All About Space No. 109의 목차

WELCOME Issue 109 If you could imagine a place where life might exist within our galaxy, where would you think to look? Of course, terrestrial worlds that are a dead ringer for Earth – a so-called Earth 2.0 – could be a haven teeming with organisms, but what about those places submersed in liquid? This month you’ll meet the ocean worlds and discover what secrets they hold. These wet worlds can be found in our very own Solar System, and planetary scientists are shooting straight for them with the next generation of space missions, destined to unlock their true potential to hold life. As Morgan Cable, an astrobiologist at NASA’s Jet Propulsion Laboratory, tells All About Space, the rules of physics and chemistry seem to apply everywhere, but we haven’t…

LAUNCH PAD YOUR FIRST CONTACT WITH THE UNIVERSE New research finds that the Moon is rusty Words by Yasemin Saplakoglu © NASA The Moon is turning ever so slightly red, and it’s likely Earth’s fault. Our planet’s atmosphere may be causing the Moon to rust. Rust, also known as iron oxide, is a reddish compound that forms when iron is exposed to water and oxygen. Rust is the result of a common chemical reaction for nails, gates, the Grand Canyon’s red rocks – and even Mars. The Red Planet is nicknamed after its reddish hue that comes from the rust it acquired long ago when iron on its surface combined with oxygen and water. But not all celestial environments are optimal for rusting, especially our dry, atmosphere-free Moon. “It’s very…

Earth may have been born wet © NASA Earth may not have needed asteroid and comet strikes to fill its oceans. Conventional wisdom has long held that our planet was born dry, because its building blocks formed relatively close to the hot, baking Sun. Earth therefore got the vast majority of its water later, most scientists believe, from impacting objects native to the cold and icy depths of the outer Solar System. Researchers have been arguing for years about whether comets or asteroids were the primary water bearers. Researchers analysed 13 different enstatite chondrite meteorites, a class known to be similar to the space rocks that coalesced to form Earth. They found lots of hydrogen in the supposedly dry meteorites – enough to imply that our planet was born quite…

Ocean worlds SECRETS OF THE OCEAN WORLDS If physics and chemistry are the same throughout the universe, is biology too? Reported by Lee Cavendish © NASA; Tobias Roetsch Earth isn’t the only world which accommodates water. There are moons in the Solar System half the size of Earth that hold much more. These are known as ocean worlds. Astronomers continue to scrutinise these in great detail, as they have the potential to change how biology is viewed throughout the universe. “An ocean world is any planet, or sometimes moon, that has at least ten times the amount of water that Earth does. For reference, Earth is about 0.1 per cent water, so an ocean world has a water content of one per cent or greater,” explains Dr Lynnae Quick, an…

Ocean worlds THE FUTURE OF OCEAN WORLD EXPLORATION These robotic explorers could provide vital evidence to answer astrobiology’s greatest questions 1 EUROPA CLIPPER NASA’s next mission beyond the orbit of Mars is the Europa Clipper, succeeding the Juno mission currently at Jupiter. The mission is scheduled to launch in the mid-2020s. The spacecraft will carry nine scientific instruments, each built for a specific purpose, and will conduct a full scan of the surface. It will also utilise ice-penetrating equipment in order to characterise Europa’s subsurface ocean. © NASA 2 JUICE The European Space Agency has also taken a particular interest in the Galilean moons and looks to visit three of them during its three-and-a-half-year stay. It will arrive at the Jovian system in 2029 and investigate each moon’s…

Star profile: Betelgeuse NEWS FROM BETELGEUSE Mysterious dimming © ESO In October 2019 astronomers began noticing a gradual dimming to Betelgeuse, an effect noticeable even to the naked eye. With the help of Hubble, astronomers have recently concluded that a huge dust cloud appeared between the star and Earth, blocking out a quarter of the star’s surface. By viewing the star using ultraviolet spectroscopy, Hubble mapped a dense, heated cloud of material shifting past the star’s atmosphere in the latter months of 2019. This supposedly formed from super-hot plasma emitted due to an upwelling of a large convection cell on the star’s surface. “With Hubble, we see the material as it left the star’s visible surface and moved out through the atmosphere, before the dust formed that caused the star…

Violent universe ENTER THE COSMIC BATTLEFIELD VIOLENT UNIVERSE The cosmos is not the serene place it first appears… it is full of aggressive offenders Reported by Colin Stuart © ESO As ultraviolet radiation cascades down from space, Earth’s place as a life-friendly planet is under threat. The surface of our world is bathed in this high-energy radiation, and it penetrates our oceans to depths of 75 metres (246 feet). The damage is catastrophic. The intense glare fries ocean plankton, and those organisms which survive divert all their energy to repairing their DNA rather than photosynthesising. Oxygen levels then drop as carbon dioxide levels rise. The knockout blow for many larger species comes as dwindling plankton numbers offer scant food resources, with the effect rocketing up the food chain. Thankfully…

