Innholdsfortegnelse for January 2019 i Australian Sky & Telescope

SCIENTISTS ATTEMPTED TO predict the shape of the Sun’s corona as it would appear during the total solar eclipse on August 21, 2017. Observations confirmed that they got the broad strokes right. The corona, an intricate crown of thin, super-hot plasma around the Sun, expresses our star’s hidden magnetic angst. Its charged particles respond to the magnetic field by twisting into loops, bands, and even erupting into interplanetary space. Solar physicists led by Zoran Mikić (Predictive Science) report August 27 in Nature Astronomy that they can accurately predict the appearance of the corona one week in advance — an important milestone on the path to predicting the oncoming solar wind. The team offered a new model of the Sun’s outer layers that takes into account how their heat and magnetic…

BEFORE THE SPACE AGE, it was common to regard Venus as a planet stuck in a state resembling Earth’s deep past — perhaps a carboniferous swamp world with tree ferns and giant reptiles. Now we know that our nearest planetary neighbour is actually a vision of our likely future. When Venus and Earth were both young, their surface conditions were probably very similar, sporting warm, organics-rich oceans and active geology. They were the kind of places where we think life could easily have formed, if our current understanding of both the origin of life and of Venus are correct. Yet the Sun gradually brightens as it ages, causing the inner edge of the habitable zone, where surface water can exist on rocky planets, to slide inexorably outward. Some time in…

In the winter, we look galactically inward, toward the inner arms and core of the Milky Way. Like someone lying down in a paddock and gazing at distant mountains, we see first the closest stars and clusters (the grass), then the more distant stars, clusters and nebulae that define the inner spiral arms (the trees), and finally the galaxy’s vast central bulge looming in the distance (the mountains). In the summer, we look in the opposite direction, outward toward the edge of the galaxy. The galaxy has only one centre, but for every observer it also has an anticentre, the point 180° around the sky from the galactic core. For us, that point lies in the constellation Auriga, the Charioteer. No bright star marks this galactic antipode, but it’s easy…

WHITE DWARFS ARE EXTREME — so dense that a single spoonful weighs tonnes. These tiny dying suns are the prime movers behind a newfound phenomenon that features another extreme: the fastest stars ever seen fleeing the Milky Way. The key to the drama is the white dwarf’s minuscule size, only about 1% the diameter of the Sun, or about as small as Earth. Another star can therefore orbit just a few thousand kilometres from the white dwarf’s centre, whizzing around it much faster than a distant companion would, for the same reason that Mercury moves much faster than Pluto. In such a close orbit, the white dwarf can steal gas from its mate and gain enough mass to annihilate itself in a Type Ia supernova. Then the companion dashes away…

WHAT AMATEUR ASTRONOMER hasn’t fantasised about operating a large telescope in an extremely dark location that regularly experiences good seeing conditions? While many of us may have had glimpses through large instruments at star parties or at observatory public nights, being able to image through one has been mostly a dream… until now. Operating telescopes remotely isn’t new. There are several telescope-hosting facilities at sites in Australia, Africa, North America and South America, where individuals with the means can lease a spot at a ‘telescope farm’ for their equipment and image remotely. Some facilities also have scopes that users can rent to take dazzling deep sky photos or perform extended research. But one type of astrophotography has remained impractical for imagers, until now: planetary imaging. Chilescope A group of intrepid…

Just as stargazers at mid-northern latitudes are unable to see the Southern Cross because it never rises above their southern horizon, so for much of Australia it is not possible to trace the outline of the seven main stars (the ‘Big Dipper’) of the constellation Ursa Major (the ‘Great Bear’). But from the northern parts of Queensland, the Northern Territory and Western Australia, these stars do rise well above the horizon. In Brisbane where I live, even with refraction assisting, Dubhe (Alpha Ursae Majoris), the northernmost star of the grouping, transits at a mere 1.2 degrees altitude. But drive a few hours’ north to Noosa Heads, and from the north-facing beach it transits at nearly 2.2 degrees altitude. This location a little over one degree of latitude north of Brisbane…

