.5 billion years old and with an origin in the Oort Cloud, it was comet Hale-Bopp’s very first close approach to the Sun (perihelion) in its lifetime, taking 2,533 years to do the full orbit (not yet complete) [7][6]. And the fact it’s its first journey is important, since this made Comet Hale-Bopp the most pristine comet ever found, having had very little in the way of solar wind or radiation. How do we know? Using a technique called polarimetry, scientists could measure how polarised the light was (light oriented in one plane) which reflected off the coma (the ‘atmosphere’ of ice, gas and dust produced by the comet’s interaction with solar wind), thereby showing how smooth the coma is and so how much space weathering (solar wind, radiation etc.) the comet itself has experienced over its lifetime: the more polarised the light, the smoother the coma, the less chance the object has come close to a body emitting high levels of radiation before (like the Sun), the more pristine the object [6][9]. This meant that Hale-Bopp’s pristine coma could be observed using infrared spectroscopy (looking at what wavelengths of light has been removed by the coma) to study the make up of the comet, and so what was around in the early Solar System and where the comet originated from. Results showed it originated between the orbits of Jupiter and Neptune before being ejected into the Oort Cloud [7]. Comet C/1995 O1 (Hale-Bopp). Credit: E. Kolmhofer, H. Raab; Johannes-Kepler-Observatory, Linz, Austria, CC BY-SA 3.0 Foreign Time Capsule Comets don’t just come from the Oort Cloud and the Kuiper Belt however; they occasionally make the journey from a totally different planetary system. Discovered in mid-2019, Comet Borisov is the first comet of interstellar origins ever observed, known to be interstellar because of eccentricity: how elongated an object’s orbit is. An eccentricity of 0 is a perfect circle around the body it’s orbiting; an eccentricity of 1 is very elongated but not too much as to not orbit the object at its perihelion; and an eccentricity of greater than 1 is an orbit which is so elongated that the object will only be going around the body at the perihelion of its orbit once, meaning its origins are interstellar: Borisov had an eccentricity of more than 3 [8]! However, that’s not the only secret Borisov had hidden up its sleeve: the light reflecting off its coma was recently found to be the most polarised ever observed. This means that it is the most pristine comet ever observed [9]. Put the two facts together and you get an untouched artefact from another planetary system emitting gas and dust which was collected when that planetary system was forming, thereby showing astronomers here on Earth what another planetary system’s early formation was like. Scientists have so far found Borisov’s coma is made up of compact pebbles around 2mm wide, as apposed to the comae from long period comets originating from this Solar System, which are made of irregular bits of material from 2mm wide to 1m wide. This suggests that Borisov’s home planetary system witnessed large impacts which crushed matter into the small dense pebbles observed [10]. Comet C/2019 Q4 (Borisov). Credit: ESO/O. Hainaut, CC BY 4.0 An Interstellar Boomerang Comet Borisov isn’t the only interstellar messenger we’ve come across though. There’s one more in the from of the asteroid ‘Oumuamua (Hawaiian for “a messenger from afar arriving first” [14]). ‘Oumuamua is an asteroid with a few differences: first off, its shape. ‘Oumuamua was observed with large fluctuations in its brightness over time, suggesting the asteroid’s length (800 metres) is up to 10 times its width. As well as this shape, the changes in brightness suggest it doesn’t rotate on one axis like most objects in the Solar System: it tumbles, completing 1 rotation every 7.3 hours by moving on 2 axes. It’s also outgassing material: something usually seen on comets, leading it to be categorised as one at first. Although the asteroid was a long way from Earth, even from its closest approach (leading to observations of a small coma being unlikely), ‘Oumuamua was seen to be accelerating in a different way to the one expected (meaning earlier predictions of its trajectory were wrong), suggesting an outgassing of material. Despite this, it was reclassified as an asteroid since a coma was not visible, leading to Comet Borisov being the first interstellar comet to be observed. Moreover, since ‘Oumuamua has no visible coma, it’s a lot dimmer than Borisov, meaning that after January 2018 it became invisible to all telescopes on our planet (although current predictions say its currently just past the orbit of Uranus [13]) [11][12]. Combined image of 1I/2017 U1 (`Oumuamua) (in blue) observed by the Very Large Telescope and Gemini South Telescope, with star trails smearing the background. Credit: ESO/K. Meech et al., CC BY 4.0 Mission to… somewhere? In 2029, ESA are going to launch a mission to investigate a “dynamically new comet or interstellar object” [15]. The only thing is the mission is yet to have a target. This is because it’s part of ESA’s new fast-class in its Cosmic Vision Programme: a way of intercepting a pristine comet and studying it whilst it’s nearby. Normally lots of planning and preparation is needed to have a space mission, but time is simply not on scientists' side when it comes to fast interstellar and long period