HOW TO TAKE AWARD-WINNING ASTROIMAGES Astrophotography used to be just for the experts, but not any more BY THE WINNERS OF INSIGHT ASTRONOMY PHOTOGRAPHER OF THE YEAR © Mark Gee Like the fields and rolling green hills of the countryside on a summer’s day, or the ocean bathed in a golden sunset, a starry night sky is so beautiful that it’s only natural that people want to photograph it. Similar to any creative hobby, there are different levels of expertise you can aspire to and reach. From dark-sky sites, often far from their homes, experienced astrophotographers use high-tech cameras attached to expensive telescopes to capture multiple images of deep-sky objects, which they then layer – or ‘stack’ – together and process using sophisticated image-processing software to create portraits of…

The Andromeda Galaxy’s halo is more massive than initially thought © NASA/ESA Galactic halos are both more massive and more complicated than scientists realised, according to new Hubble observations. The venerable telescope turned its sights on the neighbouring Andromeda Galaxy using dozens of different quasars to map the galactic halo. Andromeda, more formally known as Messier 31, is a spiral-shaped galaxy about the same size of the Milky Way we live in, with about 1 trillion stars. Cosmically it’s right next door, just 2.5 million light years away, which means that Hubble can study its halo in unprecedented detail. “This is truly a unique experiment because only with Andromeda do we have information on its halo along not only one or two sightlines, but over 40,” said Nicolas Lehner, an…

Scientists spot a triple star system shredding its planet-forming disc © ESO Groups of stars can tear their planet-forming disc to shreds, leaving behind warped, misaligned rings. Solar systems like ours generally form with their planets all orbiting in the same flat plane – but this isn’t always the case. After 11 years studying GW Orionis, a young triple star system lying 1,300 light years away with a circumstellar disc, a team of researchers found the first direct evidence that groups of stars can actually tear apart their discs. This work reveals a disc that isn’t flat at all, and is instead misaligned and broken. “There have been a number of theoretical studies on disc-tearing effects, but this is the first direct evidence of the effect occurring in a planet-forming…

DYSON SPHERE Could an advanced civilisation harness the power of stars to sustain their energy needs? © Jay Wong First proposed by physicist Freeman Dyson in 1960, a Dyson sphere is a hypothetical swarm of satellites that would surround a star in order to harness its energy. Although more commonly known as a Dyson swarm, some people have discussed the possibility that rather than a swarm of satellites, a star could be encased in a solid sphere by a future civilisation – but this is an idea that Dyson himself was keen to stray away from. Indeed, for a planetary system like our own, such a structure would likely require every object in the Solar System other than the Sun to be dismantled and rebuilt into a giant sphere owing…

Focus on EXTINCTION BY SUPERNOVA Earth’s fossil record suggests its ozone layer took a protracted beating © Tobias Roetsch One of the worst extinction events in Earth’s history may have been triggered by a supernova, the violent death of a distant star. About 75 per cent of all species on Earth died out at the end of the Devonian Period, nearly 360 million years ago. Rocks from this era preserve many thousands of spores that appear to be scorched by ultraviolet (UV) radiation, indicating that something went seriously wrong with our protective ozone layer. The destructive force may have come from very far afield. “Earth-based catastrophes such as large-scale volcanism and global warming can destroy the ozone layer too, but evidence for those is inconclusive for the time interval in…

MAKING OUR SUN’S DARKER COUSIN Formed not long after the Big Bang, these brilliant members of the early universe aren’t your conventional stars © Tobias Roetsch THE EARLY UNIVERSE After the birth of the cosmos some 13.8 billion years ago, the universe expanded. Within less than a second, temperatures rose extremely high, and a soup of particles made up the observable cosmos that we see today. Some 70,000 years after the Big Bang, dark matter supposedly dominates. THE FIRST ‘STARS’ It’s thought that dark stars began with a mass similar to our Sun. Eventually they grew to millions of times its mass, before the true first stars burst into existence. They would have been surrounded by enormous clouds of hydrogen and helium, hundreds of thousands of kilometres across. DARK MATTER…

KEEPING VIGIL OVER VIOLENCE © Adrian Mann 1 Spotting the burst The Neil Gehrels Swift Observatory views half of the sky every time it orbits Earth, and its Burst Alert Telescope (BAT) is always on the lookout for sudden, intense flashes. When it spots one, it immediately sends a message to astronomers on Earth and automatically orientates itself for a closer look. 2 Studying it further The Ultraviolet/Optical Telescope (UVOT) on board the satellite is also pointing in the same direction as the X-ray Telescope (XRT). It can pick up some of the other forms of light created during the GRB. 3 Pinning it down Within a minute of BAT being triggered, Swift’s X-ray Telescope will have worked out the precise location of the gamma-ray burst to…