Parker Probe’s first perihelion NASA’s Parker Solar Probe spacecraft flew to within 24 million kilometres of the Sun’s photosphere during its fly-by on November 6, Australian time. The event marked the mission’s first-of-several perihelion passages, as the spacecraft begins its orbits of the Sun. At this perihelion, the craft had to endure intense solar radiation and plasma at temperatures of 2 million degrees Celsius. • JONATHAN NALLY Impact shaped ice giant Scientists have long known that a long-ago impact likely caused Uranus’s strange tilt. Jacob Kegerreis (Durham University, UK) and colleagues explored this concept further by simulating more than 50 impact scenarios. In the July 1 issue of Astrophysical Journal, the team concludes that 4 billion years ago, a rock-and-ice protoplanet with at least twice Earth’s mass collided with Uranus…

Once again the Auckland Astronomical Society’s annual Harry Williams Astrophotography Competition drew an outstanding range of entries from across New Zealand. Our congratulations go to all of the worthy winners and runner-ups shown on these pages. Australian Sky & Telescope is proud to be a sponsor of the competition.…

Giuseppe ‘Bepi’ Colombo (1920–84) was an Italian mathematician and engineer who discovered that the time it takes Mercury to rotate around its axis is two-thirds as long as its year. Before his work, astronomers had thought the planet’s day was the same length as its year, 88 days. He also proposed putting NASA’s Mariner 10 spacecraft in a 176-day-long solar orbit that would bring it past Mercury repeatedly, enabling the mission’s three flybys.…

THIRTY METER TELESCOPE (TMT) 1. WFOS (Wide Field Optical Spectrometer) Near-ultraviolet and optical wide-field multi-object imager and spectrograph Wavelength range: 0.31 – 1 μm Field of view: ~10 arcmin diameter 2. IRIS (Infrared Imaging Spectrometer) Near-infrared adaptive optics-fed integral field imager and spectrograph Wavelength range: 0.8 – 2.5 μm Field of view: 32 × 32 arcsec (imager) EXTREMELY LARGE TELESCOPE (ELT) 1. MICADO (Multi-AO Imaging Camera for Deep Observations) Near-infrared adaptive optics-fed imaging camera and spectrograph Wavelength range: 0.8 – 2.4 μm Field of view: 50.5 arcsec × 50.5 arcsec 2. HARMONI (High Angular Resolution Monolithic Optical and Near-infrared Integral Field Spectrograph) Near-infrared integral-field spectrograph Wavelength range: 0.47 – 2.45 μm 3. METIS (Mid-Infrared ELT Imager and Spectrograph) Mid-infrared imager (with coronagraphic capability)…

The SEIS seismometer’s sensors reside inside a vacuum chamber with a self-levelling, three-legged platform. Those sensors must operate in vacuum in order to be sensitive enough to detect ground motions as small as 2.5 × 10-11 m — about half the Bohr radius of a hydrogen atom. But in 2015, the vacuum chamber developed a leak during testing, and CNES was unable to repair the leak in time for Insight’s planned launch in March 2016. NASA considered canceling Insight entirely, since a launch delay would mean a two-year postponement that would cause the mission’s cost to greatly exceed its relatively economical US$425 million budget (excluding launch services). Early in 2016, NASA managers announced that Insight would proceed— but that work on a brand-new design for a vacuum enclosure would switch…

Although its name means cold, we only see Mare Frigoris when illuminated by sunlight and therefore when it is quite hot. In fact, we see Frigoris so often because it stretches about 1,600 km between the crater Atlas near the Moon’s northeastern limb and Sinus Roris along the northwestern limb. You can spot some part of Mare Frigoris typically every night between day 4 and 12 of each lunation. Its ease of visibility, however, is not matched by an easy understanding of why it has such an elongated shape, like an eyebrow over Mare Imbrium. Most large maria appear to be roughly circular because they fill the circular depressions of impact basins. This is most readily seen at Mare Crisium, where the basin’s surrounding rim is nearly continuous. Similarly, the…