comets, taking a short time to whip around the Sun, and taking a very long time to come back again (sometimes never coming back), and by the time they’re back the surface is tarnished and pristine remnants of the early Solar System destroyed [16]. What comets turn into when they are damaged by solar wind and radiation: meteor showers (shooting stars) like this 4 hour exposure of the Leonid meteor shower in 1998 (the remnants of Comet Tempel–Tuttle. Credit: Juraj Tóth/Astronomical and geophysical observatory Comenius University, CC BY-SA 3.0 Such a high risk mission does come with very high reward, and with technology continually improving, we should expect to see and investigate more of these amazing pristine wonders of our Universe, and delve into the history of not just our own Solar System, but that of other planetary systems. by George Abraham, ADAS member. #Comet #Meteor #Asteroid #Borisov #Oumuamua #HaleBopp #OortCloud #Interstellar Click here for the previous news article Click here for the next news article Click here to see where Comet Borisov is in its journey out of the Solar System, here to see where it is in our skies, and here for a video by ESO about the comet. Click here to see where ‘Oumuamua is in its journey out of the Solar System, here to see where it is in our skies and here to watch ESO's video on the discovery of 'Oumuamua. Click here to see where ‘Oumuamua is in its journey out of the Solar System and here to see where it is in our skies (not that it's visible!). Click here to see where Hale-Bopp is in its journey to the Oort Cloud and here to see where it is in our skies. References "What is the Oort Cloud?" BBC Sky at Night Magazine. Archived from the original on 2nd April 2021. "Oort Cloud: The Outer Solar System's Icy Shell". Space.com. Archived from the original on 2nd April 2021. "Kuiper Belt". NASA Solar System Exploration. Archived from the original on 2nd April 2021. "Oort Cloud" Swinburne Cosmos. Archived from the original on 2nd April 2021. "Oort Cloud". NASA Solar System Exploration. Archived from the original on 2nd April 2021. "First interstellar comet may be the most pristine ever found". ESO. Archived from the original on 2nd April 2021. "Comet Hale-Bopp: the story of a visitor from the edge of the Solar System". BBC Sky at Night Magazine. Archived from the original on 2nd April 2021. 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Black Hole Jet Active black holes have many quirks, but none so dramatic than the ‘relativistic jet’. Black holes are well known as the devours of the Universe, but, for the short time that they do this, they don’t just suck particles in; they emit a small number of them in relativistic jets: huge streams of particles travelling at almost the speed of light, which can be millions of light years across and literally punch holes in neighbouring galaxies. In fact, they’re so energetic that they’re thought to be the sources of the fastest particles in the Universe: cosmic rays [1][2]. Discovered in 1912, cosmic rays are made up of protons, electrons and atomic nuclei as heavy as uranium (number 92 on the periodic table) created by relativistic jets, but also by other high energy objects such as supernovae. How do we know this? You might think you could just trace their trajectory back to an origin, but because they interact so much with magnetic fields, that could be wildly different by the time it gets to Earth. Instead, scientists use three methods: Spectroscopy, comparing what light is absorbed and emitted by them and comparing that to other places in the Universe. Weighing the isotopes (varying by number of neutrons) of elements in cosmic rays, since if they’re found in only a few places in the Universe, then it can hint at where the rays came from. Measuring the half-lives (the point where half the isotope has decayed) of radioactive cosmic ray nuclei and how much they’ve decayed, therefore finding out how long they’ve been travelling for [3]. Artist conception of showers of cosmic rays passing through Earth's atmosphere. Credit: Simon Swordy (U. Chicago), NASA Quasars and Blazars However, this phenomenon of cosmic rays doesn’t just have to be seen in our atmosphere: it can also be observed by looking at its source. Quasars are the view we on Earth have of a black hole’s relativistic jets, seen as strong x-ray (high power) and radio wave (low power) sources (along with many other wavelengths of light), whilst blazars are the face on view of a relativistic jet: the view which gives the most amount of radiation, and so the brightest picture, to the observer [4]. But why are they so interesting? Their brightness means they can be seen from long distances (and therefore seen a long time into the past, since light has a speed), but also galaxies between us and the jets can be studied, since the gas in galaxies absorbs some of the light from the jets, leaving ‘absorption lines’ (missing wavelengths of light, characteristic of certain elements). They also exist in galaxies, meaning they’re another way to learn more about the evolution of galaxies. And finally, the origin of their energy source is not yet fully understood [5]. Artist's concept of a blazar using information from the Fermi Gamma-ray Space Telescope Credit: NASA/JPL-Caltech/GSFC The Source In a galaxy far far away resides the wielder of such a lightsaber, only this one isn’t used by something that