Innholdsfortegnelse for November - December 2015 i Australian Sky & Telescope

I remember speaking with an astronomer around 20 years ago, shortly after the first exoplanets had been found. I asked him when he thought we would actually be able to take images of them. I won’t say he scoffed at the idea exactly, but he certainly didn’t sound hopeful, explaining that the difference in brightness between an exoplanet and its host star is so great, and they appear so close together from our vantage point on Earth, that it would be essentially impossible to split them apart. Fast forward to 2015, and it’s no longer looking so unthinkable. Already, nine exoplanets have been imaged, at least in a crude sort of way. And as our article (‘The Next Blue Dot’, p.32) describes, scientists are working on new technologies that hold…

Astronomers have found that a massive filament of gas in the early universe is actually a humongous, galaxy-forming disk of cold gas. One way that galaxies grow — and possibly the predominant way in the early universe — is from cold gas funneled like a pipeline into wells of dark matter. These dark matter wells are dense filaments in the weblike cosmic structure, along which galaxies form. Although computer simulations suggest that many galaxies could have gotten their start as cold-flow-grown disks, observing this accretion in action is difficult because the gas is diffuse and faint. Last year, astronomers detected a large, bright filament of gas called UM 287 shining at us from about 11 billion years ago. It’s fluorescing thanks to the intense ultraviolet radiation of a nearby quasar.…

Looking back over these columns for the last six years or so, a number of things stand out. One is how hard it can be to assign a time or a place or a person to a particular discovery, though I have consistently looked for such a peg to hang each column on. Another is that while some discoveries are totally unexpected, others have been anticipated; the ‘discovery’ is a confirmation of something suspected (‘hypothesised’ to be more technical) to be the case. Then there are the examples of so-called ‘failed experiments ’ missing their first mark but sometimes hitting something else of equal or more value. On December 6, 1958, the US Army launched a space probe called Pioneer 3 (the Army had developed the mission in the days…

In 1990, at the request of Carl Sagan, NASA engineers turned Voyager 1 toward the inner Solar System and commanded its telephoto camera to take a picture of Earth from a distance of 6.5 billion kilometres. This produced the famous ‘pale blue dot’ image of our home planet, which Sagan likened to “a mote of dust suspended in a sunbeam.” With many billions of Sun-like stars in our Milky Way, it’s natural to ask whether there are other ‘blue dots’ like ours — stable, hospitable and teeming with life. The search for Earth-like planets and extraterrestrial life is one of the most fundamental and noble pursuits in all of science. Such a discovery would prove to be a major milestone of our civilisation, on par with the Apollo landings on…

It’s hard for me to believe, but this really is my 200th Binocular Highlight column. To mark the occasion, I’m going to finally answer a question I’ve been asked regularly since column #1: What’s my favourite binocular highlight? It’s tough to choose just one, so I’m going cheat a bit and list a current favourite from each major class of deep-sky object — that way I get six picks. And as it happens, most of my selections are visible in the November evening sky. Galaxy: This is an easy one. For me, M31, the Andromeda Galaxy, is head and shoulders above all others. It’s big, it’s bright and it has two bonus objects: M32 and M110 (see chart below). Open cluster: Another easy one. M45, the Pleiades, is not only…

Most Exploring the Moon columns describe a single type of lunar landform, such as basin rims, crater floors, rilles or mare ridges. Yet when looking through a telescope’s eyepiece, you don’t see just one feature in isolation but rather everything in that portion of the Moon. The fun then comes in deciphering which processes created the different landforms you see — and in what sequence. In fact, this is the stratigraphic approach that legendary astrogeologist Eugene Shoemaker and his colleagues developed in the late 1950s, when modern mapping of the Moon began in preparation for the Apollo landings. Stratigraphy is based on the law of superposition, namely, the rock units on top must be younger than the ones below. For example, sometimes craters sit atop other features and therefore are…

The perfect beginner’s telescope. What does it look like? How much should it cost? Telescope manufacturers have wrestled mightily with these questions for years. Aim for a very low price point and you end up with the much (and rightly) maligned department-store trash scope. Or, produce something with a host of quality features and watch customers blanch at the price, then rush to the shopping centre to buy a trash scope. The sweet spot can be elusive. And yet, many manufacturers do offer decent starter telescopes at reasonable prices. Could the Vixen telescope featured here be one of them? The Vixen package in this review comprises two components: the R130Sf 12.7-cm, f/5 optical tube assembly (OTA), and the Porta II altazimuth mount. (Either can be purchased separately.) The OTA is…

November 2005 Inflationary universe In January 1980, a young physicist named Alan Guth unveiled a brilliant idea that had just one drawback: it didn’t work. Fully aware of this shortcoming, he was convinced of the idea’s importance. History shows his faith to have been well placed. The idea, called ‘inflation,’ was not discarded. Instead, the notion of an explosive growth spurt in the universe’s earliest moments has become a cornerstone of cosmology. Astrophysicist Michael Turner calls it “the most important idea in cosmology since the Big Bang”. November 2010 NASA’s quiet achiever NASA’s Mars Reconnaissance Orbiter carries three cameras, two spectrometers, a radar mapper and a pair of radio-science experiments. As of June 2010, MRO’s primary camera had made 16,077 observations and returned 13.4 trillion pixels of digital imagery. Perhaps…

