Indholdsfortegnelse for September - October 2020 i Australian Sky & Telescope

If our Solar System is any guide, moons should exist in abundance throughout the galaxy — perhaps reaching numbers as high as tens of billions. David Kipping was almost shaking with excitement. He was staring at a plot on his computer screen with a peculiar dip that kept reappearing no matter how he processed the data. It looked like the first glimpse of a moon beyond the Solar System. He left his desk and went for a walk. “I had to sit on a bench and take deep breaths to try and centre myself a bit because I was just, like, crazily excited about it — thinking ‘This is gonna be amazing, this is gonna change my life,’” he says. But Kipping, then a postdoc at Harvard University, also knew…

NEXT YEAR, EARTH WILL INVADE MARS. Launch opportunities to Mars occur once every 26 months, and during this year’s launch window — which spanned July and August — three spacecraft were set to begin their journeys. If everything goes well, in early 2021 they’ll deliver two orbiters, a lander and two rovers to Mars, joining the six orbiters, one lander and one rover that already operate there. Robotic spacecraft have orbited Mars continuously since 1997. The numerous missions have produced global maps of albedo, topography and composition, finding evidence for abundant shallow subsurface ice and a distant past of longterm environments suitable for life. NASA seeks to take the next step with its Perseverance rover, going beyond the search for habitable environments to the search for life itself. Perseverance won’t…

As an observer I’m both fascinated and haunted by cosmic dust. Under very dark skies the twisting, shadowy webs that wind through the Milky Way are almost hypnotic to trace. But at the same time, I’m frustrated by knowledge that every dark cosmic cloud is visible only because it obscures the light of the stars, nebulae and galaxies that lie beyond it. Other than a few cheats — like gravitationally lensed quasars, for example — everything we see up there, we see at the expense of something else. This is much on my mind when I observe the open cluster NGC 6124 in the southwestern corner of the constellation Scorpius, the Scorpion. That region of the galactic band is clotted with prominent dark nebulae and more elusive tendrils of cosmic…

Stargazers will be treated to two fine meteor showers over the next couple of months, the first of which will be the Southern Taurids. This show is active from around September 19 to November 20, with the peak on October 10. It generally produces slow-moving but bright meteors, sometimes with fireballs thrown in. (There’s also a companion shower coming up, the Northern Taurids, active from October 20 until early December and with its peak on November 12.) But the main shower during this period will be the Orionids, which is active from October 2 through until November 7, with the peak on October 21. This year the Moon will not interfere with viewing, having set in the very late evening and leaving dark skies for observation of this shower from…

For more than 350 years, scientific examination of the Moon was limited to observations made at visible wavelengths. Beginning in the 1960s, instruments coupled to telescopes and flown aboard lunar orbiting spacecraft began to detect previously unknown surface characteristics in images recorded at visible wavelengths and beyond. Perhaps the most famous are false-colour images revealing brightness variations within lava flows due to different chemical compositions in the lunar maria. The most prominent example is the dark band of lavas along the outer edges of Mare Serenitatis. Spectral imaging analysis identified this dark band as titanium-rich lavas, while the lighter-hued lavas seen elsewhere on the Moon were found to be titanium-poor. Furthering this trend of discovering previously unknown features beyond those apparent in visible light, the Diviner Lunar Radiometer Experiment on…

WHEN THE OPPORTUNITY ROVER discovered the first extramartian rock in May 2004, it seemed like such a delightful novelty. To travel all that way from our home planet to explore the Martian hills, dunes and craters only to stumble upon a rock that is not from that world! What are the chances that among all the places we could have roved we’d roll right up to this interloper on Mars? The chances are not all that poor, as it turns out. Between Spirit, Opportunity and Curiosity, we’ve so far encountered more than 20 of these aliens. How did Opportunity recognise that first outsider? It has the look of many iron meteorites on Earth — shiny, metallic and eroded with vesicles, or pits. Astute observers noticed that, strangely, these rocks seem…

The Australasian Dark Sky Association’s (ADSA) world-record attempt for the greatest number of people attempting an online sustainability activity — a one-night light pollution survey — on June 21 was a roaring success. A grand total of 4,283 people completed the allotted 30 minutes of helping to identify and map pockets of light, gathering 7,600 data points across Australia and New Zealand. The previous record was 2,000 participants. “We’ve had an overwhelming response from people sharing their experiences of stepping out and looking at the stars for the first time as a family, of children doing ‘show and tell’ about light pollution and of beautiful images from all around the world,” said ADSA CEO, Marnie Ogg. Find out more at the ADSA’s website, australasiandarkskyalliance.org. Still on light pollution, New Zealand…

