Indholdsfortegnelse for January - February 2021 i Australian Sky & Telescope

AN INTERNATIONAL TEAM of researchers, led by Jane Greaves (Cardiff University, UK), has announced the detection of phosphine — a gas potentially associated with life — in the relatively cool cloud decks of Venus. Astronomers have previously found phosphine surfacing from the depths of Jupiter and Saturn, where the high-pressure, hydrogen-rich, and intensely hot environments provide the right conditions to make the molecule. But anaerobic microbes produce it in less extreme places on Earth, too. Greaves and her colleagues observed Venus first in 2017, with the James Clerk Maxwell Telescope (JCMT), then again with the Atacama Large Millimeter/submillimeter Array (ALMA) in 2019. They found a chemical fingerprint of phosphine at a wavelength of 1.123 millimetres, at which the molecule absorbs thermal radiation coming from clouds lower in the planet’s atmosphere.…

WE MAY FINALLY HAVE FOUND the missing source of most of Earth’s water in a rare class of meteorites called enstatite chondrites. These rocks come from the part of the protoplanetary disk in which the terrestrial planets formed. While the meteorites’ composition resembles Earth’s, astronomers had presumed them too dry to supply water. But a new analysis including the most pristine samples known shows that the original population could have supplied more than enough water to fill our oceans, Laurette Piani (University of Lorraine, France) and colleagues report in the journal Science. Astronomers think Earth and the other terrestrial planets formed too close to the young Sun for water to condense. While water could have condensed out near Jupiter, beyond the snow line of the young Solar System, it would…

December 2020 14 The Geminids, a mostly northern meteor shower, will peak this morning. With New Moon on the 15th the skies will be clear of moonlight interference. 21 Solstice. Today the hours of daylight are longest in the Southern Hemisphere, and the Sun is furthest south in the sky. 21 Jupiter and Saturn are only 0.1° apart. This’ll be a spectacular sight to the naked eye, but even more amazing through binoculars or a telescope. January 2 The Earth is at perihelion today, it’s closest point to the Sun. The distance will be 147,093,154 km, or 0.983257 astronomical units. 12 Venus and the thin crescent Moon will appear close together. 21 Mars and the Moon will be 4° apart. Take a look through binoculars and you should be able…

TORCHES (OR FLASHLIGHTS AS THEY SAY IN THE U.S.) help us find our way through pitch-black bushland or a house that’s just lost power. But researchers want to use a torch in another way: to find and characterise water ice in one of the darkest, coldest places in the solar system — the Moon. Astronomers already know that patches of ice exist on the lunar surface at both the north and south poles. Hidden from direct sunlight and thus extremely cold, these regions are where ice delivered by comet impacts and other processes can gradually accumulate and survive on geologic time scales. The distribution of water ice in these cold traps varies between the poles, from place to place, and even within a single deposit. But scientists know little about…

Photographing geostationary satellites is pretty easy for a couple of reasons. First, there are so many that it’s almost guaranteed there will be several available at any time of night. Second, they’re found along a narrow path near the celestial equator. You can photograph a geostationary satellite with any camera capable of taking exposures of several seconds or longer, and a regular tripod. Just about any lens will do, though you’ll see individual satellites more clearly if you use a telephoto lens with a focal length of 100 mm or more. Set the lens to f/4 and the camera ISO to 1600, then focus your camera on a star. Next, aim at the correct declination for your latitude (see the table on the next page) and open the shutter for…

Roughly 100 years ago, Harvard College Observatory astronomer William Henry Pickering proposed that vast swarms of insects move across the lunar surface. It was a fantastical attempt to account for the Moon’s changing brightness as the Sun’s elevation changes throughout the lunar day. He was wrong, but now modern astronomers, using the highest quality orbital data, have detected ‘ANTS’ on the Moon. ANTS is an acronym for active nearside tectonic system, a phrase describing evidence for extensive small-scale movement of areas of the Moon’s surface. In a paper published earlier this year, Bern University graduate student Adomas Valantinas and Peter Schultz of Brown University focused on more than 500 locations where clusters of fresh, metre-sized boulders are exposed along the tops of mare wrinkle ridges. While visible in high-resolution Lunar…

NASA’S KEPLER TELESCOPE was retired a few years ago, but ongoing analyses of its data, both by professional astronomers and citizen scientists, are still producing new results. The mission’s primary goal was to try to estimate the prevalence of Earth-size planets on Earth-like orbits around Sun-like stars. But understanding the occurrence of such planets has proven difficult, even though Kepler has found more than 2,600 exoplanets (and counting). Now, an international collaboration led by Steve Bryson, a researcher at NASA Ames, has announced a refined estimate. The team, including NASA scientists, SETI researchers, academics, former-Keplerites and other planet hunters, performed a statistical analysis that combined Kepler’s planet catalogue and stellar data from the European Space Agency’s Gaia observatory. They found that about half of the Sun-like stars in our galaxy…

