Innholdsfortegnelse for November - December 2021 i Australian Sky & Telescope

THE EVENT HORIZON TELESCOPE collaboration has peered deeply into the heart of the radio galaxy Centaurus A, revealing details of its long, powerful jets. Cen A lies only about 12 million light-years from us and hosts a supermassive black hole that’s actively swallowing gas and shooting out a narrow jet from top and bottom. The team used seven facilities across half the globe to image the jet at radio wavelengths. Based on years of detailed simulations, astronomers think that the centre of a black hole’s jet (its ‘spine’) is largely empty — it’s essentially a giant, corkscrew-like magnetic field with a few electrons and other particles zooming through, explains team member Michael Janssen (Max Planck Institute for Radio Astronomy, Germany). An immense number of particles, blown off the black hole’s…

As with so many of the Greek astronomers who got the science going more than 2,000 years ago, we know little more than the basics about the life of Hipparchus. Evidence suggests he was born in Nicaea in modern Turkey around 190 BCE and died in Rhodes some 70 years later, but that is about all. Likewise we have almost no accounts of his discoveries in his own hand. He reputedly wrote 14 books but only one has survived. The rest are long lost, together with so much the science and literature of the ancient Greeks. But the writings of later astronomers contain many references to his achievements, showing how productive and well-regarded he was. Much of what the highly influential Ptolemy wrote in his famous Almagest a few centuries…

IF LENSES COULD BE BUILT as large as utes and thinner than their windshields, then we would probably still find them in many big telescopes, including those in space. Lenses are more resilient to misalignment and small defects than mirrors are, making lens-based devices potentially simpler, sturdier and more reliable — as well as cheaper to launch. But astronomers largely abandoned refractor designs for large telescopes early in the 20th century, mainly because of the lenses’ massive weights. However, a group of astronomers and engineers at the University of Arizona might have found the key to making large, lens-based space telescopes a reality. Led by Daniel Apai and Tom Milster, they have come up with a lens design that combines refractive and diffractive elements and can reach several metres in…

We’ve arranged astronomers’ predictions into a rough timeline, with probability rankings and approximate fulfillment dates. Many are safe bets; a few aren’t. Things become more uncertain after 2030.…

A constellation doesn’t have to be bright to be interesting. For instance, there’s Capricornus, the Sea Goat or Goat-Fish — the mythological creature’s front half is goat and its back half is fish. Interesting indeed! And yet, this mix-and-match figure’s brightest stars are only of 3rd magnitude. Along the zodiac, Capricornus follows showier Sagittarius, the Archer. Sagittarius not only has brighter stars, but it’s also richly endowed with the glorious central region of the Milky Way and a host of deep sky treasures, including 15 Messier objects. Capricornus, by comparison has just one Messier — globular cluster M30. If your sky is light polluted, you might struggle to locate Capricornus. However, in November and December both Jupiter and Saturn visit the constellation. The bright duo should make finding it a…

As mentioned in the previous issue, the ‘Rosetta comet’ 67P/ Churyumov-Gerasimenko will reach perihelion on November 2 at 1.21 a.u. (180 million km) from the Sun. This year’s apparition is a rather favourable one, with the comet beginning November in Gemini at a predicted magnitude of 9 or thereabouts — well within the range of large binoculars. By the end of the second week of the month, it will enter the faint constellation Cancer where it will remain throughout the period, slowly fading to around magnitude 10 by the close of the year. This comet will be joined by another well-known object of short period in December. Comet 19P/Borrelly will reach perihelion on February 1, 2022, at a distance of 1.31 a.u. (196 million km) from the Sun. This will…

DEEP SKY ASTROPHOTOGRAPHY has many challenges, particularly when practiced under less-than-ideal skies. The difficulty of imaging through light pollution and poor seeing limits the targets you can capture to bright objects often recorded at low resolution. Additionally, long spans of cloudy weather can further reduce your output. Fortunately, astrophotographers no longer have to remain tethered to equipment in the backyard, nor be forced to travel far afield for clear, steady, dark skies. The availability of high-speed internet even in remote locations has fostered the growth of remote-imaging facilities, where astrophotographers willing to invest in the support and maintenance of their equipment can capture deep sky wonders under some of the most pristine skies on Earth. Here are my suggestions for getting great results delivered to your computer each clear night.…