Researchers have confirmed that three white dwarf stars went supernova in intergalactic space. The space between galaxies is not entirely empty. Sometimes observers come across stars that have been ejected from their hosts and left to drift alone. Although solitary, they’re still important for understanding how much mass the universe contains and where that mass is. But it’s difficult to see individual stars in the distant universe. So astronomers turn to supernovae, which are easier to spot. In 2011, researchers conducted a survey of 23 exploding white dwarfs in and near distant galaxy clusters. They discovered four of them were in the space between galaxies. But they couldn’t resolve the images clearly enough to confirm that the white dwarfs truly floated in solitude. Now, using Hubble images, Melissa Graham (University…

Soccer-ball-shaped molecules lurking in the dusty corners of the Milky Way explain part of a spectral mystery, Ewen Campbell (University of Basel, Switzerland) and colleagues report in the journal Nature. Diffuse interstellar bands (DIBs) have haunted astronomers for almost a century. First discovered in 1922, these spectral absorption lines (more than 400 of them) are seen any time astronomers look toward dust-reddened stars. But no ions or molecules tested in the lab have provided a good spectral match. Campbell’s team decided to test ionised buckminsterfullerene molecules (a.k.a. ‘buckyballs’) to see if they might explain some of the bands. Buckyballs link 60 carbon atoms into a stable, quasi-spherical cage. Astronomers have already detected them in space in gaseous and solid forms, but neutral buckyballs don’t absorb light at the right wavelengths…

The largest solar flare in modern history happened only 12 years ago. On November 4, 2003, a sunspot group on the western limb of the Sun hurtled a massive blast of particles in a direction away from Earth. A week before, the same sunspot group had cranked out eruptions that spawned aurorae here on Earth. This flare was likely as big as the first one ever recorded, using ink and paper, in 1859. But both these eruptions, monsters by our standards, are tiny compared with superflares — flares roughly tens to thousands of times more energetic than the largest solar flare ever observed. In fact, many yellow, middling-mass G-type stars just like the Sun produce superflares. Astronomers wonder why this is. And they’re beginning to ask: Could a superflare ever…

Even though its launch is still years away, astronomers are already looking beyond the James Webb Space Telescope for the kind of space-based observatory that could truly revolutionise astronomical research in the future. A recent study sketches out the rationale for a gigantic High-Definition Space Telescope (HDST) that could undertake this quest. Its mirror would be at least 12 metres across. According to the report, issued by the Association of Universities for Research in Astronomy, this mega-telescope and its coronagraph would search for planets around the roughly 600 stars that lie within 100 light-years of Earth and conduct spectroscopic scans for signs of life on or around them. The HDST would also make extraordinary breakthroughs in the study of black holes, dark energy, and cosmic evolution. Learn more at hdstvision.org.…

Avast section of the November evening sky is filled with dim water-related constellations. The faintest of them all is Pisces, ‘the Fish’. Even so, I write in praise of Pisces. I’m going to explain why even its dimness can be part of the pleasure we find in observing it. But there’s much else of mental interest to ponder, and visual interest to observe, in this constellation of the (two) Fish. How easy is it to see anything in Pisces with the naked eye if you have a heavily light-polluted sky? Not very. The only two stars brighter than magnitude 4.0 in the constellation are Eta (›) and Gamma (›) Piscium (magnitude 3.6 and 3.7, respectively). Fortunately, that’s not all there is to the story of observing Pisces. For instance, there…

Mars is still just a tiny dot in the pre-dawn sky, swelling to around 5" wide in November. But get ready for bigger things. That little spark, currently overwhelmed by Venus and Jupiter nearby, is beginning its best apparition since 2005. Mars will spend next May and June closer and larger than it has been since when you were 10 years younger, topping out at 18.6". It will be at opposition on May 22, 2016 and closest to Earth on May 30. If you’ve never seen Mars well, this will be your chance. And the good news for southern observers, of course, is that Mars will spend those months near the head of Scorpius at a declination of around –21°. As a bonus Saturn will be shining in the same…

For decades, astrophotography gurus advised newcomers to start with simple camera-on-tripod shots before graduating to the advanced task of shooting celestial targets through telescopes. This was meant to teach the limits of normal photographic techniques; targets in the night sky are almost always faint and require long exposures to record adequately. But without tracking to counteract Earth’s rotation, you were limited to only a few seconds or so before trailing compromised your shot. Next, you’d get a tracking mount and continue from there. What those guides didn’t account for is the power and simplicity of digital single-lens reflex (DSLR) cameras. These have enabled astrophotographers to discover the beauty of nightscape photography as a unique pursuit in itself. Now many devote all their nights — indeed their careers — to shooting…

