Innholdsfortegnelse for November/December 2018 i Australian Sky & Telescope

WHEN I WAS IN MY TWENTIES, I lived quite close to the Sydney headquarters of the Anglo-Australian Observatory (AAO). Upon launching my astronomy magazine, Southern Astronomy (which later became Sky & Space), I used to regularly visit the AAO to delve into its fabulous library, speak with the astronomers, and — most enjoyably — call in on astrophotographer extraordinaire David Malin, to see what wonders he had come up with since my last visit. In those heady days of the 1980s, when the AAO was in its second decade, David was one of the people most responsible for helping bring astronomy to the masses by virtue of his colour images of the cosmos. I remember him showing me his new technique of unsharp masking — done manually with photographic plates…

ASTRONOMERS USING A NEW instrument on the Very Large Telescope (VLT) in Chile have directly imaged the youngest planet known to date. The data suggest that giant planets come together quickly and, once formed, regulate further growth of their host star. The star PDS 70 is only about 5 million years old and is still growing, accreting mass from a surrounding disk of gas and dust. Within the gaseous swirl, researchers had previously found a dark gap. But while disk gaps are often taken to be the signature of a newborn planet, other processes can create gaps, too. To explore further, Miriam Keppler (Max Planck Institute for Astronomy, Germany) and colleagues used VLT’s SPHERE adaptive optics system, discovering a point source dubbed PDS 70b within the disk’s gap. The astronomers…

OUR NEIGHBOUR GALAXY ran into a large companion billions of years ago, astronomers claim in the July 23 issue of Nature Astronomy. Richard D’Souza and Eric Bell (both at University of Michigan) examined independent, large-scale simulations to understand how Andromeda-size galaxies form. To reproduce our neighbour’s massive and metal-rich stellar halo, the simulations require a major collision within the past 5 billion years, with disrupting effects continuing until 2 billion years ago. The researchers conclude that M32, Andromeda’s satellite, is the most likely remnant of the encounter. The parent galaxy, dubbed M32p, was likely similar in mass to the Milky Way. The collision explains many of the galaxies’ characteristics, D’Souza says. A gravitational encounter could have triggered Andromeda’s bout of star formation 2 billion years ago, when the merger ended.…

Mercury (6.7", mag. –0.3) begins November in the western post-sunset sky, in company with Jupiter. The innermost planet will reach greatest eastern elongation on November 7 before heading toward the horizon and inferior conjunction on the 27th. Reappearing in the eastern morning sky in December, Mercury will reach greatest western elongation on the 15th. Jupiter, having undergone superior conjunction in late-November will once again join Mercury in the morning sky, with the two planets coming as close as 0.8° apart on December 22. Venus (52", –4.7) spent most of 2018 as the ‘evening star,’ but has reappeared from the glare of the Sun (having reached inferior conjunction on October 26) and is now gracing our morning skies before dawn. If you have a clear horizon, look for the planet close…

Next year is the 150th anniversary of first light for the 48-inch Great Melbourne Telescope (GMT). For more than two decades after the English-mounted reflector was completed in 1869, the GMT was the largest equatorial telescope in the world, and it remained the largest telescope in the Southern Hemisphere until 1922. Its users’ early achievements include the first visual observation of the spectrum of an extragalactic nebula (1870), the world’s finest photographs of the Moon (1872), the first photographs of southern nebulae (1883) and the discovery of more than 50 nebulae and galaxies. However, the GMT eventually fell on hard times. Challenges in printing delicate nebulae sketches plus a worldwide financial crisis in the 1890s that took its toll on Australia, prevented the publication of two decades of observations, making…

About 30 kilometres to the southwest of Atherton in far north Queensland is the former mining town of Irvinebank. Little remains of the town today; the population is supposedly 150. Remnants of the mining plant are rusted and growing back into the scenery. A museum has replaced the owner’s house and the artificial lake developed for the smelting process now attracts birds and grey nomads. There are seven children in the junior school. There is no senior school. But 100 years ago this now passed-over settlement was home to one of the largest industries in Queensland, if not in Australia, and its population was about 1250. Here, the Vulcan mine extracted tin from a record depth of 454 metres below the ground and smelted the ore in a purpose-built refinery.…

FOLLOW-UP OBSERVATIONS ACROSS the electromagnetic spectrum have helped scientists pinpoint the source of a single high-energy neutrino — a particle that has no electrical charge and almost no mass. The IceCube collaboration announced the probable birthplace of the neutrino, dubbed IceCube-170922A, in the July 13 issue of Science. The neutrino ghosted through our planet on September 22, 2017, before crashing into an atom in the Antarctic ice. The collision produced a heavy cousin of the electron called a muon, which left a track of dim, bluish light in the IceCube detector. Backtracking from the muon’s trajectory, a computer cluster calculated the source’s location on the sky and sent an automated alert to telescopes around the world just 43 seconds after the event. Within hours the space-based Neil Gehrels Swift Observatory…

