Innholdsfortegnelse for February - March 2015 i Australian Sky & Telescope

It's great to back in the editor's hot seat at Australian Sky & Telescope, 10 years after we launched the magazine. So much has changed during that decade, but one thing has stayed the same — the flood of amazing discoveries and insights into our cosmos just keeps getting stronger as each year goes by. New telescope technologies and huge computing power are enabling astronomers to tackle research problems they could only have dreamed about in decades past. We’re truly experiencing a golden age discovery. For all that new technology, though, there are always challenges to solve. As our cover story illustrates, as telescopes grow in size and complexity, so too does the potential for things to go wrong. Today’s telescopes are huge enough, but tomorrow’s behemoths — such as…

Observations from several radio telescopes confirm that, when two galaxies merge, their progeny often have extended gaseous disks. Simulations from the 1970s suggested that, when two big disk-shaped galaxies merged, theyd create a big elliptical galaxy, a fairly featureless spheroid of stars. But about a decade ago, better simulations by several teams showed that, if the disk galaxies have a lot of gas, the object their merger creates will also be a disk galaxy, with spiral arms or maybe even a central bar. Junko Ueda (National Astronomical Observatory of Japan) and colleagues have now confirmed this prediction with observations, published in the September Astrophysical Journal Supplement. The team looked at emission from cold molecular gas from 37 merger-created galaxies, using both new and archival data. Of the 37 galaxies, the…

Two spacesuited figures walk across a rocky plain surrounded by steep hills in the orange light of the late afternoon. Trundling behind them is an eight-wheeled robot. Overhead a small quadcopter streams video back to a field operations centre in a nearby vehicle, from where the robot and astronaut operations are being co-ordinated. This is not a scene from a science fiction movie, or even a NASA conceptualisation of future interplanetary explorers. Instead, it was a trial carried out during the Mars Society Australia’s Mars Robot Challenge Expedition near Arkaroola, 700 kilometres north of Adelaide in South Australia's Flinders Ranges. The July 2014 expedition comprised 30 people, a mixture of engineering and geological researchers, science and engineering graduate and undergraduate students from Australia and India, plus volunteers, accompanied by seven…

The Hubble Space Telescope, which will celebrate its 25th anniversary in April 2015, is the symbol of our era for every astronomer. Orbiting above the distorting effects of Earth’s atmosphere, it has provided unprecedented views of star clusters, nebulae and galaxies. Using its suite of sensitive cameras and detectors, and focusing on ‘blank’ patches of sky, Hubble has also revealed the building blocks of galaxies so far away that their light took many billions of years to reach us. But cosmologists want to reach even farther. And since they can’t swap Hubble’s 2.4-metre mirror for a larger one, they’re now seeking assistance from nature’s own zoom lenses. Using the gravitational-lensing effects of six remote clusters of galaxies, the new Frontier Fields program aims to push back Hubble’s limits and study…

University of Tokyo Atacama Observatory (TAO) Elevation: 5,640 m Location: Atacama Desert, Chile Chacaltaya Astrophysical Observatory Elevation: 17,160 ft (some gear at 17,600 ft) Location: Andes, Bolivia James Ax Observatory – Polarbear Elevation: 5,190 m Location: Atacama Desert, Chile Atacama Cosmology Telescope (ACT) Elevation: 5,190 m Location: Atacama Desert, Chile Shiquanhe Observatory Elevation: 5,090 m Location: Ngari Plateau, Tibet Chajnantor Observatory – ALMA, APEX, QUIET, et al. Elevation: 5,090 m Location: Atacama Desert, Chile Chajnantor Observatory – ASTE, NANTEN2 Elevation: 4,800 m Location: Atacama Desert, Chile Large Millimetre Telescope Alfonso Serrano (LMT) Elevation: 4,580 m Location: Sierra Negra, Puebla, Mexico Indian Astronomical Observatory Elevation: 4,500 m Location: Mount Saraswati, Ladakh, India Meyer-Womble Observatory Elevation: 4,312 m Location: Colorado, United States Yangbajing International Cosmic-ray Observatory Elevation: 4,300 m Location: Yangbajain, Tibet…