wants to be a fundamental force (there’s only room for four!): it’s used by M87, or rather M87’s black hole, M87*. In the constellation of Virgo (one of around 2,000 that reside there), and 54 million light-years from Earth [6], M87* is special because it’s active, spewing out high energy particles a whopping 5000 light-years into the voids of space (that must have been some bad meal!) [7]. But how is it doing that? A team of researchers called the ‘Event Horizon Telescope Collaboration’ is trying to answer just that question. Made famous by the image taken in 2019 of the plasma surrounding the event horizon of M87* [8], the team have now taken another image: one which will revolutionise our understanding of the source of relativistic jets. The image is of polarised light coming from the same plasma ring imaged in 2019. But why polarised light? Light, a transverse 'S-shaped' wave, travels in different planes at different angles, so if you filter that light, letting only one plane through, the light becomes polarised, useful in things such as removing the polarised light reflected off rivers, so fishermen can more easily see fish under the water [9]. However, apart from being polarised when reflecting off water, light is polarised when a hot source emits it into strong magnetic fields in space. Therefore, by observing just that polarised light, astronomers are observing just the light which interacts with the black hole’s magnetic field, creating a picture of the magnetic field lines at the edge of a black hole (a bit more high-tech than iron fillings on a bar magnet!) [7]. It took a lot of effort to tease all the polarised light from the immense amount of data they gathered, with between just 10% and 20% of the light being polarised (and some being artificially dimmer due to polarised light travelling in opposite directions and cancelling) [15]. M87* and it's polarised relativistic jet, revealing M87*'s magnetic field. Credit: EHT Collaboration; ALMA (ESO/NAOJ/NRAO), Goddi et al.; VLBA (NRAO), Kravchenko et al.; J. C. Algaba, I. Martí-Vidal, CC BY 4.0 How did they do it? For their data, they used the Event Horizon Telescope: a network of 11 telescopes and telescope arrays from Greenland to the South Pole, and Hawaii to France [10][15], giving a total aperture the size of Earth, linked by atomic clocks to take the data needed at the same time [11]. However, it’s using multiple detectors to create one image, so a technique called ‘interferometry’ is employed. It uses the idea that diffraction gratings (something with many periodic slits of a certain thickness) produce a predictable diffraction pattern (patterns of light and dark lines); only, the telescopes take the place of the slits. These telescopes then observe the ‘Fourier transform’ of the diffraction pattern: a mathematical method of changing a complex signal into a less complex package of sine waves (2D regular 'S-shaped' transverse waves). All this data is then built up over time and put into supercomputers to combine it and produce an image [12]. Researchers then compared the final image with 120 simulations they had created of the black hole’s magnetic field to then find just 15 that fitted: 15 which showed strong magnetic fields diverting matter away from the black hole and into jets [13], whilst resisting any stretching [14]. Two simulated images of M87. Credit: Jason Dexter (left)/Kazunori Akiyama (right), CC BY 4.0 Future for the Project To build a better picture of both the area around the black hole and its magnetic field (seeing a clearer, detailed and less distorted image of the magnetic fields [15]), the team are hoping to also look in different wavelengths of light [14], as well as to take more detailed measurements. Composite X-ray and Radio image of M87 showing blue X-ray producing matter from the Virgo cluster meeting the orange relativistic jets and producing shockwaves Credit: X-ray: NASA/CXC/KIPAC/N. Werner et al Radio: NSF/NRAO/AUI/W. Cotton Hopefully, with many more measurements of not just M87, but other active black holes, we will be able to build a clearer picture of the origin of these most stunning of natural phenomena, and maybe even discover some unexpected facts about black holes along the way. by George Abraham, ADAS member. #BlackHole #Quasar #Blazar #CosmicRay #EHT #Interferometry #M87 #MagneticField #Interference #Diffraction Click here for the previous news article Click here for the next news article Click here to see M87 on ESA Sky (try to pick out its relativistic jets!) Click here to see some helpful infographics about the Event Horizon Telescope explaining all about what they're doing. Click here to watch ESO's detailed video about the imaging of the magnetic fields of M87*. Click here to watch ESO's video showing where M87* is. Click here to watch the simulations of M87 made by members of the Event Horizon Telescope Collaboration. References "Relativistic Jets". NuSTAR. 