Innholdsfortegnelse for Jul 2016 i Australian Sky & Telescope

have a few welcomes and one farewell to make. First the farewell. Gary Seronik, who has been writing about observing and telescope making for 20 years, is moving on to become editor of the Canadian magazine, SkyNews. I know that you, the reader, and all of us here at Australian Sky & Telescope have benefited greatly from Gary’s many years of contributions, and we wish him all the best in his new gig. Taking over from Gary are two new authors, the first of whom, Mathew Wedel, will be writing most of our Binocular Highlights columns. A paleontologist and professor of anatomy by day, by night he is what he calls an “adventurous stargazer”. And we also welcome Jerry Oltion, who is taking over Gary’s Telescope Workshop column under the…

A massive cloud falling toward our galaxy’s disk is likely from the Milky Way itself, not a visitor, a new study shows. This object, called the Smith Cloud, lies 40,000 light-years away and contains 2 million Suns’ worth of gas, primarily hydrogen. It’s falling toward the galactic disk at nearly 102,000 km/h. The Smith Cloud is one of the best characterised high-velocity clouds, speedy wisps that rain down as a light drizzle onto our galaxy. This shower helps fuel star formation. But despite these clouds’ importance, astronomers know a paltry amount about what they’re made of and where they come from. Andrew Fox (Space Telescope Science Institute) and colleagues used the Hubble Space Telescope and the 91-metre Green Bank Telescope to better understand the Smith Cloud’s makeup. The astronomers took…

This month’s focus reminds us how much the modern discipline of astronomy (‘the measurement of the stars’) is rooted in the older practice of astrology (‘the knowledge of the stars’). It seems that as long as we have been aware of the movements of the night sky, most notably the changing positions of the Sun, Moon and planets against the background of the ‘fixed stars,’ we have looked to them to give guidance as to our daily lives and our fates. For a great many ancient scholars, casting ‘horoscopes’ to forecast the future for their patrons or other significant people was a prominent item on their duty statements. It was therefore important to be able to predict where the seven classical celestial objects would lie among the stars in years…

Many stargazers don’t observe exclusively with either binoculars or a telescope, but switch back and forth as needed. There’s a lot to be said for examining the same astronomical target with different instruments. I was reminded of this when I revisited NGC 6633, an open cluster in the eastern reaches of Ophiuchus. When I was a newcomer to astronomical sketching, this cluster was one of my first targets. Only later did I learn its nickname: the Italy Cluster. Michele Bortolotti and Guido Rocca of Verona, Italy, had pointed out that NGC 6633 was reminiscent of their home country’s famous ‘boot’ shape. Because I’d used a reflector, my sketch was inverted. When I turned the drawing around, Italy’s shape was not just obvious, it was unavoidable. There’s even a stellar Sicily…

The long, dark nights of winter are here, bringing colder conditions but hopefully clear, crisp skies (depending on where you live, of course). The Milky Way is stretching from northeast to southwest, with the Southern Cross high in the southwest and Scorpius overhead from mid-southern latitudes. Mercury is lost in the Sun’s dawn glare for the first week of July, reaching superior conjunction (ie. on the opposite side of the Sun from us) on the 7th. By mid-month it will have begun to make a reappearance in the evening sky to the west. On the 17th, the tiny planet will appear very close to Venus — they’ll be only half a degree apart, but low in the twilight less than 3° above the horizon. You’ll need a clear western horizon…

“This comet was considered ‘lost’ for many years.” It looks like C/2013 X1 (PANSTARRS) will still be the comet of chief interest for Southern Hemisphere visual observers during the month of July. As we noted in the previous issue, this comet passed perihelion (closest point to the Sun) on April 20 at 1.31 astronomical units, and passed Earth on June 21 at a distance of just 0.64 a.u. July, therefore, will see 2013 X1 pulling away from both Earth and Sun and fading relatively quickly — although if it lives up to its early promise, it should remain a good object for binoculars and small telescopes throughout the month. July begins with the comet in the southern constellation Ara and (from brightness parameters derived early this year) possibly around magnitude…

All lunar observers know Copernicus, Plato, Tycho and probably a handful more of the 895 named craters on the nearside. But did you know that an additional 5,433 nearside craters have designations? These craters bear letters, not names. For example, a small dark halo crater southeast of Copernicus is called Copernicus H. And Petavius B, just north of its namesake, is a wonderful oblique impact crater with asymmetric rays. Imagine the nightmare it would be for observers who wanted to learn their way around the Moon’s surface if each of those 6,328 nearside craters had a distinct name honoring some historical figure. That’s why letter designations exist for smaller or less prominent craters. When I wrote ‘Copernicus H’ above, you probably knew immediately in what part of the Moon this…