When you look up, which constellation do you think is the most spectacular in the sky? Orion, most amateur astronomers would no doubt say. But Id go even further. In my opinion, no other constellation comes close to equaling the visual impact of Orion. Why is that? Let me review some of the reasons Orion virtually brands our minds with its stunning starfire. The brightness. Skywatchers often consider Orion the brightest constellation, even though Scorpius stands as winter's brightest for many observers. Mighty Scorpius does include an impressive number of stars brighter than magnitude 2.5, and an even more impressive number brighter than 3.0. But it has only one 1st-magnitude star, Antares, which is always dimmer than Orion’s Rigel, and almost always dimmer than Orion’s variable Betelgeuse. For those of…

For telescopic observers, Jupiter’s satellite Io is hardly a showpiece object. Although 5% larger than the Moon, Io is 2,000x more distant and, under optimal conditions, can barely be distinguished as a non-stellar disC through a 5-inch telescope. Observing Io is like observing a coin from a distance of almost 5 kilometres. For more than a century, Io has been the subject of a number of observing conundrums — a number that is out of all proportion to its diminutive apparent size. In his popular 1954 book Guide to the Planets, Patrick Moore wrote: “Io sometimes shows peculiar fluctuations in brilliancy, and I once saw it brighten up strikingly in the space of a few hours for no apparent reason” In 1964 astronomers Alan Binder and Dale Cruikshank reported that…

Binocular telescopes are one of those ideas that sound great, yet rarely seem to work out in practice. Everyone appreciates the rewards of astronomy with regular binoculars, so it’s easy to imagine how amazing it would be to scale up the aperture and magnification. And yet, binocular telescopes remain rare novelties. That’s because they’re not easy to make, and the difficulty runs deeper than the work involved in making twin optical tube assemblies. But telescope-maker Jerry Oltion was up for the challenge. “I decided early on to go for simple and strong ” he says. That approach led him to ‘think inside the box ’ The optics reside in two boxes, one housing two 12.5-inch-diameter, f/4.7 primary mirrors, the other supporting dual upper-cage assemblies. One of the most challenging aspects…

Like the icy worlds of the outer Solar System, Antarctica also has isolated subsurface bodies of liquid water completely cut off from sunlight. Since these lakes were first identified in the 1990s, scientists wondered if they harbored life. As reported in the August 21 issue of Nature, the answer is a definite yes. After careful preparations to avoid contamination, an international, multidisciplinary team including Brent Christner (Louisiana State University) and John Priscu (Montana State University) used a hot-water drill to bore down into Lake Whillans, a small body of water about 800 metres below the surface. The team brought up 30 litres of water. Early analysis reveals 130,000 living cells per millilitre of lake water, a density roughly equivalent to that of deep oceans. Amazingly, the team has identified at…

Two studies suggest that some of the ultraluminous X-ray sources (ULXs) thought to be beefy black holes are created by much less massive objects. ULXs spew out X-rays at luminosities roughly a trillion times the Sun’s X-ray luminosity. The standard explanation for a ULX is that the X-rays come from extremely hot material that a black hole has pulled from a companion star. The more massive the black hole, the brighter its accretion disk can be. But ULXs are uncomfortably bright: to explain them, a stellar-mass black hole would need to reach or surpass its maximum gas-gobbling rate, called the Eddington limit. That might be possible due to ‘force-feeding’ that can occur under certain conditions. Or these sources might be intermediate-mass black holes (IMBHs), theoretical objects with masses of hundreds…

February 2005 Uranus Kicks Up A Storm Many astronomy enthusiasts had a hard time getting excited about Uranus after Voyager 2's 1986 flyby. Unenhanced imags of the planet showed a featureless aquamarine ball — in stark contrast to Jupiter's and Saturn's richly detailed belts and storms. But recent near-infrared images from the 10-metre Keck II telescope in Hawaii demonstrate that first impressions can be deceiving. The images, taken in 2003 and 2004 with adaptive optics to counter atmospheric blurring, revealed dozens of discrete clouds, more than the total seen in all previous observations up to 2000. The clouds vary in size, brightness and longevity, proving that Uranus (like Neptune) has a dynamic and complex atmosphere after all… The major reason for Uranus' new-found dynamism is probably its extreme seasonal cycle.…