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A Complex System Jupiter is a gas giant with a big atmosphere. And this atmosphere is mostly hydrogen (the most abundant element in the Universe) at 90%, with the remaining 10% being helium (although there’s a small amount of other molecules like ammonia, sulphur, methane and water vapour in there). However, all this gas doesn’t make one big uniform soup: it makes layers, varying by temperature and pressure, from the troposphere at 50km above the ‘surface’ at -160ºC to -100ºC (creating the characteristic bands of cloud visible from Earth); to the stratosphere at up to 320km high with temperatures similar to the troposphere; to the thermosphere (where the aurora occur) at up to 1,000km high and with hot temperatures of 725ºC. Some may have noticed that the values for the heights are relatively low (in fact, similar to that of Earth’s) and yet Jupiter is a lot bigger than Earth. The reason is that the lower boundary of an atmosphere is defined by having the same atmospheric surface pressure as on Earth (1 bar) [1]. The ‘surface’ in fact extends much much further, but is made of liquified and solidified substances like hydrogen (usually in gaseous form on Earth) because of the intense pressures down there [2]. As well being made of complex layers, the atmosphere is also made of beautifully defined bands. They could be made up of gaseous plumes containing sulphur and phosphorus, moved by the Coriolis effect (the spin of a planet deflecting the direction of wind and water, creating things such as the Gulf Stream on Earth [3]), stronger than on Earth since 1 Jovian day is just 10 hours. This makes extremely fast jet streams separated into light and dark belts [2]; 9 to be exact [4]. And, with little to cause friction because of the absence of a solid surface like on Earth, the winds can get even faster, with some reaching 539km/h at the equator [2]. However, these facts and figures on wind speed could only be calculated because of the clouds in Jupiter’s troposphere, leaving out the stratosphere, until now. The comet Shoemaker-Levy 9 smashed into Jupiter back in 1994 created new molecules which have been carried along by the Jovian winds ever since, and recently studied using the Atacama Large Millimetre/Submillimetre Array (ALMA) at the European Southern Observatory (ESO) in Chile. A team of French astronomers discovered the presence existence of strong jet streams close to the aurorae near Jupiter’s poles, with truly astronomical sizes of 900km in height, 4 times the diameter of Earth and 1,450km/h in wind speed: more than double the maximum in the seemingly measly maximum in the troposphere [15]. Animation of stratospheric winds at the Jovian south pole. Credit: ESO/L. Calçada & NASA/JPL-Caltech/SwRI/MSSS, CC BY 4.0 The Great Red Spot These winds can then create storms, like on Earth, but far far worse, creating a tapestry of colours across the whole of the Jovian atmosphere. There is, however, one that trumps them all: the Great Red Spot. It’s a cyclone-like storm known as an anticyclone (swirling around a high pressure core, as opposed to the low pressure cores found on Earth [7]) that started at least 300 years ago (when it was first observed), whipping up speeds of up to 680km/h (with the threshold for a cyclone being only 119km/h and the fastest surface wind speed on Earth being only 407.5km/h [5]) in an area which could fit 2-3 scale pictures of Earth. “What’s the secret to a long life?” you may ask. Well, on Earth cyclones are generally dissipated by the lack of fuel (water) and friction caused by hitting land. However, this doesn’t happen on Jupiter with no land to cut the fuel of anticyclones [6]. As well as this, another reason has recently been investigated by researchers, in the form of cyclonic cannibalism: the spot sucks up smaller ones around it, visibly making it smaller by chipping away at it, but inflicting the spot with only superficial wounds: much of the 200km deep storm is in fact unaffected. Moreover, the anticyclone rotated quicker after taking a bite from its neighbours, suggesting it was absorbing their energy and maintaining it (even though the anticyclone has been mysteriously shrinking for at least 150 years) [8][9][10]. The Great Red Spot imaged by Voyager 1. Credit: NASA Lights Show But the Jovian atmosphere isn’t all about wind: with the title of the largest continuous structure in the Solar System (apart from the Sun’s vast heliosphere) and at 20,000 times the strength of Earth’s, Jupiter’s magnetosphere stems from its metallic liquid hydrogen outer core that creates a magnetic field when flowing. However, as well as its size, this field is quite different from Earth’s, with two south poles (one near the actual south pole and one near the equator, called the ‘great blue spot’, blue since negative charge is generally denoted by blue) and a confused north pole, where positively charged magnetic field lines don’t have fixed negative counterparts (apart from one section right at the magnetic north pole) [11][12][13]. However, there is one beautiful similarity with Earth in the form of the Jovian aurorae: spectacular iridescent blue rings of fire cover the north and south poles, made of unimaginably high energy electrons, up to 400,000 electron volts (10 to 30 times more energetic than terrestrial aurorae). Moreover, source is different, with Earth’s coming from the solar wind’s interaction with its magnetosphere (magnetic field), whilst Jupiter’s comes from particles escaping its volcanic moon Io which then ionise like solar wind particles on Earth. Recently, another difference between terrestrial and Jovian aurorae was found in the form of a contrast between daytime and nighttime aurorae. Illuminated to by NASA’s Juno spacecraft, the daytime aurorae give out at least 10 times as much energy as its nighttime counterpart: something that couldn’t be seen from Earth since the nightside is never visible [14]. Ultra Violet pole aurorae seen by Juno of Jupiter compared with Earth's. Credit: NASA/JPL Caltech/SwRI/UVS/STScI/MODIS/WIC/IMAGE/ULiège Jupiter still holds many secrets up its sleeve, with much more to learn about its atmosphere and magnetosphere, let alone other equally interesting features it has such as its thin rings and moons, so we’ve got much more to look forward to in the coming years. by George Abraham, ADAS member. #Jupiter #Magnetic #Juno #ESO #ALMA #Aurora #GreatRedSpot Click here for the previous news article Click here for the next news article Click here to watch a video of a simulation by ESO of the stratospheric winds at Jupiter’s poles. Click here to watch a simulation of Jupiter’s magnetosphere, including the peculiar ‘great blue spot’. Click here to see a video by NASA’s Juno team of Jupiter’s cloud belts sped up to show the violent weather system in action. Click here to see the evolution of the aurorae from nighttime to daytime by NASA, JPL-Caltech, SwRI, UVS, and the University of Liège. 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What are Neutrinos? Denoted by the letter “ν” (the Greek letter “nu”), neutrinos are fundamental particles (particles you can’t split up into anything smaller) with a mass of almost zero and a neutral charge. They’re everywhere, with around a thousand trillion of them passing through you every second, and yet they were only discovered in the last century [1]. So, if they’re so insignificant in every way, why does the Universe need them? Well, they’re important in conserving energy in the decay of protons into neutrons and neutrons into protons (called beta plus, β+, and beta minus, β-, decay) [2]. But apart from appeasing the gods of physics, neutrinos help us understand what’s going on in the Sun [3], as well as pinpointing where supernovae are [4]. First Observation of a Neutrino in a hydrogen bubble chamber. Credit: Argonne National Laboratory Opposites But some may have noticed the title includes the word “antineutrino”; not “neutrino”. That’s because the main focus is going to be on the neutrino’s evil twin: the antineutrino. It falls under the umbrella of antimatter: something with the exact same properties as its matter counterpart, except for its charge (plus a few other properties), stemming from how the equations set out by the Bristol born physicist Paul Dirac have two solutions: one positive and one negative, like how the square root of something has both a positive an negative outcome (√4 = +2 and -2). His equation was then interpreted as meaning that for every particle there is a corresponding antiparticle (proton and antiproton, electron and positron, neutrino and antineutrino…) [5]. However, neutrinos don’t have a charge, so what’s different about an antineutrino? Apart from charge, antimatter also changes in spin. All particles (and antiparticles) spin: some clockwise; some anticlockwise. It’s called spin since, if you spin a ball bearing very fast in a magnetic field, it’ll get deflected either up or down (hence the names of the spins are “up” and “down”), depending on which way it’s spinning, and this is how particles act when they’re interacting with a magnetic field (although they’re not actually spinning: in fact the way this works isn’t properly understood). So neutrinos ‘spin’ in the opposite direction to antineutrinos [6]. You may have heard about antimatter and matter in other contexts as well, like how the Universe is made of matter, and yet there was an equal amount of antimatter and matter at the start of the Universe. This is because of something we don’t understand yet, but it’s kept this way by how, if a particle meets the antiparticle version of itself, they annihilate, converting their mass into energy, such as light [5]. And since there’s more matter than antimatter, there’s more than enough matter to annihilate the antimatter whilst having matter which hasn’t been annihilated. First cloud chamber photo of a positron's path. Credit: Carl D. Anderson A Cosmic Source Antineutrinos, and neutrinos, are the bi-product of the weak nuclear force: one of the four fundamental forces in our Universe, responsible for converting protons (positive particles in the nuclei of atoms) into neutrons (neutral particles in the nuclei of atoms) and vice-versa. It allows the components of protons and neutrons, quarks, to change their ‘flavour’ or type, from up to down or vice-versa (with the configuration of ‘ups’ and ‘downs’ determining if the particle is a proton or neutron) [7]. This means that neutrinos and antineutrinos are formed from radioactive processes: processes that change what element something is (for example, hydrogen to helium), found everywhere from supernovae to our own Sun and the Earth below us, showing how active something is [8]. However, they don’t interact much with other particles: lucky since so many go through us every second, but not so for the people who want to observe them. However, they do interact in a way which scientists have now made detectors to exploit. Detectors One key way to detect them is through having a lot of a liquid that’s very pure (i.e. it has nothing else apart from one molecule or element). Apart from being very dangerous (in one experiment, a hammer was hollowed out when it was dropped in the ultra-pure water used), the