Innholdsfortegnelse for May - June 2021 i Australian Sky & Telescope

A DISTANT SUPERMASSIVE black hole is flaring in a surprisingly regular pattern, and astronomers think it betrays the piecemeal devouring of a star. On November 14, 2014, the All-Sky Automated Survey for Supernovae (ASAS-SN), a global network of 14-cm robotic telescopes, detected a flare in the core of a misshapen galaxy 570 million light-years away. Astronomers initially thought the flare, catalogued as ASASSN-14ko, was a supernova, or maybe the temporary brightening of a supermassive black hole. However, when Anna Payne (University of Hawai‘i, M noa) went back over six years’ worth of data, she found similar flare-ups occur every 114 days. Payne and colleagues observed the days-long flashes with various facilities, including four large amateur telescopes in Australia, South Africa and Brazil and several X-ray satellites. Payne discussed the analysis…

THE PERTH ASTROFEST Astrophotography Competition, held each year, attracts some of the best sky imagery to be found anywhere on Earth. On these pages we’re pleased to present just a small selection of the winning and runner-up images — you can see more of them, plus some video entries, at astronomywa.net.au.…

Every genre has its tropes, and science fiction is no exception. Stories set in space often centre around the discovery of strange new worlds, and the narrative tradition in these situations usually demands that someone ‘scan for signs of life’. It’s quite simple, really: An order is given, a touchscreen touched and an answer promptly received. If you’ve ever wondered at this fictive sleight-of-hand, and whether such remote sensing is even possible, you’re in good company. Astrobiologists all across the world are laboring to transform this pretend practice into a real science. We are a long way from, “Alexa, check for life signs on Kepler-186f”. But someday, we may know enough about the clues life creates to estimate what portion of our galaxy’s terrestrial worlds, if any, are life-bearing. The…

Finally. After a series of penumbral eclipses, on May 26 we’ill enjoy the first total lunar eclipse in long time. But this will be a short and sweet event. When the Moon passes directly through the centre of Earth’s umbral shadow, totality can last up to 1¾ hours. However, during May’s eclipse the Moon will barely edge inside the umbra, spending only 18.4 minutes there before coasting back into the much lighter penumbra. The fraction of the lunar disk immersed in the umbra is described by the magnitude of the eclipse — the greater the magnitude, the longer the eclipse. A total eclipse has a magnitude of 1 or greater, and a deep eclipse — when the Moon passes through the centre of Earth’s shadow — has a magnitude around…

AMATEUR ASTRONOMER Milton Antonick got his start with a traditional 20-cm Dobsonian, then graduated to a 15-cm Maksutov-Newtonian, which he used to complete a three-year study of the Messier objects. But the latter scopes takes up to an hour to thermally stabilise and is difficult to collimate. Milt wanted a scope that had minimum set-up time, minimum cool-down time and no need to collimate in the field. The latter suggested a refractor, and after viewing through several of them he decided to build one. He wasn’t quite up to grinding his own lenses, so he bought a 15-cm lens set, but the rest is all his own. Milt sketched out the scope body using Alias software tools, determining the scope’s dimensions, baffle placement, focuser, drawtube length etc. He did the…

IN 1977, THE BIG EAR radio telescope at Ohio State University recorded the so-called Wow signal. It was the best candidate for an interstellar radio signal found during the university’s seven-year search for extraterrestrial intelligence (ETI). It’s also one of the best ever reported and the most well known. In the more than four decades since, I’ve searched for the Wow signal a half-dozen times, because detecting it a second time might mean the discovery of ETI. I’m not a professional astronomer, but I know enough about radio telescopes to use them in searches for ETI, and I usually collaborate with a trained astronomer. Gerry Harp, some of his colleagues at the SETI Institute and I recently had the longest listen ever for the Wow signal — 100 hours using…

THE EXISTENCE OF A QUASAR in the infant universe is helping astronomers understand black hole formation. Feige Wang (University of Arizona) and colleagues report the detection of a 1.6 billion-solar-mass black hole just 670 million years after the Big Bang (at a redshift of 7.64), around the era when the first stars were beginning to shine. The discovery leaves astronomers wondering, how did the mass of more than a billion Suns come together into a black hole so early on? One school thinks that black holes come from massive stars. The very first generation of stars — known as Population III stars — would have fit the bill: They had on the order of hundreds of solar masses, burned fast and died young. The other school of thought skips stars…