Edmond Halley, who flourished around the start of the 18th century, had many remarkable achievements. Among them was the first detailed study of the ‘variation of the compass’ (the difference between true north and magnetic north) up and down the Atlantic Ocean, undertaken to find a method of measuring longitude; his proposal that we could use the transits of Venus to determine the distance between the Earth and the Sun; and his encouragement of Isaac Newton to prepare for publication his epoch-making book the Principia, which Halley also paid for. But for most people Halley’s name is associated principally with ‘his’ comet. Halley’s is the best-known of the comets, uniquely combining brightness (bright enough at times to be seen in the daytime) with regular and not too infrequent appearances (every…

The clement cloak of gas that enshrouds Earth is truly a wonder. The composition of our planet’s unique atmosphere arises in part from a harmony of respiration and photosynthesis, performed by the organisms it shields from the deadly radiation and cold of space. Yet we skywatchers could be forgiven for harboring mixed feelings about this atmosphere. For the layers of gas above our heads distort the path of incoming light from space. That’s because the atmosphere is far from uniform. For example, adjacent air pockets can exhibit markedly different densities and turbulent motions. The overall consequence is that incoming light rays get refracted along a multitude of ever-changing pathways, as residual heat drives convection that ceaselessly churns up the nocturnal atmosphere. Worse still, highly magnified images only serve to exaggerate…

Go hiking in the Rockies or shuffle between its ski lifts and you’ll soon have to stop and catch your breath. Air pressure drops quickly as you ascend into the atmosphere (initially by 33 millibars per 330 metres gained), so that each breath you draw harvests fewer oxygen molecules for your lungs. You might not feel the reduction in pressure but, as you climb, packets of plastic-wrapped food expand to bursting and bottles hiss when opened as they exhale compacted air. Rise beyond 3,000 metres and your breathing becomes markedly faster. Your bloodstream’s oxygen level drops and your rest pulse races as high as 100 beats per minute in an effort to compensate. You’ll likely experience fatigue, headache, reduced appetite, or perhaps difficulty sleeping at night due to irregular breathing.…

This is the third time I've written about doubles in Puppis, a constellation with hundreds of them accessible to mid-size amateur telescopes (say, 20- to 25-cm). Puppis is part of the gigantic, now-defunct constellation Argo Navis; in sky area Puppis is slightly larger than Orion. We'll begin with 3rd-magnitude Pi Pup, a triple star and a useful guide star. This is a James Dunlop double, DUN 43, very wide with magnitude 3 and 8 stars, best seen at low power and showing colour contrast of orange and blue-white. It's located in a loose cluster, Cr 135; my best view was with a 10x70 finder, which showed the cluster nicely as well as Dunlop's companion to Pi. Those with larger scopes might like to attempt HDS 1008, the bright star of…

When you walk outside and look to the northeast on these fine late summer, early autumn evenings, the first constellation that catches your eye is mighty Orion. If you want to swing the telescope over to M42 for a quick look, be my guest. The Great Nebula is always a marvel, but tonight we’re after less familiar quarry. Let’s begin our evening’s journey in Monoceros, the Unicorn, Orion’s neighbouring constellation to the east. A computer-controlled Go To telescope will stand you in good stead when touring this constellation for, despite its evocative name, the Unicorn is dim, with its most prominent star, Beta (в) Monocerotis, shining weakly in the backyard sky at magnitude 3.8. If there’s a deep-sky object that spells the warmer months for me other than the Orion…

The art of deep-sky astrophotography differs from most other types of picture-making. Astro-imagers learn the fundamental techniques of combining many long exposures to suppress noise while simultaneously increasing the signal to reveal ever-fainter objects in their images. Tools such as calibration frames, pixel rejection methods, and tri-colour technique are mostly unheard of in other types of photography. But many fundamentals of photography remain the same whether your subject is a distant galaxy or a picturesque landscape. Colour balance, contrast, and composition come into play in every great image, no matter the subject. As imagers strive to raise their work beyond the point of simple picture-taking, composition and visual aesthetics become important considerations in the journey to create a truly memorable photograph. Here are some ways to consider your next target…

