Innholdsfortegnelse for February - March 2020 i Australian Sky & Telescope

A GROUP OF VOLUNTEERS known as ‘The Barrys’ has been working alongside Museums Victoria experts since 2008 on restoration of the Great Melbourne Telescope (GMT), which was once the largest telescope in the Southern Hemisphere and the second-largest in the world. The team has spent 30,000 hours getting the instrument into shape for a major milestone achieved in November — reassembly of the main structure for the first time in 74 years. The 10-metre-high, steel truss telescope was first installed at Melbourne Observatory in 1869. There it stayed until the Observatory closed in 1944, at which time the GMT was sold and relocated to Mount Stromlo Observatory. In the early 1990s it was transformed into Australia’s first robotic and computerised digital imaging telescope for the international MACHO Project, which found…

A TRAIL OF BLOOD on the ground tells you someone is wounded. Likewise, the discovery of an unusual stream of gas onto a white dwarf star betrays the presence of a ‘bleeding’ planet. Astronomers have reported the first-ever, albeit indirect, evidence for a planet orbiting a white dwarf — the dense remnant of a Sun-like star that has used up its nuclear fuel. In the December 5 issue of the scientific journal Nature, a team of astronomers led by Brian Gänsicke (University of Warwick, UK) describes their study of a 19th-magnitude hot white dwarf known as WD J091405.30+191412.25, located some 1,500 light-years away in the direction of the eastern part of Cancer. Observations with the X-Shooter spectrograph on the European Southern Observatory’s (ESO) Very Large Telescope reveal the existence of…

OF THE MANY CHEMICAL ELEMENTS that stars create, none is more vital to terrestrial life than carbon. About half the carbon in your body arose from red giant stars, which minted the element in their interiors and then dredged it up to their surfaces, transforming themselves into carbon stars. They cast the element away when they ejected their carbon-coated atmospheres and became white dwarfs. As if beckoning their progeny on Earth, carbon stars boast beautiful ruby hues that have long attracted observers: “the most intense crimson, resembling a blood-drop,” wrote 19th-century astronomer John Russell Hind of the carbon star R Leporis. Although this stellar gem is known as Hind’s Crimson Star, William Herschel spotted it first, calling it “A bright garnet star …a most beautiful colour” four years after discovering…

The Gamma Normids meteor shower is active from February 25 to March 28. This year there are two peak periods predicted, the first being March 14 and the second, and the more favourable, on the 25th. Unfortunately the 14th will be affected by the gibbous Moon, but the 25th will be under Moon-free skies, so it will definitely be worth a look. This shower is known for its bright and swift meteors, which regularly leave trains and are often green in colour. The zenithal hourly rate prediction for this year is between 3 and 5 meteors per hour on both dates. The radiant is located near the star Gamma 2 Normae. Unfortunately the other active shower during this period, the Alpha Centaurids, will be washed out by the near-full Moon.…

In our last issue we looked at how to make a variable star brightness estimate, using the Mira-type variable TT Monocerotis as our example. If you’ve got that issue handy, give it another look. As shown on our finder chart above, you can use that field to star hop just under 2 degrees south to today’s target, V694 Mon. I latched on to this star in 2005 because, like a baited hook, the chart I had at the time labelled the variable as ‘type unknown’. V694 Mon is in fact a symbiotic star, an interacting binary system comprising a red giant and white dwarf. In V694 Mon’s case the system has an accretion disc expelling a jet of gas that just happens to be pointed at us along our line…

Asteroid loyalty Asteroid 37 Fides, named for the Roman goddess of loyalty, will be plying the star-poor byways of eastern Cancer over the next couple of months. Fides is a large S-type, or stony, asteroid 108 kilometres across that spins once every 7.33 hours. Based on its unusual light curve, which displays three minima and three maxima, some astronomers think it might be a binary object. At opposition on February 2 and brightest at magnitude 10.1, Fides will slowly fade thereafter as it moves west in retrograde, almost reaching the Beehive Star Cluster (M44) by the end of March. Jupiter in the morning Jupiter reemerged from behind the Sun in January, and it’s readily observable at or before dawn in February. Although it rises while the sky is still fully…

Eddie Trimarchi has been an amateur astronomer for many years. His superb astrophotography has garnered praise and awards, including a Highly Commended from the Royal Observatory, Greenwich in the 2011 Astronomy Photographer of the Year. What got you into astronomy? In 1971 at the age of nine, I was already consumed by the Mercury, Gemini and Apollo space missions. That year, North Griffith Primary School arranged my first school excursion with my class all the way to Canberra. Unbeknownst to me, the consent form I had to fill out — on which I put astronomy and tennis as my only interests — would result in me meeting Edwin ‘Buzz’ Aldrin, who was a friend of the family with whom I had been billeted. Buzz was visiting Canberra at the time…