ASTRONOMERS WORKING with data from the European Space Agency’s Gaia mission have discovered a new feature due to a change in the structures of low-mass stars. Astronomers often use the century-old Hertzsprung-Russell diagram to determine stars’ properties based on their colour and brightness. Now, a team of astronomers led by Wei-Chun Jao (Georgia State University) has announced the discovery of a narrow but distinctive gap in this diagram. While most stars follow a smooth continuum, a tiny hiccup appears in the luminosities of low-mass M stars. The gap in luminosities corresponds to the mass where M stars transition from a fully convective interior to a structure more like the Sun’s, with a convective envelope surrounding a denser, radiative core. Most theoretical models of stellar structure don’t predict this hiccup. Yet…

NASA’s Glenn Extreme Environments Rig (GEER) enables researchers to simulate planetary conditions in a chamber a little smaller than a refrigerator. Last year, they exposed various mineral, rock and glass samples to Venusian conditions for 80 days to see what reactions would take place. Researchers have also exposed different kinds of high-temperature electronics, some of which survived, says NASA’s Jim Green. That success might open the door to small, long-lived landers.…

The Milky Way is such a colossus that only eight other galaxies within 20 million light-years rival its size, mass and luminosity. Remarkably, all of the great galaxies nearby occupy the same plane, one that is proportionately even thinner than a typical coin: the Milky Way and Andromeda Galaxies, the two superpowers of the Local Group; the giant spiral galaxy M81 in Ursa Major; the giant elliptical galaxy Maffei 1 and its giant spiral neighbours Maffei 2 and IC 342, which all hide behind interstellar dust in Cassiopeia and Camelopardalis; the giant edge-on spiral galaxy NGC 253 in Sculptor; the giant elliptical galaxy Centaurus A and the giant barred spiral galaxy M83 in Hydra. This plane nearly coincides with the so-called supergalactic plane, which includes the Virgo Cluster. In supergalactic…

WHEN Late October 11pm Early November 10pm Late November 9pm 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 southeastern horizon and the middle of the chart. So if you look into the south-eastern sky, you’ll find Canopus…

This month’s target is the southern dwarf nova VW Hydri. Dwarf novae are accreting binary stars, comprising a white dwarf, an accretion disc and a lower-mass donor star — complicated systems about which there is much not known. VW Hydri is classified as an SU Ursae Majoris-type star. Systems of this kind exhibit two types of outburst: normal outbursts and so-called superoutbursts of longer duration and greater amplitude. VW Hyi flickers away in quiescence at 14th magnitude but every few weeks rises to 10th magnitude for two or three days, and less frequently to 9th magnitude for 10 to 18 days in a superoutburst. Compare this to the SS Cygni-class of dwarf nova discussed in this column in our May/June issue. Being so bright, VW Hyi is almost routinely the…

TOUTED AS THE ‘mission to touch the Sun,’ the Parker Solar Probe is the first to be named after a living person, solar physicist Eugene Parker (University of Chicago, emeritus). The spacecraft will carry a suite of instruments to study the origin of the solar wind and the dynamics of the solar corona, looping around the Sun 24 times in its seven-year mission. After its launch on August 12, the probe is due to swing by Venus on September 28, entering an initial, 150-day-long orbit around the Sun. Passing 34.7 solar radii from the Sun on November 1, it will complete six additional Venus flybys to further decrease its period to 88 days. Ultimately, the spacecraft will reach it closest approach, passing within 9 solar radii of the Sun’s surface,…

Small satellite to answer big question HaloSat, a CubeSat deployed from the International Space Station on July 13, is on the hunt for the universe’s missing mass. While the identity of dark matter remains a mystery, even ‘normal’ baryonic matter isn’t all accounted for: Astronomers tallying up stars, planets, galaxies, gas and dust only come up with about half of the expected mass. Some of this missing matter may reside in million-degree gas that surrounds galaxies, but the temperatures are so extreme that observational signatures are faint. HaloSat detects X-rays with energies between 400 and 2,000 electron volts, which enables it to find emission from ionised oxygen associated with superhot halo gas. With a 100-square-degree field of view, HaloSat will efficiently survey the entire sky to determine the extent of…