WE LIVE IN AN AMAZING TIME. For the first time ever, we have developed the means to potentially spot life in our galaxy, if it is out there. The upcoming James Webb Space Telescope and ground-based 30-metre-class telescopes will open our eyes to thousands of new worlds in our celestial neighbourhood, burnishing our hope of finding other Pale Blue Dots. In our search, transiting exoplanets feature prominently. Such worlds block a tiny part of their host star from our view when they pass between us and the star. That’s when we notice them. We can’t see most of the exoplanets directly, but we know they’re there, because we can detect that slight dimming with a precision like clockwork. Some of these worlds are at just the right distance from their…

NASA’S INSIGHT MISSION has reported the first direct observations of another rocky planet’s interior structure. The results — a surprisingly thin crust, a one-layer mantle and a large core — will help scientists understand how Mars formed and evolved. Measuring marsquakes wasn’t just a matter of sending a seismometer to Mars; in a sense, the scientists also had to wait for the planet to come to them. While Insight recorded 733 marsquakes since early 2019, the vast majority were weak, surface tremors. “Of course, when you’re in the middle of the situation, it can feel as if ‘Oh my god, it’s not working!’” says Simon Stähler (ETH Zurich, Switzerland). The team waited several months after the seismometer’s deployment before a shake occurred deep enough to probe the planet’s interior, says…

ASTRONOMY 2022 YEARBOOK Every astronomer needs the Astronomy 2022 yearbook. Packed full of essential information to plan your observing sessions, it is a complete guide to what’s visible in the night sky, including Moon phases, planets, comets, eclipses, meteor showers and occultations, plus star maps and detailed monthly viewing guides. $29.95 + postage & handling 2022 AUSTRALASIAN SKY GUIDE The easy-to-read 2022 Australasian Sky Guide provides a month-by-month guide to what can be seen with the naked eye, along with lots of interesting facts and figures, detailed descriptions of special astronomical events, and planetary data. This is an ideal gift for novice astronomers and kids. $16.95 + postage & handling ASTRONOMY 2022 CALENDAR Featuring amazing photography from the annual David Malin Awards, the Astronomy 2022 Calendar provides a guide to…

ASTEROID 16 PSYCHE is the largest metallic object in the main belt and the destination of NASA’s eponymous mission, set to launch in 2022. But what the spacecraft will see when it arrives remains an open question. Evidence is mounting that it will discover a world that once oozed iron lava, a phenomenon known as ferrovolcanism. The apparent presence of iron on Psyche’s surface initially led astronomers to propose that the asteroid is a planetary core, exposed long ago via violent collisions. However, subsequent measurements revealed that the asteroid’s overall density is surprisingly low, so it might be a porous rubble pile instead. Then, in 2020, Brandon Johnson (Purdue University) and colleagues suggested that ferrovolcanism on a differentiated body could have resulted in a metallic surface despite its low density.…

RADIO WAVELENGTHS give astronomers access to an unseen universe, from stellar flares to jets launched from supermassive black holes. But arguably, we have yet to take advantage of the best place in the inner Solar System for low-frequency radio astronomy: the Moon. The lunar farside always faces away from Earth and is thus radio-quiet, shielded by the Moon itself from radio-frequency interference coming from powerful Earth-based transmitters. The Moon also lacks a substantial ionosphere, whereas Earth’s ionosphere absorbs and refracts cosmic radio sources. Furthermore, the lunar environment is dry and stable, leading to steadier radio observations. Radio astronomy from the Moon is not a new idea — astronomers proposed a lunar radio observatory at a science symposium in 1965, before Apollo 11. In a separate endeavour, NASA’s Radio Astronomy Explorer…

TELESCOPES ARE POWERFUL TOOLS of exploration, enabling humans to probe far beyond where we can go ourselves or with robots. And arguably no instrument better embodies the advances spurred by our cosmic curiosity thus far than the James Webb Space Telescope. Scheduled to be ready for launch by October 31 when this article went to press, Webb is the long-awaited scientific successor to the Hubble Space Telescope and promises to be the world’s premier space observatory. Even before the Hubble Space Telescope launched in 1990, scientists were considering what machine ought to follow it. Hubble ‘sees’ primarily ultraviolet and visible light, with some capability to observe at the shortest near-infrared wavelengths. Scientists understood even then that, as mighty as Hubble would be, its 2.4-metre primary mirror and suite of instruments…

Binoculars offer a wonderful, wide window into the cosmos. Their expansive views are perfect for capturing big open star clusters, and for scanning rich, Milky Way star fields. But no single tool is perfect for every application. A spoon makes a lousy knife, and a knife makes a lousy spoon. And so it is with binoculars and telescopes. Targets that call for a lot of magnification are especially challenging for binos. Globular clusters fall into this category — some are absolutely stunning through a telescope at high magnification but can be tricky with binoculars. Nonetheless, some are pretty easy through binos, and M15 in westernmost Pegasus is a shining example. A number of factors work in M15’s favour. First, at magnitude 6.2, it’s one of the brightest Messier globulars —…