I CONFESS I’m a sucker for ball mounts. Isaac Newton mounted his very first telescope on a ball, and so did I. I’ve loved the versatility of ball mounts ever since. Douglas Arion (one of the prime forces behind the Galileoscope project, galileoscope.org) feels the same way. He says, “I hate axes. If you build a mount with them they’re hard to set up without play, and you always end up with dead spots — the pole for equatorials, the zenith for alt-az. Equatorially mounted Newtonians really need tube rotation, too, so that has to be added to the design. Spherical mounts have none of those problems. No dead spots, no inconvenient eyepiece locations, and they are intrinsically stable.” Doug has found a convenient source of spheres for his mounts:…

In this new regular section of the magazine, we’ll profile leading amateur astronomers and astrophotographers from across Australasia. We start off with Queenslander, Dylan O’Donnell, who has rapidly made a name for himself in astro circles for his imaging prowess and for organising the Star Stuff festival at Byron Bay. What got you into astronomy? I’d always had an interest in space generally, but when I became a new parent and couldn’t play my guitar at night anymore (lest I wake the baby) I bought a $1,000 telescope on an impulse. I joined the Southern Astronomical Society and I’ve been broke ever since! What was your first telescope set-up? That first telescope was a Celestron 4SE which I used for lunar, solar astrophotography, visual and even a bit of wildlife…

IT’S SMALL AND GREY and covered with craters — and, no, it’s not the Moon. At first glance, Mercury looks a lot like Earth’s natural satellite. Both have lava plains and rugged cratered terrain, with bright streaks radiating out from powerful impact scars on their drab, airless surfaces. But the Sun-scorched innermost planet is a very different place, from its inside out. In contrast to the Moon’s puny core, Mercury’s iron heart takes up some 80% of the planet’s radius. It’s still at least partially molten and generates a weak, global magnetic field. Moreover, the planet’s ongoing, slow solidification affects its surface: As the core freezes, it shrinks, and the crust wrinkles like a drying plum, creating ridges that cut right across big craters. Look closely at those craters, and…

ASTRONOMY 2019 YEARBOOK Every astronomer needs the Astronomy 2019 yearbook. Australian-produced, it is packed full of essential information to plan your observing sessions. Included is a complete guide to what’s visible in the night sky, including Moon phases, planets, comets, eclipses and meteor showers, plus star maps and a month-by-month viewing guide. $29.95 plus postage & handling 2019 AUSTRALASIAN SKY GUIDE An ideal yearbook for beginners, the easy-to-read 2019 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. $16.95 plus postage & handling ASTRONOMY 2019 CALENDAR Featuring amazing celestial photography from the annual David Malin Awards, the Astronomy 2019 Calendar provides a guide to…

The three ground-based telescopes that are the topic of this double feature — the Giant Magellan Telescope, the Extremely Large Telescope and the Thirty Meter Telescope — are expected to achieve first light in 2024, 2024 and 2028, respectively. They will no doubt revolutionise astronomy. So what about the James Webb Space Telescope (JWST), due to be launched in 2021? How does Webb compare to the monster scopes of the future? Ironically, working against the largest space telescope ever built is its small size. With its 6.5-metre segmented mirror, Webb will collect only 3% as much starlight as that which will hit the 39.3-metre primary of the ELT. Also, its science instruments are designed to fit into a limited space. However, JWST doesn’t suffer from the background glow of the…