liquid (e.g. water) interacts with a particle (e.g. electron) which has interacted with a neutrino, giving a flash of light (known as Cherenkov radiation) every time a neutrino hits a molecule of the liquid. This light is then detected by a photomultiplier tube or PTM (a reverse lightbulb, taking in light and converting it into electricity) mapping out where the neutrinos are located [13][9]. However, one experiment, Super-Kamiokande (in Japan), is adding something else to the liquid (water) to make the signal more distinct: gadolinium [9]. At number 64 on the periodic table, gadolinium is a silvery white element used to absorb neutrons in the core of nuclear reactors [10]. However, when it absorbs a neutron, it makes a flash of light. And the same can be said for neutrinos, hitting water enriched with gadolinium: two distinct flashes of light are emitted per interaction with a neutrino, separated by around 30 millionths of a second: a cosmic heartbeat. This distinct signature is then being used by the team in Japan to take out background noise from other interactions to focus on those from neutrinos of a cosmic origin [9]. That said, purity isn’t the be-all and end-all for some experiments, as seen in the experiment ANTARES (Astronomy with a Neutrino Telescope and Abyss environmental RESearch). The experiment is based in the Mediterranean Sea off the coast of Toulon in the south of France [11]. It uses 1,000 photomultiplier tubes over an area of ~0.1km squared, expected to detect less than 100 events per second, seen as minute flashes in the Mediterranean sea water [12]. ANTARES Neutrino Telescope. Credit: François Montanet, CC BY-SA 2.0 FR Both the previous experiments used liquid to find neutrinos, but an experiment based at the south pole became the first detector to go off piste, with a detector observing one cubic kilometre (a gigaton) of ice [13]. IceCube is a detector made up of the IceTop detector (a detector on top of the ice) and the DeepCore detector (a detector 2,500 meters below the ice), working much like liquid based detectors in that it uses photomultiplier tubes (5,160 of them for DeepCore and 324 of them for IceTop), except it uses ice instead of liquid to get the signal [14][15]. Along with IceCube being a terrific feat of engineering, it’s also brought about a few key discoveries, one of which was published in Nature Magazine on 10th March. It is in light (no pun intended) of the recent discovery of a rare interaction of neutrinos that’s called the ‘Glashow Resonance’, theorised in 1959 by theoretical physicist Sheldon Glashow. The theory goes that the ‘virtual’ particle known as a W- boson (a negatively charged particle which mediates the weak force, specifically in β- decay -neutron to proton-, letting the emission of antineutrinos happen) is formed by an electron and an electron antineutrino (a specific type of neutrino) colliding. This event then creates a characteristic shower of high-energy particles (emitting ~6.05 quadrillion electron volts, or ~969 microjoules -it’s a lot of energy when looking at particles!): evidence not only of Glashow resonance, but of it having a source in Outer Space [16][17]. Diagram of the IceCube Neutrino Observatory. Credit: IceCube Collaboration We couldn’t talk about particles without having a bit on CERN, the European Organisation for Nuclear Research (it fits in French!). They’re famous for their Large Hadron Collider (LHC): the world’s largest most powerful particle accelerator [19], but, since it’s antimatter we’re talking about, to observe antimatter, they do the exact opposite. The Antiproton Decelerator (AD) slows down antiprotons to become a beam of antimatter to make antiatoms (atoms made of antimatter) in order to make antimatter (made up of antiatoms), having now made antihydrogen, with ambitions to make many more in the future. This will help scientists study this opposite world and find out what new properties antimatter has, so we can learn more about this less understood corner of particle physics, produced across the Universe [18]. CERN Antiproton Decelerator. Credit: Suaudeu, CC BY-SA 4.0 Why? When neutrinos and antineutrinos interact with the water to produce Cherenkov radiation, a Cherenkov ring is formed. This ring then helps to pinpoint where the neutrino comes from in Outer Space. This then helps scientists get an early alert as to a supernova explosion, for instance, since neutrinos are given out before the main explosion occurs that’s seen from Earth [20]. One such event happened in 1987, where a neutrinos from a supernova explosion in the Large Magellanic Cloud were detected using Japan’s Super Kamiokande [21]. Map of sky with new sources of neutrinos highlighted in circles. Credit: IceCube Collaboration There are also many other uses, from solar physics to atmospheric science, all helping in extending our understanding of this complex Universe. By George Abraham, ADAS member. #Neutrino #Antimatter #CERN #SuperK #IceCube #Supernova #Sun #Atmosphere Click here for the previous news article Click here for the next news article References "What's a Neutrino?". All things Neutrino. Archived from the original on 13th March 2021. "Electron Neutrinos and Antineutrinos". Georgia State University Department of Physics and Astronomy. 