A CHILD’S COLOURED PENCIL SET cannot possibly capture the sublime contours of light and shade displayed during a total lunar eclipse. Maroon, vermillion, carmine, crimson — recreating each hue would challenge the finest artists among us. I was no match for them, of course. It was July 1982, the night of a long lunar eclipse. Ten years old, with tortoise-shell eyeglasses perched under a boyish haircut, I was a misfit everywhere but in my backyard. There, I was an astronomer. It was the most spectacular night of my life. At half past midnight, an unthinkable hour for a child to be awake, I stepped outside. My mother stayed in the kitchen, preparing vital snacks. I opened my notebook, peered through my tiny telescope as Earth’s shadow started to creep across…

First image of a young sun and two giant planets THE EUROPEAN Southern Observatory’s Very Large Telescope (VLT) has captured an image of a young, Sun-like star and its two companions. Direct images of exoplanets are nothing new, but this is the first time researchers have directly seen multiple planets orbiting a star like our own. The star is only 17 million years old, a “very young version of our own Sun,” says Alexander Bohn (Leiden University, The Netherlands), who led the team that reported the results. But the system, dubbed TYC 8998-760-1, is nothing like our Solar System. One of the star’s companions straddles the line that defines planets, with a mass 14 times Jupiter’s; the other has a mass of six Jupiters. Both orbit far from the star,…

MOST PLANETS IN THE SOLAR SYSTEM have moons, but giant Jupiter has perhaps the most extraordinary satellite of all — the volcanic wonderland Io, a world made for superlatives. Its hundreds of active volcanoes erupt huge volumes of hot lava. Lava flows cover areas the size of small countries on Earth. And although it’s almost exactly the same size as Earth’s Moon and just as much a target for impactors, Io’s surface looks nothing like the ancient, heavily cratered lunar landscape — in fact, Io’s surface has no impact craters at all: The incredible level of volcanic activity constantly renews the surface and quickly buries all evidence of impacts. The most astonishing thing about Io, however, is that it is volcanic at all. When the worlds of the Solar System…

Another mission was originally intended for the 2020 flight window: ExoMars, a joint mission between the European Space Agency and the Roscosmos agency in Russia, would have put the Rosalind Franklin rover on the Red Planet’s surface in 2021 as well. However, parachute problems put the mission behind schedule, causing the team to delay to a 2022 launch. Like Perseverance, the Rosalind Franklin will be on the lookout for life, but it will take a different tack to the search for biosignatures. Rather than caching samples for future study, Franklin will drill as deep as two metres into Mars, retrieving samples to analyse in the lab within its belly. It will study each sample using infrared and Raman spectrometers, before using lasers to zap it into gases for analysis with…

The Ring Nebula and I go way back. Despite my lousy star charts, it was still the first deep sky object I ever found. I’d been looking for M57, as it’s also designated, with my 75-mm f/15 Tasco refractor for weeks without success until I finally swept up the 8.8-magnitude treasure between Beta (β) and Gamma (γ) Lyrae. Wow, was that exciting! It was 1968 and seeing that tiny, surreal oval with its dark central hole for the first time ignited my passion for deep sky observing. I also wondered what it might look like through a larger scope. Would I be able to see its famously difficult central star? I proceeded to order a mirror-making kit from Edmund Scientific — an event that ushered in my aperture fever. “The…

THE RED PLANET WILL REACH one of its best recent oppositions on October 14, when it will be just 62.7 million kilometres from your front door — close enough to outshine planetary kingpin Jupiter, and large enough for satisfying telescopic views of the Martian surface. Mars will actually be about 664,000 kilometres nearer on October 6, when it has its closest approach to Earth. Martian perihelion occurred on August 3, and ever since then the planet has been slowly moving away from the Sun, while at the same time Earth has been catching up in its orbit. The result is the October 6 ‘sweet spot’ — a compromise between Mars’ increasing solar distance and proximity to Earth. Mars circles the Sun in a slightly elliptical orbit, and so its distance…

Perry Vlahos is a long-time member of the Astronomical Society of Victoria (ASV), and an active promoter of all things astronomical via the media and special events. What got you into astronomy? If my father’s story of holding me up in his arms as a baby to look at a comet is true, then it goes back a long way. But consciously it began with my first science lesson in year seven. The teacher drew a semicircle on the board, plotted dots on it with exotic names like Aldebaran and Betelgeuse, joined some up, then asked us to copy it all down in our books and go out that night to find them. After finding them all, I was hooked. What was your first telescope set-up? I received a cheap…