Comets are rare visitors to our night sky. Often arriving with little warning, they put on a brief show and then slowly fade as they recede from the Sun. The brighter ones grab the public’s attention, while amateurs grab their cameras. A bright comet is easy to shoot — simply point your camera or telescope at it, open the shutter for about five minutes, and you’re pretty much done. Imaging the fainter ones can present an interesting challenge; they require much longer exposures to reveal any streaming ion or dust tails, which leads to more complex issues when assembling your image. Perhaps the most appealing images of comets portray them as a brilliant greenish coma with a long, streaming tail that trails away against a field of sharp, round stars.…

Snake Valley Astro Camp November 6-8, 2015 Snake Valley, Vic Phone: 03 5231 3048 VicSouth Desert Spring Star Party November 6-9, 2015 Annual star party hosted by the astro societies of Victoria and South Australia vicsouth.info National Australian Convention of Amateur Astronomers March 25-28, 2016 Held every second year, the NACAA is Australia’s premier get-together for amateur astronomers to discuss research projects and the latest technologies. In 2016 it will be hosted by the Sutherland Astronomical Society in Sydney. nacaa.org.au Royal Astronomical Society of NZ Conference May 2016 Annual meeting of New Zealand’s astronomers hbastrosoc.org.nz/rasnz-conference-2016/ South Pacific Star Party May 5-8, 2016 Annual star party hosted by the Astronomical Society of NSW asnsw.com/spsp Queensland Astrofest August 2016 Lions Camp Duckadang, Linville, Queensland Long-running annual star party www.qldastrofest.org.au National Science Week…

SCIENTISTS SPOT FIVE-STAR SYSTEM A rare four-star system turns out to have a fifth wheel, Marcus Lohr (The Open University, UK) and colleagues report in the journal Astronomy & Astrophysics. Although multiple-star systems are common, those with more than three stars are rare. In 2013 Lohr’s team discovered the quadruple system 1SWASP J093010.78+533859.5. It has two eclipsing binaries, the pairs separated from each other by 21 billion km. The fifth star revealed itself when the team took spectra to study the stars in more detail. The system is 9 to 10 billion years old. • ANNE MCGOVERN AURORA ON A DWARF STAR Astronomers have detected auroral emission on a star. Ultra-cool dwarfs (UCDs) are the runts of the stellar family: they include both the least massive stars and brown dwarfs.…

Astronomers have discovered an exploding star that tops the ‘superluminous’ charts. Dubbed ASASSN-15lh, the magnitude-17 supernova was found as part of the All-Sky Automated Survey for Supernovae (ASAS-SN). Follow-up observations suggest it shines with the luminosity of 572 billion Suns, and spectra confirm its bluish light has been travelling toward Earth for the past 2.8 billion years (redshift of 0.2326). The debris lacks hydrogen emission lines, meaning the star lost its outer layers prior to exploding.…

As spring settles in, Orion once more begins its journey into our night skies. Its dominant stars give shape to the night: red and supernova-ready Betelgeuse; blue giant Bellatrix; the blue-white supergiant that dominates the Rigel triple-star system; and windy supergiant Saiph. And tucked within this most recognisable of constellations is the Orion Nebula, the nearest birthplace of massive stars — those with more than eight times the mass of the Sun. Yet massive stars’ visibility from Earth is deceiving; they are actually few and far between, making up fewer than 1% of all stars in the Milky Way. In part, this is because the behemoths live their lives fast and furious, running out of fuel and blowing up into giants before lower-mass stars even start fusing hydrogen in their…

November will see comet C/2013 US10 (Catalina) reaching perihelion (closest point to the Sun) at 0.82 a.u. on the 15th, however it will be too close to the Sun to observe throughout the month. There is little chance of seeing it again until the end of the first week of December when it might be possible to pick it up visually low in the morning twilight in the constellation Virgo. Throughout December, the comet will move slowly northward, crossing into Bootes by the end of the year. Unfortunately, it will remain very low in the dawn sky, although its brightness is expected to stay fairly constant between magnitude 6.5 and 7 as its increasing distance fro m the Sun is matched by decreasing distance from Earth. Unless a bright new…

When working through the Herschel 2500 list of deep-sky objects discovered by William Herschel between 1783 and 1802, the observer occasionally experiences a pleasant surprise, such as an extreme edge-on galaxy or a tight clump of galaxies. The H2500 is a project that has kept me employed for years and always provides an answer to the perennial question: “What new object can I see tonight?” The question took on new meaning after my recent cataract surgery. Once or twice a year I come upon a very pleasing field of galaxies that I want to share with other observers. In the 50› field surrounding 1 Arietis there are five NGC galaxies, most or all of them associated members of the NGC 697 group. Together with four fainter galaxies and the three…

I’ve always had great admiration for telescope makers who not only craft fine optics, but also have the talent to come up with new designs. Many of us can grind a decent mirror for a Newtonian reflector but couldn’t even begin to concoct a new optical system. Similarly, there are computer jockeys who can crank out interesting telescope recipes but have never actually pushed glass — and a design isn’t a telescope until it’s built. Jim Stilburn is one of the few who can do both very well. Jim’s previous effort, a 15-cm corrected Dall-Kirkham, was the inspiration for his newest creation, a 25-cm f/5 hyperbolic reflector. He says the 15-cm scope “provided tantalising views… but it was only a matter of time before I came down with aperture fever.”…