Citizen Scientists Probe Early Galaxies. Data collected by Galaxy Zoo volunteers show galaxies form barred structures much earlier in cosmic history than previously thought. Previous observations have shown that the fraction of barred galaxies dropped from 50–70% in the nearby universe to 10% when the universe was only 6 billion years old. But as Brooke Simmons (Oxford, U.K.) and colleagues report in an upcoming Monthly Notices of the Royal Astronomical Society, extending the data back to when the universe was only 3 billion years old shows that the number of barred galaxies was still as high as 10%, and not the expected zero. These early galaxies might have formed either because their contents settled down earlier than thought would happen, or because they were formed by two galaxies colliding. SHANNON…

Last year, the world’s astronomers watched a mysterious, gaseous object called G2 slingshot around the supermassive black hole at the centre of the Milky Way. Astronomers first spotted G2 in 2011, and its crazy orbit immediately sparked debate: G2 makes a beeline for the black hole, whips around it, and shoots straight back out again. To do so, the object must have somehow lost enough angular momentum that, instead of following a more circular orbit, it started to fall headlong toward the black hole, called Sagittarius A* (pronounced "A star"). The answer to the mystery is twisted up in G2’s nature: is it merely a gas cloud, or does it hide a star inside? The hope was that G2 would reveal its nature during its close encounter with Sgr A*…

WA Astrofest March 28 Biennial Victorian astronomy conference, hosted in 2015 by the Bendigo Astronomical Society caastro.org/Astrofest VASTROC April 17-19 Biennial Victorian astronomy conference, hosted in 2015 by the Bendigo Astronomical Society vastroc.net Royal Astronomical Society of NZ Conference May 8-10 Annual meeting of New Zealand's astronomers rasnz.org.nz/Conference/ Trans-Tasman Symposium on Occultations May 11 Australasian get-together for occultation observers, this year to be held in Lake Tekapo, NZ occultations.org.nz South Pacific Star Party May 14-17 Annual star party hosted by the Astronomical Society of NSW asnsw.com/spsp CWAS Astrofest July 18-19 Annual conference held in Parkes (home of 'the Dish'), including the David Malin Awards cwas.org.au/Astrofest/ Queensland Astrofest August 7-16 Annual star party qldastrofest.org.au National Science Week August 15-23 Lots of public astronomy activities held around Australia scienceweek.net WHAT’S GOING ON?…

Jupiter's icy moon Europa is seen in brilliant detail in this newly reprocessed picture made from images taken by the Galileo spacecraft in the 1990s. Europa featured in Arthur C. Clarke's 2010: Odyssey Two (the sequel to 2001: A Space Odyssey ), in which a message was sent to Earth: "All these worlds are yours except Europa... attempt no landing there". As the late Clarke was right about so many other things, perhaps we should take this warning seriously. NASA/JPL-CALTECH/SETI INSTITUTE…

For the last two decades the world’s astronomers have been tantalised by the construction of one new record-breaking, ground-based behemoth telescope after another. Each was heralded as the telescope of the future, able to outperform the Hubble Space Telescope, peer into the distant past to solve the mysteries of dark matter and dark energy, and reveal the puzzles of stellar evolution and the formation of planetary systems. Yet, as each one neared completion, the publicity and news coverage would slowly peter out. Years would pass without any game-changing scientific discoveries coming from these leviathans. What had happened? We decided to find out, and what we have learned is that these telescopes are far more difficult to build than their press releases have suggested. “These are huge industrial machines” explains Gerard…

Infrared astronomy from the ground is hampered by absorption by compounds in Earth’s atmosphere, particularly water vapour. The suitability of an observing site, particularly those tuning to submillimetre wavelengths, is often gauged from its Precipitable Water Vapor (PWV) value, the depth of liquid that would be obtained if all the gaseous water along the line of sight to the zenith could be condensed. PWV decreases with elevation and is sometimes less than 1 mm above the summit of Mauna Kea.…