January 21–25 Venus and Jupiter, both very bright, are close together in the morning sky. February 8 The Alpha Centaurid meteor shower peaks this morning. 12–13 Mars and Uranus appear close together. Use binoculars to see them in the one field of view. 18–19 Venus and Jupiter shine together in the east as morning twilight brightens. Venus is the brighter of the two planets. March 15 The Gamma Normid meteor shower will peak this morning. 21 Equinox. Today the hours of daylight and darkness will be almost equal. April 12 Mercury is well placed for morning observing all month, with greatest elongation from the Sun today. 25 Saturn will be occulted by the Moon as seen from most of New Zealand and Australia. 26 The waning gibbous Moon will be…

Guy Ottewell has quoted Manilius: Nunquam futilibus excanduit ignibus aether — “The ether never blazed with futile fires” — and Guy quite rightly added, “That is to say: all meteors mean something.” I agree. Every meteor means beauty, surprise, wonder, and a stirring of thought for its fortunate observer. Fred Schaaf, The Starry Room If you had been reading these words in October, you might have been getting ready for the Orionid meteor shower — flaming debris from past returns of Halley’s Comet. Of, if it had been in early November you might have been on the lookout for a few fireball-bright Taurids as the Bull ascended in the east and northeast through the evenings, reaching its highest in the middle of the night. Or around November 17 you might…

The parade of bright, short-period comets that graced our skies during the closing months of 2018 has now all but ended, with the comets having grown faint or, in the case of 46P/Wirtanen, travelled too far north to be of interest to Southern Hemisphere observers. For January, the only one of the short-period comets of last year to hold any real prospects for observers with small telescopes is the Halley (orbital)- class 38P/Stephan-Oterma. Even this object will be well north of the celestial equator and, as such, reserved for observers with good skies and a clear northern horizon. Having passed perihelion at 1.59 a.u. from the Sun on November 10 last year and 0.76 a.u. from Earth on December 17, the comet is unlikely to be any brighter than magnitude…

Worshipped as Juventas in ancient Rome, the goddess Hebe makes only fleeting appearances in ancient Greek myths. From Hesiod, we learn she’s the offspring of Hera and Zeus. Ovid portrays her as the personification of youth and rejuvenation, capable of making even an old man young again. In Homer’s Iliad, she appears at a war council, filling golden cups with nectar for the gods while they debate the Trojan War. Fortunately for us, Hebe’s appearance in the night sky in the form of a main-belt asteroid lasts longer than a few sentences. The stony asteroid 6 Hebe, discovered in 1847, spends most of December looping across Monoceros before crossing into Orion on the 29. Observing conditions improve the deeper into the calendar we go. For those observing from around latitude…

As an astrophotographer, I long to image faint targets in the night sky. The problem, though, is that I live under skies awash with skyglow, as many of us do. And while I enjoy taking road trips to dark skies in an effort to image under better conditions, nothing quite beats the convenience and comfort of imaging from my own backyard. Despite being barely able to discern the Milky Way on most clear nights, I’ve still been able to take many colourful, detailed images of galaxies, nebulae and star clusters from my suburban home. Here are some of the ways I’ve found to mitigate the effects of light pollution — common-sense steps that might help you get the most out of your own location. Shoot high My backyard is only…

SKY-SWEEPING ASTROGRAPHS Celestron ♦ celestron.com Building on the success of its 27.5-cm (11-inch) Rowe-Ackermann Schmidt Astrograph (RASA for short), Celestron has introduced 20-cm f/2 and 35.5-cm f/2.2 RASAs for 2019. These specialised instruments are strictly for imaging with cameras that mount on the astrographs’ front corrector plates. Their incredibly fast optical speeds enable deep sky imaging with short exposures, opening up a new world of scientific and recreational astrophotography possibilities. U.S. price: $1,699 and $13,999 (20- and 35.5-cm, respectively) ZERO BACK FOCUS BINOVIEWER Orion Telescopes & Binoculars ♦ oriontelescopes.com You don’t have to hunt far on the internet to find observers waxing poetic about using binoviewers for two-eyed gazing through telescopes. What makes the new Premium Linear BinoViewer for Telescopes special is that it’s the first we’ve seen that requires…