Permanently dark craters are no longer the only places to find water on the Moon. NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) has found evidence of water molecules in the Moon’s sunlit Southern Highlands. A separate analysis of lunar topography found that areas as small as a centimetre across — but totalling up to 8,000 square kilometres — could act as cold traps where water ice collects. Spacecraft observations have revealed the presence of water ice in permanently shadowed craters at the lunar poles, where temperatures stand below the –163°C vacuum sublimation point of water ice. Other studies have also found that the spectral fingerprints of hydrogen at near-infrared wavelengths of 2.8 to 3 microns are widespread on the sunlit part of the Moon. However, while those features can come…

One of the few good things about 2020 was the relatively large number of comets that became bright enough to be viewed with small telescopes. Even though the Southern Hemisphere missed out on the best part of the Comet NEOWISE show, we still had the opportunity to study several interesting comets. The year will end, however, on a less auspicious note with the best prospect being the fading P/2020 M3 (ATLAS). This large and diffuse object reached maximum brightness in October and November but, because of its large and very diffuse appearance, was given a wide range of brightness and size estimates by observers using different instruments and observing from sites of differing sky quality. Typical of such comets, the brightest estimates (close to magnitude 7) were made using binoculars…

WITH THE ARRIVAL OF THE SUMMER MONTHS, I make sure I don’t waste a minute of the easy viewing, great weather and endless array of sights to see in the sky. And even though there are plenty of faint fuzzies available for study, I also often like to take the time to enjoy some of the biggest, boldest, brightest and most beautiful targets I can find. Here are some of those glorious targets guaranteed not to waste your time. First off, of course, is M42, the famous Orion Nebula. If you had to choose only at one item to look at in the summer sky, this would be it. The middle of the sword hanging from Orion’s belt, this emission nebula is arguably the best in the sky (although some…

Scientists have reported phosphine, a candidate biosignature gas, on Venus! Exciting, but what does it actually mean? There are three possible outcomes. Least likely is that it turns out to be genuine evidence for life, but we can’t rule this out and indeed must take it seriously as a viable hypothesis while we investigate further. That’s worthy of excitement and wonder. Barring life, phosphine may point to unknown chemistry in the Venusian atmosphere. This is important to understand if we hope to use biosignature gases to infer the possible presence of life on exoplanets. Or, the detection could be shown to be false, as scientists scrutinise, repeat and supplement the detection methods with further, less ambiguous techniques. The team that published this finding did careful, rigorous work, but it was…

The winners of the Auckland Astronomical Society’s annual national astrophotography competition have been chosen, with the announcement made at the Society’s annual gala Burbidge Dinner on November 7. You can see a slideshow of the images at https://youtu.be/_7y_ IKmisT0. The Auckland Astronomical Society (astronomy.org.nz) is New Zealand’s largest, with more than 600 members. It was founded in 1923 and is based at the Stardome Observatory and Planetarium near Auckland’s famous Maungakiekie/One Tree Hill. The call for entries for the annual WA Astrophotography Competition has now gone out, and there are some serious prizes up for grabs, including a Sony Alpha 7 MkIII and 24F14GM wide angle lens, together valued at $6,399 and provided by prime sponsor, Sony Australia. The winners will be announced at the Perth Astrofest in February 2021,…

Dad isn’t with us anymore but there’s a picture of him on my lounge room wall that must have been taken around the time that he and I were building my first telescope. To be honest, I wasn’t impressed with the way that he had pushed me aside and gotten on with the job himself; I was sure I had made a good start. The frame was sure to stay together eventually. Perhaps it needed longer nails, or maybe shorter nails, or glue. You see, I had to come up with something to beat Charlie Weeks. He was older than I was, already 12 and a real know-it-all. He assured me that he was well underway building a 15-cm Newtonian reflector in his backyard. Charlie had indeed made a good…

EARLIER THIS YEAR, FURORE surrounded Betelgeuse — the star had ‘fainted,’ dimming more than expected in its usual cycle of brightness changes, leading some to suggest the star might go supernova sometime soon. But even as astronomers begin to get a handle on the red giant’s unexpected behaviour, they’re still struggling to understand its basic properties — namely its size and distance. Meridith Joyce (Australian National University) and colleagues reported that Betelgeuse is actually smaller, and therefore closer, than previously thought. Not everyone agrees with the results. Nevertheless, the study represents a new — and needed — approach toward understanding this enigmatic giant. As a red giant star, Betelgeuse isn’t quite stable. It has run out of hydrogen to fuse in its core and is relying on helium fusion to…