For nearly 2,000 years, since the time of the ancient Greek thinkers, conventional wisdom in the west maintained that the Earth and the universe that enclosed it are very different. The Earth stood still at the centre of all things, while the heavens revolved around it. But the Earth was subject to change and decay, while, at least beyond the orbit of the Moon, all was eternal and unchanging. Great minds in the 17th and 18th century steadily dismantled that understanding. Copernicus and Galileo moved the Earth from the centre, replacing it with the Sun. Newton proved that events on Earth and in the wider universe followed the same laws of motion and that all was subject to the force of gravity. At that level, the Earth and the Universe…

LARGE-FORMAT CMOS Finger Lakes Instrumentation (a division of IDEX Health & Science) adds a new large-format CMOS to its line of professional-grade astronomical cameras. The Kepler KL6060 Cooled sCMOS camera (starting at US$45,000) is designed around a huge, 37.7-megapixel monochrome sCMOS detector with 10-micron-square pixels in a 6,144 x 6,144 array measuring 86.8 mm from corner to corner. Thermoelectric cooling allows stable temperatures of down to 45°C below ambient. Combined with low 4.6e- read noise, this results in smooth, noise-free images. The unit is capable of recording 11 full-resolution, 12-bit frames per second through its USB 3.0 interface, or 19 frames per second when using an optional QSFP fiber interface. Faster rates are possible when using a small region-of-interest. The camera is available with a standard front-illuminated detector with a…

THERE’S AN OLD STORY about a bunch of miners sheltering in a hut. They have a joke book, but everybody has read it so often they’ve memorised it, so when someone wants to tell a joke they simply call out the page number. Well, the ‘big, bold, bright and beautiful’ highlights I’ll cover in this article are a bit like that. The sky region we’ll be looking at — Sagittarius and its neighbours — contains just so many amazing deep sky sights. Why? Because when we look in that direction, we’re gazing right into the gravitational hub around which everything else in our galaxy revolves. Globular clusters hover around it like bees around a hive, nebulae (both bright and dark) abound and the sky is thick with stars. Toward the…

You don’t have read much about astronomy before coming across mentions of the variable star P Cygni, or the term ‘P-Cygni profile,’ which refers to the spectroscopic signature of gaseous stellar outflows, named after those of the star. P Cyg first appeared as a third-magnitude star in the year 1600, not long after another new star had appeared in 1572 in Cassiopeia. These were the literal ‘novae,’ or ‘new stars’. The much brighter 1572 nova was actually the result of a destructive supernova (SN 1572) whereas P Cyg is now known to be a ‘luminous blue variable’ that underwent an eruptive event. Unlike the one-off SN 1572, P Cyg remained bright for several years. After some decades of brightening and dimming, the star has ranged between magnitude 4.6 and 5.6…

With winter ending, the nights are starting to get warmer — a perfect time to embark on a mission to Neptune, coldest and most distant planet in the Solar System. Thankfully, you’ll probably only need to wear a jumper for a backyard visit with your telescope, but if you could transport yourself to this distant world, a well-heated spacesuit would be an absolute must. Neptune’s atmospheric temperature averages around –212°C, which is cold enough to turn carbon monoxide and methane into ice crystals. Indeed, it’s methane that first catches your attention at the eyepiece. Neptune’s upper atmosphere comprises 1.5% methane, which absorbs red light from the Sun and reflects blue, making it the Solar System’s other ‘blue planet’. When I observe this pale dot, I sometimes like to imagine I’m…

COMETS ARE PERHAPS the oddest denizens of the Solar System. Most appear with little warning, put on a modest show, then race back to the Oort Cloud, not to be seen again for many, many years. Part of their allure is that each is unique and doesn’t always follow predictions about its brightness and activity. Some, like 17P/Holmes, defy conventional wisdom and unexpectedly attain naked-eye visibility even when located relatively far from the Sun. Others fail to live up to their advance billing, with some inevitably disintegrating as they near our star. All this uncertainty is part of the challenge that has kept me actively photographing comets for more than 30 years. Dirty iceballs These dusty chunks of ice and gravel are leftover material from the formation of our Solar…

LUNAR DETAIL David Hough This crisp lunar image was made by stacking and processing thousands of individual frames from a 56 GB video file. David used a William Optics FLT 132 refractor and a ZWO ASI294MC Pro camera, with the video captured in ASIStudio 1.1 and processed with AutoStakkert!3, RegiStax 6 and Photoshop 5.…