THE NIGHT SKY IS NOW CLEAR and dark. With a limiting magnitude of 3.5, it’s a good night. So I set up the telescope for some deep sky imaging. My site is not ideal. I’m imaging from my 9th-floor balcony in heavy light pollution amidst a city with population of five million. Having no convenient access to a dark sky, I work with what I have. Other amateurs who live in cities might not even try urban astronomy, figuring ‘What’s the point?’. I used to observe in the usual way, eyeball to eyepiece, using my 20-cm Schmidt-Cass Go To telescope. Finding targets in a washed-out sky proved difficult, but I didn’t give up. I wanted more. So I set the eyepieces aside and invested in an astronomical camera and a…

FOUR DECADES AFTER its launch into the outer Solar System, Voyager 2 exited the heliosphere, the cavity around the Sun blown out by the solar wind. It crossed over on November 5, 2018, six years after that of the speedier Voyager 1. Voyager 1 returned a surprisingly messy view of the outer boundary, known as the heliopause, that separates the Sun’s domain from the interstellar medium. Voyager 2 promises a point of comparison. In the November issue of the scientific journal, Nature Astronomy, five teams of astronomers analyse the spacecraft’s report from the frontier of the Solar System. Particles at the edge of the heliosphere are hot and sparse — a mere 0.002 electron per cubic centimetre, Donald Gurnett and William Kurth (both at University of Iowa) report in their…

The Milky Way’s centRe is relatively quiet, but it wasn’t always that way. Two new studies shed light on our galactic center’s tempestuous past. In the first study, Ian Heywood (University of Oxford, UK) and colleagues find a pair of outflows emanating from our galaxy’s centre using the MeerKAT radio telescope array in South Africa. These radio lobes are reminiscent of the gigantic Fermi bubbles, but while those each span some 25,000 light-years above and below the disk, the MeerKAT dumbbell is only 1,400 light-years long end to end. The researchers estimate that whatever blew up the MeerKAT bubbles, it happened a few million years ago. Perhaps, the authors speculate in the September 12 issue of Nature, the MeerKAT event was a miniature version of whatever made the Fermi bubbles.…

The Auckland Astronomical Society’s annual Harry Williams Astrophotography Competition has once again attracted a wide range of exceptional entries from some very accomplished astrophotographers. With subjects spanning from near the (the aurora) to the far (NGC 5128), they ably capture the essence of our marvellous southern skies. Australian Sky & Telescope is proud to be a sponsor of the competition, and we congratulate all of the winners and runners-up. You can see more competition photos at astronomy.org.nz…

EVERY JANUARY MY ASTRONOMY CLUB hosts a workshop in which we help people learn how to use the telescopes they got for the holidays or tune up scopes that have been gathering dust in closets. And every year we face the same problem: how to gently tell some of them that what they’ve got is better suited for a boat anchor than for astronomy. It may be hard to believe, but some telescopes are worse than having no scope at all. When you want to enjoy a night out under the stars, you’re better off with a pair of binoculars or just with your naked eyes than with a telescope that can’t be aimed easily and doesn’t show a pleasing view of whatever you do manage to point it at.…

There are tens of thousands of them in the Milky Way Galaxy. Given a good, dark night sky you can see some of them — with your telescope, your binoculars, even your unaided eyes — in any season. Yet we shouldn’t take these objects for granted. And there’s a season, even a particular month, that’s arguably the best for viewing them. The month I’m talking about is February. The objects I’m talking about are open star clusters. Open season on open clusters. The entire February evening Milky Way — from the last peek of Auriga in the north to Centaurus low in the south — is splashed with open star clusters. Many of these clusters are marked on our all-sky map. This includes two pairs of clusters that are a…

The most challenging observing targets in the Solar System are located right in our cosmic backyard, yet they can’t be seen through a telescope. The path that led to their discovery six decades ago can be traced back almost two and a half centuries to attempts to solve the vexing ‘three-body problem’ in celestial mechanics. In 1772 the mathematician Joseph-Louis Lagrange determined that a relatively small body that shares the orbit of a planet and lies 60° ahead or behind it will maintain its position for an indefinitely long period of time. These Lagrangian points are designated L4 (leading) and L5 (trailing). Forming a pair of equilateral triangles with the planet and the Sun, they are exceptionally stable because the gravitational attraction of the planet and the Sun on the…

GEAR CONTROLLER Software Bisque announces TheSky Fusion (US$1,695), a compact, mountable control computer for your imaging system. TheSky Fusion simplifies setups by powering and controlling a broad range of astro-cameras, filter wheels, focusers and other devices using a Linux operating system that eliminates the need for Microsoft Windows and its disruptive updates. It includes a pre-installed 64-bit professional edition of TheSkyX software configured for imaging. As a complete embedded system, TheSky Fusion draws much less power than a normal computer, and its fast performance shouldn’t degrade over time. The unit includes a 64-bit Hex-Core 1.8 GHz CPU with 256 GB of mass storage space and 4 GB of RAM. A status display panel reports current operations and includes built-in GPS, eight Anderson Powerpole ports, four USB 3.0 ports and an…