ASTRONOMERS STUDYING IMAGES of massive galaxy clusters have uncovered a potential problem with dark matter. In the journal Science, Massimo Meneghetti (National Institute of Astrophysics, Italy) and colleagues report a new way of visualising unseen dark matter in galaxy clusters — and their results contradict cosmological expectations. Theorists have long known that dark matter isn’t smooth. Instead, like a botched baking project, the dark matter halos that surround galaxies and clusters have lumps, or as astronomers term them, subhalos. Simulations specify how many subhalos we might expect around the galaxies in a cluster. Some of them could have stars and be faintly visible as dwarf galaxies, while others might be entirely dark. In any case, most of them would be difficult to observe. Meneghetti’s team came up with a way…

You’ve probably heard the expression “the dog days of summer” and understood it to refer to unusually hot weather, but you might not be aware that it’s rooted in Northern Hemisphere astronomy. The brightest star in the night sky is Sirius, in the constellation Canis Major — the Great Dog. If you turn to our sky map on page 42, you’ll find Sirius plotted near the centre edge of the chart. So how does a star that’s prominent in the Southern Hemisphere summer become associated with long, sultry summer days in the northern half of the planet? If you’re an early riser, you can spot Sirius (the “Dog Star”) in early August, glinting in the morning twilight at the time of year that’s often hottest in the Northern Hemisphere —…

WHEN Early December 1 am Late December Midnight Early January 11 pm Late January 10 pm These are daylight saving times. Subtract one hour if daylight saving is not applicable. HOW Go outside within an hour or so of a time listed above. Hold the map out in front of you and turn it around so the label for the direction you’re facing (such as west or northeast) is right-side up. The curved edge represents the horizon, and the stars above it on the map now match the stars in front of you in the sky. The centre of the map is the zenith, the point in the sky directly overhead. FOR EXAMPLE Turn the map around so the label “Facing NE” is right-side up. About halfway from there to…

VY Canis Majoris is a red supergiant irregular variable star that is attracting professional research interest for the amount of mass it is losing. Multi-wavelength images of its envelope and surrounds suggest that it has been losing an average of 0.0006 of a solar mass per year for last 1,200 years or more, including episodes of anything up to 0.01 solar mass. In other words, we might be seeing chunks of the star being ejected. How this mass loss proceeds will determine VY CMa’s next evolutionary stage: red supergiant turned supernova, a hotter star or a black hole. Our starting point for star-hopping to VY CMa is Wezen (δ CMa), not far to the south of Sirius (α CMa) and plotted on both the all-sky chart in this issue and…

PHOTOGRAPHING THE MOON and planets has long been a mainstay of both amateur and professional astronomy. Using high-speed digital video cameras and innovative processing techniques, amateurs today regularly produce pictures of our neighbouring worlds that resolve tiny details only fleetingly glimpsed in the eyepiece. Taking high-resolution photos of delicate clouds in the atmosphere of Mars, interacting storms in the belts of Jupiter or the polar hexagon on Saturn is well within the grasp of anyone with patience and a relatively modest telescope. Here’s what you need to get started. Choosing your tools The resolution of your planetary images will be dependent on the telescope you use. Almost any instrument can produce excellent planetary images. But to record the smallest swirls in Jupiter’s cloudtops or changes in the receding polar cap…

LET’S BE HONEST: To the untrained eye, most celestial objects look unimpressive through a typical backyard telescope. Sure, there are exceptions, such as the Moon, bright planets, the (safely filtered) Sun; the most colourful double stars; and about as many showpiece star clusters, nebulae and galaxies as you can count on your fingers and, if you’re generous, your toes. But most of the deep sky objects in celestial atlases and catalogues are not worth showing to our non-astronomer friends and neighbours, because the dim grey views through the eyepiece just can’t compare with the bright colourful Hubble images the public has become used to seeing. Unistellar, a crowd-funded startup with offices in Marseille and San Francisco, has come up with a solution: the eVscope, or ‘enhanced vision’ telescope. Advertised as…

Rick Stevenson is a Brisbane-based astrophotographer who, like many others, got into astronomy as a child and then lost interest for a while before returning to the hobby. Having been through the end of the film era, he now images the sky with a variety of CCD and CMOS cameras. What got you into astronomy? I was interested in the sciences from an early age, poring over books and magazines. When I was around 11 years old, we went to Sydney on holidays and did the rounds of the bookstores. In one of them I found a folded ‘map’ of the night sky. I had no idea how to use it but soon managed to identify many of the bright southern stars and constellations. What was your first telescope set-up?…