STARGAZER ESSENTIAL GUIDES AND ADVICE FOR AMATEUR ASTRONOMERS What’s in the sky? Jargon buster Conjunction A conjunction is an alignment of objects at the same celestial longitude. The conjunction of the Moon and the planets is determined with reference to the Sun. A planet is in conjunction with the Sun when it and Earth are aligned on opposite sides of the Sun. Right Ascension (RA) Right Ascension is to the sky what longitude is to the surface of the Earth, corresponding to east and west directions. It is measured in hours, minutes and seconds since, as the Earth rotates on its axis, we see different parts of the sky throughout the night. Declination (Dec) This tells you how high an object will rise in the sky. Like Earth’s latitude, Dec…

Moon tour Copernicus This month we bow down before the ‘Monarch of The Moon’ © NASA Ask any Moon observer to name their favourite lunar crater and chances are most will nominate the same feature: Copernicus. Copernicus has a nickname – the Monarch of the Moon – and if you’ve only ever seen photographs of the crater but never seen it with your own eyes, you would be forgiven for thinking that sounds a bit pompous. But it is entirely justified. Just as every amateur astronomer remembers their first view of Saturn and its rings through a telescope, or their first display of the northern lights, they never forget the first time they see Copernicus through a telescope. In fact, the crater is one of the first things a beginner…

LAUNCH PAD YOUR FIRST CONTACT WITH THE UNIVERSE © ESA © NASA/ESA & Hubble Meet the Meathook Galaxy The long-serving Hubble Space Telescope continued to capture stunning sights of the universe throughout August and September. One fruit of its imaging surveys is this spectacular close-up of NGC 2442, also known as the Meathook Galaxy. The structure gets its nickname thanks to its asymmetrical and irregular shape. In March 2015, the Meathook captured the attention of astronomers when one of its white dwarf stars exploded as a supernova, creating an eruption of light so dazzling it was visible from Earth for several months. Spitzer sees a star factory in infrared NASA’s recently retired Spitzer Space Telescope was capable of revealing aspects of space invisible to the human eye. It was fixated…

Same black hole can collide with its kin multiple times, lopsided merger suggests Words by Meghan Bartels © NASA/JPL-Caltech For black holes, a collision doesn’t have to be a once-in-a-lifetime experience. On 12 April 2019, scientists detected a new black hole merger using a trio of gravitational-wave detectors. Astrophysicists have spotted such events before, but something about the signals was different: the two black holes that collided were incredibly unevenly matched, with the larger about three times the size of the smaller. “This event is an oddball the universe has thrown at us – it was something we didn’t see coming,” said Salvatore Vitale, a physicist at the Massachusetts Institute of Technology. “But nothing happens just once in the universe. And something like this, though rare, we will see again,…

DARK STARS These cosmic creators, powered by dark matter, could be responsible for our existence, along with the appearance of today’s universe Reported by Amanda Doyle © Tobias Roetsch A star dies. A sudden flash of light signifies the end in a supernova explosion. This, however, is only part of the life cycle of stars, as the rich materials created during the death throes of the star are ejected into space by the supernova. When the next generation of stars form, they sweep up the leftovers of the supernova, accreting the metals that the dying star produced – metals being the term that astronomers use for anything heavier than hydrogen and helium. Metals are important; without them, the disc of gas and dust surrounding a newly forming star could not…

AT THE HEART OF A MONSTROUS MAGNET © Tobias Roetsch 1 Magnetic field Magnetars are known for their extremely powerful magnetic fields, which produce high-energy X-ray and gamma-ray bursts. These magnetic fields are hundreds of millions times stronger than any human-made magnet on Earth. 2 Outburst The fireball, produced by magnetic field decay, ejects intense flashes of high-energy electromagnetic radiation. These giant flares leave the surface of the magnetar at the speed of light, and their radiation has even been recorded on Earth. 3 Solid crust This outer layer is often only 500 metres (1,640 feet) thick. Eventually it fractures under the extreme magnetic stress. After all, a magnetar placed at the distance of the Moon could wipe all the credit cards on Earth. X-rays are then…

STARGAZER This month’s planets Mars hits opposition with far-flung ice giant Uranus, while Jupiter fades as we roll into November Planet of the month For the first time since 2018, the Red Planet, Mars, reaches opposition, gracing our skies as a shining red orb from dusk until dawn. Other than Venus and the Moon, Mars will be the brightest object in the night sky. It’s also handily placed, reaching about 45 degrees above the horizon at 02:00 on opposition night of 13 October. Every time Mars is at opposition, an email hoax does the rounds claiming that Mars will appear as large as the full Moon in the sky. This is not true - you won’t even be able to make out the disc shape of Mars with the unaided…

STARGAZER Vixen A70Lf with Mini Porta mount An extremely affordable starter package that’s easy to use and a breeze to set up Vixen has kept the novice astronomer in mind, making the A70Lf a very portable ‘grab-and-go’ telescope that’s no trouble transporting for a night of observations. The overall build of the A70Lf is of good quality for the price, with very good quality cast rings and a versatile Vixen dovetail, allowing you to fit the telescope tube to a variety of compatible mounts. The tripod legs of the Mini Porta mount are perhaps a bit too light, but seem to hold the tube steadily enough for observing, provided you have positioned the telescope on a level surface and treat the entire set-up with care. Due to its small aperture…