There are some major events coming up on both sides of the Tasman in the coming months. It’s not long now until Astrofest 2020 in Perth, which will be held on February 29 (5:30pm to 9:30pm at the Curtin Stadium, Kent Street, Perth). One of the biggest public astronomy events in Australia – if not the biggest — Astrofest attracts thousands of people who get together to celebrate and enjoy the night sky, while partaking of fun activities and educational opportunities. There’ll be lots of displays, telescopes to look through, a model of the Square Kilometre Array, a portable planetarium, announcement of the winners of the Astrofest Astrophotography competition and lots more. Check out astronomywa.net.au for full details. The Royal Astronomical Society of New Zealand’s (RASNZ) annual conference is another…

Observations from the Stratospheric Observatory for Infrared Astronomy (SOFIA) confirm suspicions that dust surrounding BD+20 307, a binary star system 390 light-years from Earth, came from a recent collision between planet-size bodies. The two stars of the BD+20 307 system are at least a billion years old, so any debris left over from their formation should have cooled down a long time ago. But when astronomers first imaged the system 15 years ago using ground-based telescopes and the Spitzer Space Telescope, they found an abundance of warm dust. The presence of this dust suggested a collision occurred tens of thousands of years ago between two large worlds in the system. One decade later, astronomers used SOFIA, an infrared telescope that flies aboard a modified Boeing 747, to follow up on…

Most ‘normal’ mass is contained not in stars but in gas that extends far beyond any galaxy. This gas is thought to fall onto galaxies over time, providing fuel for star formation. In turn, stars — or rather, the winds they produce as they’re born and as they die — are thought to replenish that reservoir. For the first time, David Rupke (Rhodes College) and colleagues directly observed evidence of that replenishment using the Keck Observatory’s Cosmic Web Imager,. The KCWI, an integral field spectrograph, took simultaneous images and spectra of a giant wind flowing out of a galaxy into the sparser medium that surrounds it. The galaxy, named Makani (‘wind’ in Hawaiian), has probably driven this tempest via bursts of star formation ignited during a merger with another galaxy.…

IN FEBRUARY OF 1977, an oceanographic expedition studying hydrothermal vents at the bottom of the Pacific Ocean made a discovery that changed biology forever. Two kilometres deep, near a volcanic zone northeast of the Galápagos Islands, explorers aboard the deep-ocean submersible Alvin found four dense agglomerations of clams, mussels, crabs, anemones and other creatures. Some of them were living among an alien-looking variety of tubular worms that vaguely resembled giant albino tulips. In awe, the researchers — probably inspired by the stark contrast with the barren seafloor beyond the vents — named the fourth, tubeworm-bedecked spot the ‘Garden of Eden’. At the time it was a mystery how this lush ecosystem could survive at such depth. Biologists had assumed that sunlight was the energy source that powered all life on…

I’m sure I’m not the only stargazer who is frequently arrested by the sight of the constellation Orion striding across the night sky. In fact, the celestial Hunter ensnared my attention so successfully that it took me years to discover the riches of the nearby constellation Monoceros, the Unicorn. Monoceros has few bright stars, but since it lies squarely in the summer Milky Way it contains an almost unbelievable density of star clusters and nebulae. On one of my first ‘unicorn hunts,’ I stumbled across something remarkable. Right on the celestial equator and about halfway between Beta (β) and Epsilon (ε) Monocerotis (the latter is also known as 8 Mon), I found a field so rich that I assumed it must have a name. The group is anchored by a…

Have you ever stood on a bit of land where you could climb no higher, or go no farther in the direction you were travelling? I often wonder when I view the sky how far I can see in a given direction. Using only our eyes, looking toward Sagittarius we run into the dense gas and dust of our galaxy’s plane before we reach its centre, around 26,000 light-years away. Turning to Andromeda and its iconic galaxy, we have 2.5 million light-years to M31, and in Centaurus it’s about five times farther to the brightest radio galaxy, Centaurus A (NGC 5128), possibly the most distant object visible to the naked eye. With binoculars or a telescope the exercise becomes more complex. Choosing our targets I recently wondered which is the…

FOCUSING A TELESCOPE can take a great deal of fine-tuning and finesse. It’s hard enough to focus a telescope or lens by eye, even though most eyes are somewhat forgiving. Once you’re within the range of a half-diopter or so, the eye’s internal process of focus accommodation automatically takes over, at least for young eyes. Of course, there are mechanical constraints that have nothing to do with the quality of the image viewed. For example, manually adjusting the focus knob makes the view jiggle around the field. An image that jumps and shakes instead of standing still is impossible to focus, no matter how you measure success. Motorised focusers mostly solve these mechanical constraints — judgment of focus becomes nearly real-time, if the focusing action is slow enough. Most solutions…