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What is an Exoplanet? Exoplanets are bodies like planets, but with one key difference: they don’t go around the Sun; they go around other stars, apart from those known as ‘rogue planets’ which orbit galactic centres instead of stars [1]. First discovered in the 1990s, over 4,000 have been found to date [2], coming in all different shapes and sizes, but categorised into 5 main groups: ‘gas giants’, ‘super-Earths’, ‘Neptune-like’, ‘terrestrial’, and ‘unknown’ (well, nature is always more complex than we’d like it to be) [3]. Gas giants are common in the Solar System, with the planets Jupiter and Saturn falling into this category. They’re large (hence ‘giant’) and mostly made of hydrogen and/or helium (hence ‘gas’) [3], although they do have a solid core, since the pressure and gravity gets so great as to bring about the formation of one (as seen with Jupiter’s core being possibly solid iron in composition) [4]. They also provide some of the best conditions for finding them, with a subcategory of ‘hot Jupiter’ being born from how many gas giants are near their host star, and so, since they’re so massive, they tug on the star and make it wobble (more on that later) [3], leading to as much as 31% of all exoplanets discovered being gas giants (as of now) [2]. Super-Earths are next on the list. More massive than Earth; less massive than ice giants (Neptune and Uranus), but still enormous, at between 3 and 10 times the Earth’s mass, made of a combination of both gas and rock (like on Earth). That said, that’s where similarities with the Earth could stop, since they can be hot enough to vaporise metal, or even covered in a global ocean (I’d stick with this planet if I were you!) [5]. Artist's Impression of 55 Cancri e: a Super-Earth. Credit: ESA/Hubble/M. Kornmesser, CC BY 4.0 Neptune-like is our next category, comprised of, you guessed it, planets with a similar size to Neptune! Often referred to as ice giants (since chemicals like water, ammonia and methane are frozen at the distance Neptune is from the Sun, although these chemicals aren’t frozen closer to a host star or in their interiors), these are exoplanets with often thick clouds of hydrogen, helium, water, ammonia and methane (often something that hides the composition of the atmosphere of these worlds, stopping any light entering to take a spectrum of -more on that later) [6]. Terrestrial is the last type of world I’m going to describe, made up of rock (mainly iron), silicate, carbon and/or water (a category fitting Mercury, Venus, Earth and Mars). These are the ones the tabloid newspapers prick their ears up for the most, since they’re the most Earth-like planets, with the best likelihood of being habitable, yet they’re also the ones with the least number of discoveries (3.1% of all discoveries to date), being the hardest to detect because of their size [7]. TRAPPIST-1 System: Largest collection of habitable terrestrial exoplanets. Credit: NASA/JPL-Caltech Where are they? It’s not something for the average telescope user to look for, but instead entrusts the help of 5 methods of observation and some powerful equipment to locate and categorise them. Methods include: radial velocity, transit, direct imaging, gravitational microlensing and astrometry (no, not astrology!): the ‘Famous Five’ of exoplanet exploration techniques [8]. The radial velocity method, also known as doppler spectroscopy (try saying that quickly!), is the first method employed by people to detect exoplanets. It uses the fact that, when an exoplanet orbits a star, the tug of the exoplanet on the star moves the system’s centre of mass from the centre of the star to somewhere between the two objects (the exoplanet needs to be massive enough to get a measurable effect). This means that the bright star, seen from Earth, appears to wobble back and forth [9]. This wobble is so small that it’s not something that can be seen with the naked eye or even with a large telescope, so doppler-shift was employed: as light moves towards you, it’s squashed (it’s wavelength decreases) making it bluer (blue-shifted); whilst if light moves away, it’s stretched (it’s wavelength increases) making it redder (red-shifted) [10]. Radial Velocity Method. Credit: ESO, CC BY 4.0 The transit method also needs quite a large exoplanet, or for it to be near enough to the star so that, when it travels in front of the star relative to Earth, it periodically decreases the brightness of that star (like a transit of Mercury or Venus in front of the Sun) [9]. It’s also great for finding the diameter of the exoplanet, by studying the difference in brightness from the star’s normal brightness. However, it needs the exoplanet to cover part of the star visible from Earth: something that doesn’t always happen, meaning this method would also miss many exoplanets. Also, there’s that small problem that it’s hard to know if it’s a star passing in front of a brighter star or not [11]. That said, it’s the best method we’ve got, having discovered 3322 planets to date via this method [8]. Direct imaging really does what it says on the tin: you take a picture of an exoplanet. It’s not easy though! Stars can overwhelm the light from exoplanets by over a million times, and the planet must be massive (a few times that of Jupiter), young and far from their host star(s) to have a chance of being observed [9] (detecting just over 1% this way [8]). That said, it’s the most fruitful in data of all the five, showing everything from what the