THE MOST INTERESTING WORLDS are those that are most varied and vibrant. Consider Earth. Lying between its churning interior and solar-driven atmosphere, its surface is continually reworked, producing infinite diversity and beauty. Maybe I’m biased, but that winning combination of vigorous internal and atmospheric activity makes for the best planetary exteriors. Fortunately, we keep finding more places where the fertile interface between geology and meteorology cooks up marvels. Such features are often a beguiling mix of the familiar and the exotic, with recognisable forms assembled from available materials that are malleable in the extreme (to us) conditions found on other worlds. On Titan, for example, a hydrological cycle creates recognisable fractal rivers and lakeshores, but the working fluid is methane, not water. Pluto, as revealed to us by the New…

The Internet makes it easy for us to enjoy impressive images of planets, nebulae, star clusters and galaxies with just a few mouse clicks. Virtually any Messier or NGC object can be found online, usually shown with plenty of colour and detail. But it wasn’t always so easy. After Henry Draper and others pioneered astrophotography in the late 1800s, it took nearly a century before one individual developed a reliable technique for producing colour astrophotographs that is still in use in the digital age. New eyes under southern skies Since most of the planet’s population lives north of the equator, it’s not surprising that many of the world’s largest telescopes were located there until the end of the 20th century. By the 1960s, huge instruments such as the 5-metre (200-inch)…

NOVEMBER 6 Venus 10° south of Moon 7 Mercury greatest elong. east (23°) 9 Mercury 1.8° north of Antares 9 Mercury 7° south of Moon 12 Saturn 1.5° south of Moon 14 Venus stationary 16 Mars 1.0° north of Moon 17 Mercury stationary 17 Neptune 3° north of Moon 21 Uranus 5° north of Moon 26 Jupiter in conjunction with Sun 27 Mercury in inferior conjunction 29 Moon 2° north of Regulus DECEMBER 2 Venus greatest illuminated extent 4 Venus 4° south of Moon 6 Mercury 1.9° south of Moon 7 Mercury stationary 15 Neptune 3° north of Moon 15 Mars 4° north of Moon 15 Mercury greatest elong. west (21°) 18 Uranus 5° north of Moon 20 Jupiter 5° north of Antares 21 Mercury 6° north of Antares 21…

JUPITER FADES FROM the evening sky in November, to reappear in the morning sky in December. The planet will be fairly bright, shining at around magnitude –1.7 for the balance of December. Jove will grow just a trifle heftier too, fattening from 31” to 32” by New Year’s Eve. As observing conditions improve, it will be easier to detect Jupiter’s moons. Any telescope will show the four big Galilean moons, and binoculars will usually show at least two or three. Following are the times, in Universal Time, when the Great Red Spot should cross Jupiter’s central 1 meridian. The dates, also in UT, are in bold. Dec. 1, 2:24, 12:20, 22:16; 2, 8:12, 18:08; 3, 4:03, 13:59, 23:55; 4, 9:51, 19:47; 5, 5:43, 15:38; 6, 1:34, 11:30, 21:26; 7, 7:22,…

I CONTINUALLY HEAR PEOPLE FRET about the decline in popularity of amateur telescope making. While there is some truth in this, Zane Landers is quietly proving that fear to be unfounded. Zane has been into astronomy since he was 12, which was only three years ago. He started with a 10-cm Go To Maksutov that he got for Christmas, but soon became frustrated with the telescope’s computer system and its small aperture. He switched to a 15-cm Newtonian, which he reports “had good optics and worked very well except for the fact that it weighed 31 kg, looked really ugly, and had stray light problems due to its very short tube.” So he tried a 100-mm refractor, which was lighter and more attractive than the Newtonian but was uncomfortable to…

LOVELY LAMBDA Simon Johnson Lambda Centauri is a star about 40 light-years away, one of the closest to our Solar System. In this image (taken through H-alpha, O III and S II filters; 30 one-minute sub-frames each) it is the bright, ‘yellow’ star in the bottom-right of the picture (although it is, in fact, a blue star). The nebulosity is IC 2944. Simon used a ZWO ASI 1600MM-C camera and processed the data with PixInsight and Photoshop. GALAXY ABOVE Mark Beeksma Taken from a dark sky site in southern Sydney, Mark’s shot of the winter Milky Way was taken with a Canon EOS 6D camera. It’s a composite of 12 tracked and 4 untracked images. NEPTUNE Dave Manning The eighth planet from the Sun looms out of the darkness in…

Mars: The inside story After NASA’s Insight mission lands in November, scientists hope to learn what goes on deep in the Red Planet’s interior. Return to the Iron Planet An ungainly stack of satellites is set to double the number of spacecraft that have visited Mercury. Backyard astrophotography Imaging from a suburban backyard can be rewarding, even under light-polluted skies. We show you how. Test report: Remote imagin Would you like to use a 1-metre scope? You can, with this online service that has a focus on planetary photography. FIND US ON FACEBOOK…