ASTRONOMERS USING the Transiting Exoplanet Survey Satellite have discovered three planets orbiting a star about 10 billion years old — one of them rocky. The star, TOI 561, resides in our galaxy’s older and fatter thick disk, so its planets have a nice view of the Milky Way’s spiral from on high. The planets have diameters 1.45, 2.9 and 2.3 times Earth’s, respectively. The innermost one is a rocky planet, whose average density is similar to our own. But it’s on an orbital period of 0.44 day, and it’s anything but Earth-like. The dayside surface temperature is around 2,200°C. That’s at least twice as hot as Earth’s magma, and it’s surely molten. What it actually looks like is uncertain because, as lead scientist Lauren Weiss (University of Hawai‘i, M noa)…

AFTER AN AMAZING, pinpoint skyhook landing on February 18, NASA’s Perseverance rover is starting to flex its nuclear-fuelled, mechanical “muscles” as it prepares to explore its new home in Jezero Crater on Mars. NASA held a press conference on March 5 listing the accomplishments of Perseverance thus far and giving us a preview for what’s next. The one-tonne rover rotated its wheels and performed a 6.5-metre roll-and-turn drive, using the hazard avoidance cameras to snap images of the tyre tracks. Commissioning also continued for on-board instruments, including test movement for the mechanical arm on Sol 12. (Sol is the word for a Martian day.) Wind sensors on the main mast were also deployed. “Perseverance has been doing an exceptional job during the first two weeks on the Red Planet,” says…

BRING UP THE TOPIC OF EYEPIECES with a group of seasoned observers and you better be prepared for a cascade of opinions. Comments about eyepiece designs, brands and even costs are likely to surface along with opinions about such fundamentals as what range of magnifications is important for various types of observing. So, it’s not surprising that eyepieces can be a confusing subject for someone new to the hobby of astronomical observing, especially given the huge variety of eyepieces available in today’s marketplace. It’s been a while since we’ve run a general article on eyepieces, so what follows is a bit of an eyepiece primer mixed with some thoughts on how the conventional eyepiece wisdom I learned entering the hobby many decades ago has changed over the years. Everyone knows…

There are two bright stars visible in our northern skies that are only 4½° apart and so similarly bright that they have attracted much attention throughout history. Their location in the zodiacal constellation Gemini further helps their recognition since they’re near enough to the ecliptic that the Moon passes by fairly closely each month, and once in a while so does a planet. Naturally, this pair of almost-twin stars are named after one of the most famous pair of twins in history: the mythological brothers Castor and Pollux. Let’s take a look at them before they disappear from our mid-year skies. Compare and contrast Pollux and Castor. Stargazers often refer to the twosome as Pollux and Castor because Pollux is slightly brighter, but in mythology the tradition is to reverse…

There is a small group of long-period variable stars that have the most unusual light curves. Rather than having regular optical minima and maxima, they show a dual maximum. TT Centauri is one such star; there are only five or six other dual-max stars out of the hundreds of known LPVs. Classification of LPV light curves is problematic; suffice to say these dual-max stars are rare. As a group they have long periods, 400 days or more, and complex, unstable, pulsating gaseous envelopes enriched by the convective dredge-up of heavy elements from within the star. TT Cen is the subject of ongoing observing campaigns run by the Variable Stars South (VSS, variablestarssouth.org) and the American Association of Variable Star Observers (AAVSO, aavso.org) organisations. Other dual-max stars R Normae, BH Crucis,…

Even though the COVID-19 pandemic situation has become much better across Australasia, things are still very up in the air with regard to most of the regular annual star parties and astrofests. It’s hard at the moment, of course, for organisers to plan too far ahead. Let’s hope that the vaccine roll-out and other measures will enable all of us to return to normality very soon, so that more face-to-face events can be held again. That’s not to say that all events or activities have ceased. A new astronomical festival has been arranged to take place under what could be argued as being some of the best skies in the world. The Dark Skies Festival will be held near Alice Springs from May 6 to 14, 2021, with local tourism…

NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) has captured a new view of the Whirlpool Galaxy (M51), 31 million light-years away in Canes Venatici. By imaging polarised light, SOFIA’s High-Resolution Airborne Wideband Camera mapped out M51’s magnetic field. The resulting magnetic streamlines are shown overlaid on the image at right. While radio observations had revealed that the magnetic field lines trace the spiral structure in the inner parts of the galaxy, the SOFIA data show for the first time that the field lines in the outer arms do not follow the same order. Intense star formation in these outer regions may be causing magnetic chaos, and the gravitational tug of neighbouring galaxy NGC 5195 probably also plays a role.…

This is my 60th Binocular Highlight column. I’ve had this gig for five years now, which is hard to believe. When I first started here, I made a little deal with myself to stay away from the Messier objects as much as possible. I figured that would push me to go find new stuff — and it did! It’s been one of the best things about writing this column: I have a professional responsibility to go out often, and to be omnivorous in my observing. Still, a Messier every now and then is no catastrophe. One of my favourites is M48, an open star cluster in the constellation Hydra, the Water Snake. It’s a truly breathtaking sight, sprawling across almost a full degree. The cluster is chock-full of stars, but…

The end of February brought some exciting news concerning the discovery of a comet found in images taken by the SWAN instrument aboard the SOHO Sun-monitoring spacecraft. The discovery was made by Michael Mattiazzo of Swan Hill in Victoria; this is the 9th SOHO discovery he has now racked up. Congratulations to Michael for making this difficult discovery. The first images were found on February 25, but they were so vague that nobody was confident that the object was real until a confirming image was obtained by Michael Jager on February 28, when the comet appeared low in the evening twilight. The comet was then located by several Northern Hemisphere observers at the end of February and the beginning of March, with a brightness estimated to be about magnitude 10…

Tycho and Copernicus are frequently presented as archetypal lunar craters, and they are indeed beautiful and fresh. But most lunar craters aren’t fresh. Many are much older and have been modified by subsequent events, including shaking from moonquakes and showers of ejecta from the creation of younger craters and basins. Additionally, mare lavas partially fill several craters, creating smooth floors, which, with their bright rims, remind me of skating rinks. Plato and Archimedes are the best examples, with Endymion, Hercules, Condorcet, Goddard and Lyot being less well known. These ‘skating-rink craters’ are located on or near maria but don’t have broken rims. That means the lavas on their floors didn’t flow into the craters from outside; instead, the lava must have erupted onto the floors through basin fracture zones and…

Many years ago, I played a game called Gold of the Desert Kings as part of a team-building day at work. The goal was simple: Bring back as much gold from the desert as possible. Each team had the option to trade a turn for a chance to “ask the Old Man” for advice before setting out on a quest. My team didn’t stop to talk to the Old Man and, predictably, soon died of thirst, penniless, in the desert. Had we asked him for advice, the Old Man would have revealed the location of the oasis that could have kept us alive. Fast-forward 20 years, and now I’m the Old Man. While there’s no substitute for experience, it doesn’t always have to be firsthand experience. I’m hoping that some…

Steve Massey is a Queensland-based amateur astronomer who has previously worked at the Anglo-Australian Observatory. He is author or co-author of seven books on backyard astronomy and video imaging. What got you into astronomy? It was my first telescopic views of the Moon that ignited my passion. The vista of mountain ranges and deep, shadowy craters peppered across a curving surface made me realise this was truly another world. I started drawing maps and taking meticulous notes, to the point that my father complained my astronomy notebooks were tidier than my school homework. What was your first telescope set-up? A 40-mm refractor with a short tripod that my father bought me when I was nine. Most times I perched it on a wooden crate and at other times as my…

JUST AS THE AWFUL year of 2020, so full of loss, conflict, cynicism and pain, was drawing to a close, we Earthlings were treated to a rare and stunning celestial arrangement as the two bright gas giants Jupiter and Saturn pulled to within a fingernail’s width of each other. For those of us attuned to the sky, such a sight is not only a delight in and of itself, but it can pull us out of our quotidian reality. We enter into sky time, recalling other spectacles, other times and places when the stars aligned for us. We remember our favourite eclipses, rare meteor showers, auroral light shows, the few really good comets that have offered themselves to our close inspection, and those bright planetary congregations we’ve witnessed during our…