It’s sometimes said that astronomical seeing can be judged by how many stars can be seen in the Trapezium Cluster in the heart of the Orion Nebula. But as we will see, this is not a good idea. The Trapezium, aka Theta1 Orionis, is the powerhouse that lights much of the surrounding nebula. All four of the brightest components of Theta1 Ori — A, B, C and D — along with Theta2 Ori A, B and C, are both multiple and variable. In fact, on the chart on this page, every star bar two is variable. Even with the limiting magnitude of 11.5 there are hundreds of variables omitted from this chart. The Theta stars have given rise to their own class, type IN, the Orion variables. For example, V361…

WI-FI CONTROLLER ZW Optical has announced the latest version of its smart Wi-Fi controller for astrophotographers. The ASIAIR Plus (US$279) lets you power and control your camera, focuser, autoguider and Go To mount using your Android or iOS smart device. The ASIAIR Plus is a mini-computer with a 1.5 GHz CPU, 4GB of DDR4 memory and 84GB of internal storage. Smaller and lighter than its predecessors, it’s housed in a CNC-machined casing that attaches directly to your telescope or mount. It includes four female 5.5 × 2.1-mm, 12-volt DC outputs, two each of USB 2.0 and 3.0 ports, and a 2.5-mm DSLR shutter release port to control Canon, Nikon and ZWO imaging equipment. The unit connects to your smart device via a Wi-Fi antenna — with greater range and reliability…

I WAS STOKED WHEN I heard they were putting microphones on the Perseverance rover. Of all the instrument data we use to understand other planets, visual images are always the most compelling because they connect directly to our senses, with no interpretation needed to grasp a lot about each new place. Sound recordings ought to do this as well: provide something we can relate to directly and feel what it would be like to be there. Shortly after the thrill of the rover’s landing at Jezero Crater in February, we were treated to the first release of audio from Mars. What we heard, of course, was wind. We already knew that the Red Planet has wind, but when we finally heard it, we learned that wind on Mars sounds… like…

The winning images in two premiere astrophotography competitions have been announced, and they include some amazing and impressive shots of the night sky. First up is the David Malin Awards, organised every year by the Central West Astronomical Society based at Parkes in NSW. The overall winner this year is Marley Butler for his image entitled ‘Between a Rock and Outer Space,’ which depicts the Milky Way stretching above a piece of rocky coastline in Western Australia. The judges described the image as “… a lovely montage. What makes it work is the overall colour balance, the evident but not dominant rocky foreground and the softened, time-exposed sea. The stars are pin-sharp, and the Milky Way embraces the whole thing, including the zodiacal light. Beautiful!” There are also specific winners…

RESEARCHERS HAVE IDENTIFIED dozens of radar-bright spots within the layers of ice and sediment deposits at Mars’ south pole. These discoveries follow the 2018 announcement of a large radar-bright area beneath those deposits that researchers said might indicate a subglacial lake. However, the additional finds, as well as further experiments and analysis, suggest that the spots might be ancient clay deposits instead of liquid water. In a study published in the July Geophysical Research Letters, Aditya Khuller (Arizona State University) and Jeffrey Plaut (Jet Propulsion Laboratory) used the Mars Advanced Radar for Subsurface and Ionosphere Sounding (MARSIS) instrument aboard the European Space Agency’s Mars Express orbiter to chart the subsurface boundary where the polar deposits end and the Martian interior begins. Their investigation revealed dozens of new smaller radar-bright regions…

ASTRONOMERS HAVE UNCOVERED four candidate Earth-mass rogue planets by searching for microlensing events observed with NASA’s Kepler satellite. Rogue planets drift aimlessly through space after ejection from their stellar system during the early stages of planet formation. When a star or planet passes in front of a distant star, it acts like a magnifying lens to temporarily brighten the background star, an effect known as microlensing. Rogue planets are best spotted via microlensing because they’re too faint to detect directly. However, the smaller the ‘lens,’ the shorter the microlensing event; Earth-mass planets magnify background stars for only a couple of hours, making them difficult to differentiate from stellar flares. A team lead by Iain McDonald (now at Open University, UK pored through data from the rejuvenated Kepler mission, dubbed K2,…