Binocular observers tend to work with the same deep-sky catalogues as telescope users, so it’s no surprise that the biggest and brightest Messiers and NGCs are also the best known binocular targets. Yet there are some objects that look great through binos, but don’t appear on these popular lists. For example, consider the Alpha Persei Association, also known as Melotte 20. Although the terms ‘star cluster’ and ‘stellar association’ are often used interchangeably, there is a subtle difference between them. Both are groups of stars that formed in the same place at the same time, but members of an association aren’t gravitationally bound to one another. Or to put it another way, a star cluster can become an association (thanks to orbital dynamics, stars in older clusters tend to drift…

Unless a bright new comet is found in the meantime, February and March hold little promise for comet observers using small telescopes. At the time of writing in late October, only two objects hold any prospect at all of being visible. Even these will not be easy and, from mid-southern latitudes, confined to the very start of the period. The best prospect is C/2014 Q2 (Lovejoy), which may still be found in evening twilight low in the northwest for the first few days of February. Having passed perihelion on January 30 at a distance of 1.29 au from the Sun, the comet is moving northward through Andromeda and will soon be lost to southern observers. According to brightness estimates late last October, it may still be as bright as magnitude…

At the November 15, 1754 meeting of the Academie Royale des Sciences, Nicolas-Louis de Lacaille presented a report of his scientific expedition to the Cape of Good Hope and a beautiful map of the southern skies painted by his friend Anne-Louise Le Jeuneux. Now displayed in the Paris Observatory’s Grande Galerie, this chart boasts several constellations devised by Lacaille, including Fornax, which represents a chemist’s furnace. The Furnace burns in a part of the sky that's familiar to southern skygazers, and is even visible to many of our cousins in the Northern Hemisphere. Its treasures are assuredly worth no matter where you live. Fornax is largely populated with galaxies, but it also holds one large, impressive planetary nebula. NGC 1360 bedecks the northeastern corner of the constellation, and the stars…

You can’t do anything about sky glow, but you can do something about ambient light. Light from nearby sources prevents your eyes from attaining as much dark adaptation as possible. Turn off any lights you can and shield your eyes. I drape a piece of dark cloth over my head when I’m at the eyepiece. Many deep-sky observers use too little rather than too much magnification. Most objects are small to medium-sized targets, and magnifications of 100› and above will show more detail and spread out the background sky glow. Wait for special nights. If you’re after a particularly difficult object, look for it after a weather front has passed through, when the sky is at its cleanest and driest. Wait for special times. If you’re having trouble with a…

There aren’t many fields like astrobiology. In the past I’ve even heard it called the science without anything to study. But the future has always been its strength; success in astrobiology would revolutionise our perspective on the nature of the cosmos, making Copernicus’ decentralisation of Earth seem like a prehistoric rite of passage. A critical task for astrobiology is not just finding life elsewhere, it’s finding life that’s truly independent of terrestrial life. For example, if we find extant or extinct organisms on Mars, there’s a good chance they’ll be related to life on Earth — part of a genetic diaspora from microbe-laden planetary material thrown around the Solar System by 4 billion years of asteroid impacts. Either the Martians will be Earthlings or the Earthlings will be Martians. This…

As Robert Heinlein used to say. “There ain’t no such thing as a free lunch” That’s usually true, but I almost feel like I got a free meal with Celestron’s Edge 800 Schmidt-Cassegrain Telescope and VX mount. I found the combination of the advanced 20-cm SCT and inexpensive German equatorial mount (GEM) surprisingly capable, especially when equipped with Celestron’s Edge f/7 reducer, off-axis guider, and StarSense auto-alignment system. I have dreamed of an enormous SCT on a fork mount to ease me into my golden years. Unfortunately, I have to carry my scope to dark sites to do my best observing, and I really didn’t want to haul a 35- or 40-cm telescope around. The more I thought about it, the more convinced I became that an 20-cm SCT was…