atmosphere is like, to whether there’s water on the surface and if that world is habitable [12]. Gravitational microlensing, our penultimate method, sounds very sci-fi, but it relies on some laws set out in the early 20th century by, you guessed it, Einstein. It uses the fact that, if an object has a large mass, light bends around it (since, famously, mass and energy bend space and time). Again, like the transit method, a perfect alignment is needed [9]. However, if this happens, light from a star with an exoplanet (“star A”) between you and another star (“star B”) amplifies star B’s light. Then, as the light from star B curves around star A, two images of star B are created, making what’s called an Einstein Ring. However, since it’s mass that bends light, the exoplanet also bends some light coming from star B, creating a third image. This creates a second peak of light intensity on top of the main smooth peak: a ‘bump’, characteristic of exoplanets (I hope you got all that!). This means very distant exoplanets (both from us and their host star) can be observed, but they can only be seen once (most likely), since this event is very unlikely to happen [13]. Astrometry is the last in our famous five, using the same premise as the radial velocity method of how a star ‘wobbles’ because of an exoplanet orbiting it . However, instead of using doppler shift to observe it (needing it to move back and forth relative to us), it uses the star’s position in the sky to detect visible, and regular, changes in its position in space: something which needs very precise measurements to yield results [9], leading to only one so far be observed this way: DENIS-P J082303.1-491201b (or VB 10b for short) [14]. Gravitational Microlensing. Credit: NASA/JPL Who’s Looking? There are countless missions and projects looking for them, but here are just a few of my favourites: SuperWASP (no, not from Dr. Who), HARPS, and TESS. SuperWASP (WASP standing for ‘Wide Angle Search for Planets’) consists of two observatories, one in the Roque de los Muchachos Observatory in the Canaries (northern hemisphere) and one in an observatory in south west South Africa near Sutherland (southern hemisphere). It’s a UK run project using robotic camera arrays (8 cameras per telescope) to find exoplanets, employing the lucrative transit method to do this [15]. It has found 174 exoplanets so far [16] including discoveries such as WASP-76b, an exoplanet which rains iron [17], and WASP-107b, an exoplanet with a density of candy floss [18]. SuperWASP cameras, South Africa. Credit: David Anderson, CC BY-SA 3.0 HARPS, or the High Accuracy Radial velocity Planet Searcher (you can see someone wanted it to fit!), is located in the European Southern Observatory’s La Silla Observatory, in the southern Atacama Desert in Chile. It uses the radial velocity method to find its exoplanets, using spectroscopy to see if a star is blue-shifted or red-shifted [19]. And then there’s TESS (no, not from the TV): the Transiting Exoplanet Survey Satellite, using four cameras to detect exoplanets using the transit method. However, unlike the previous two projects, it has the added benefit of a view of the majority of Outer Space, dramatically increasing its probability of success [20] and leading to 120 confirmed exoplanets so far, in just a few years [21]. In fact, TESS (as well as telescopes in Spain, the USA, Chile and Hawaii) has even lead to a recent exoplanet discovery by the CARMENS project consortium (a group of Spanish and German scientists) that have got people listening: Gliese 486b. It’s a super-Earth with a temperature of 430ºC and nearly 3 times a large as Earth. However, it’s interesting mainly because of how its atmosphere expands due to its intense surface temperatures, meaning it’s easier to observe from Earth. Then, with the added benefit of it transiting its host star every 1.5 days, the light from the star can be analysed using spectroscopy to see what makes up the exoplanet’s atmosphere, as well as how they help distribute energy across the planet [22], to see if super-Earths could be stable enough for life to survive [23]. Artist concept of TESS. Credit: NASA These projects could bring up many more candidates for places to observe to find out if they could also harbour life, speeding up our search to find out if our Universe is as devoid of life as it seems. And even if Gliese 486b and others like it don’t turn out to be habitats for life, they could still tell us a lot about the evolution of planets and how our Solar System might have then evolved to become the perfect place for life to start, possibly leading us to the answer of the age old question ‘How did life begin?’. by George Abraham, ADAS member. #Exoplanet #Transit #DopplerShift #SuperWASP #TESS #HARPS #Gliese486b #EinsteinRing #CARMENS Click here for the previous news article Click here for the next news article Click here for NASA's catalogue of exoplanets, and here for the exoplanet encyclopaedia's catalogue. Click here for NASA's orbit simulations for various famous exoplanets Click here to explore artists' impressions of some famous exoplanets References "What is an Exoplanet". NASA, Archived from original on 6th March 2021. "Discovery". NASA. Archived from the original on 6th March 2021. "Gas Giant". NASA. Archived from the original on 6th March 2021. "Inside the Giant". 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