CASSINI. NEW HORIZONS. The Hubble Space Telescope. These spacecraft and so many others have given us mesmerising views of the cosmos, expanding our knowledge and piquing our curiosity. But it’s no use sending instruments to space if we can’t get the data back. Without a communications link, there is no exploration. Throughout the Space Age, we’ve used radio wavelengths to transmit data to and from our space emissaries. Radio has major perks: It cuts through clouds above ground stations, and its wavelengths are so long that you don’t have to aim too carefully in order to hit your antenna back on Earth. But radio is also slow. Those same long wavelengths limit how much information a signal can carry. Take, for instance, the New Horizons spacecraft, which due to distance,…

IN THE LAST DECADE, the notion of interstellar travel went from fiction to reality. In 2012, after 35 years of interplanetary travel across 122 astronomical units, Voyager 1 left the Ssolar System and crossed into interstellar space. In 2018, Voyager 2 did the same. But the only other transmitting spacecraft on a trajectory to interstellar space, New Horizons, is not even halfway there. The scientific community’s tenuous connection to this unexplored region therefore depends on the 44-year-old Voyagers staying alive or the New Horizons craft surviving another couple decades. Unless we send a dedicated mission to interstellar space. US astronomers have proposed interstellar missions since 1960; since then, NASA and the European Space Agency (ESA) have entertained a couple of dozen mission concepts, none of which have come to fruition.…

We’re going to be treated to two eclipses across November and December, but your viewing location will heavily determine what you get to see. First up is a deep partial lunar eclipse on November 19, visible across Australia, the Pacific, eastern Asia, the Americas and northern Europe. The partial phase — when the Moon enters Earth’s umbral shadow — will begin at 7:18 UT and greatest eclipse will be at 9:03 UT. At maximum, 97% of the lunar disk will squeeze into the umbra, leaving just a narrow sliver of the southern limb poking out. The Moon will be just 1.7 days shy of apogee, so its apparent size will be slightly smaller than usual. This helps increase both the depth of the eclipse and its duration. The Moon will…

WHEN Late October 11 pm Early November 10 pm Late November 9 pm These are daylight savings times. Subtract one hour if daylight savings is not applicable. HOW Go outside within an hour or so of a time listed above. Hold the map above your head with the bottom of the page facing south. The chart now matches the stars in your sky, with the curved edge representing the horizon and the centre of the chart being the point directly over your head (known as the zenith). FOR EXAMPLE Look at the chart, and you’ll see that the bright star Canopus in the constellation Carina is about a third of the way between the south-eastern horizon and the middle of the chart. So if you look into the south-eastern sky,…

Lunar rilles, or rimae, are long, narrow trenches that often go unnoticed at the telescope. In the late 1680s, Dutch astronomer Christiaan Huygens detected the features later named Schröter’s Valley and Rima Hyginus. About 120 years later, German observer Johann Schröter rediscovered the valley that bears his name today and included it in his catalogue of 11 linear depressions that he called ‘rilles,’ the German word for grooves. Understanding their origins starts by noting that rilles have three different morphologies and distributions. In general, the biggest and easiest to see are linear rilles. The widest and deepest on the Moon is Rima Ariadaeus, found west of Mare Serenitatis. This rille measures 4.5 kilometres wide, 425 metres deep and 245 km long. Apollo 10 astronauts photographed an oblique view of the…

THE AVAILABILITY OF MODERATELY priced, quality eyepieces continues to grow with the new Meade Instruments Series 5000 UHD eyepieces. Currently the line includes four models that fit 1¼-inch focusers and have focal lengths of 10 mm (priced at US$120), 15 and 18 mm (US$140 each) and 24 mm (US$200). There’s also a 30-mm model (US$245) that’s made for 2-inch focusers. The latter eyepiece wasn’t available at the time we borrowed the other four for testing. The UHD series features ‘flat field’ performance, which is a somewhat vague description for eyepieces, but most of us will translate that as an eyepiece showing quality star images across its entire field of view. And the UHDs do indeed deliver well on that front. But there’s more to this flat field performance that I’ll…

We’ve all seen bits of comet dust self-immolate as they plow into Earth’s atmosphere during meteor showers. But did you know that bits of dust ping the Moon as well? Meteoroids — to give them their official name — that hit the Moon have no medium in which to burn up and instead slam full-throttle into the lunar surface. In so doing, they carve out a small crater while emitting a very brief flash of light. The Moon gets walloped. In November 1999, David Dunham (doyen of the International Occultation Timing Association) anticipated a particularly active Leonid meteor shower. He coordinated a network of observers armed with scopes and video cameras and instructed them to point at the Moon. Dunham himself observed at fellow astronomer George Varros’s home. Brian Cudnik…