Which are the ‘best’ open and globular star clusters in the southern sky? While astronomers in the Northern Hemisphere have the Messier catalogue to guide them, here in the south we lack a similar list. However we can be guided by two outstanding astronomers of the 18th and 19th centuries whose observations point us in the right direction. Between them, these two men found most of the open and globular clusters the southern sky has to offer. First up is Frenchman, Nicolas-Louis de Lacaille (1713–62). In 1751 and 1752, observing from Cape Town with just a crazily small Ѕ-inch refractor, he found most of the bright open clusters of the southern sky. Well-educated and well-financed, he produced a catalogue of 42 clusters and nebulae as well as a catalogue of…

I love to build things. I also love to share what I’ve learned in the process. If you’ve followed Gary Seronik’s Telescope Workshop column over the years, you’ve seen some of my projects, including my flex equatorial platform highlighted in the April issue. So when Gary told me he was becoming editor of SkyNews, and Australian Sky & Telescope asked if I’d be interested in continuing his column, I jumped at the chance. Gary left a mighty big pair of shoes to fill. I will never replace him; all I can do is continue the column in my own way and do my very best to keep it as interesting and informative and inspiring as he did. You’ll notice one change, however: the title at the top of the page.…

ETA CARINAE Mervyn Millward Clouds and bushfire smoke tried their best to ruin this shot, but Mervyn persisted to complete the 3x3 mosaic of Eta Carinae and the surrounding region. He used a Takahashi Mewlon 250mm CDK Cassegrain reflector and QSI 683 camera. Each of the nine images comprised 10 x 300 seconds of luminance and RGB. GALAXY RISING Nicholas Thompson Seventeen-year-old Nick snapped this 30-second shot of the Milky Way just after midnight on April 3, from Wyaralong Dam (near Brisbane). He used a Nikon D7100 with a Tokina 11–16 f/2.8 lens at 11mm. SELENE SCENE Rene Martens Our unchanging Moon was the target for Rene, a professional photographer. He used a Canon 6D camera and Sigma 50–500mm lens. FOWL PLAY Greg Burrows Known variously as the Running Chicken…

Shedding light on the ‘diamond planet’ New observations are helping characterise the atmosphere of an exotic exoplanet. Angelos Tsiaras (University College London) and his team took an infrared spectrum of the super-Earth 55 Cancri e (now called Janssen). It’s the first successful measurement of a super-Earth’s atmospheric composition. The team found tantalising hints of hydrogen cyanide (HCN). This molecule would only dominate in a carbon-rich environment, instead of one based on oxygen-rich silicates as on Earth. That supports researchers’ suspicion that this dense world, nicknamed the ‘diamond planet,’ contains crystallised carbon in its interior. The team also found no trace of water vapour, which would form easily if oxygen were widespread on the planet, the astronomers report in an upcoming issue of the Astrophysical Journal .…

WHEN Early June 10 p.m. Late June 9 p.m. Early July 8 p.m. Late July 7 p.m. These are standard times. HOW Go outside within an hour or so of a time listed above. Hold the map out in front of you and turn it around so the label for the direction you’re facing (such as west or northeast) is right-side up. The curved edge represents the horizon, and the stars above it on the map now match the stars in front of you in the sky. The centre of the map is the zenith, the point in the sky directly overhead. FOR EXAMPLE: Turn the map so the label ‘Facing North’ is right-side up. About halfway from there to the map’s centre is the bright star Arcturus. Go out…

Late July will bring one of the better meteor showers for Southern Hemisphere observers, the Southern Delta Aquariids, so called because the radiant — the point from which the meteors appear to fan out across the sky — is located near the star delta Aquarii, in the constellation Aquarius. The meteoroids that produce the shower probably had their origins in the aftermath of the breakup of a comet that produced the Marsden and Kracht families of ‘sunskirting’ comets. The shower is rich in faint meteors, but occasionally bright members have been spotted. Southern Delta Aquariids are usually blue or white in colour, with the average magnitude being +4.0. The zenithal hourly rate (ZHR) can vary from 15 to 30 meteors per hour from a dark rural sky; from town, rates…

Just as it is for all astronomers, variable star observers need to locate the right field before looking for a target. In fact, we have one very special reason — if the star is at its minimum light, it might not be visible at all. This month we’ve got a field that’s hard to top; perfect for binoculars or small telescopes, straddling the Galactic equator and looking inwards toward the Galactic hub. In fact, we’re looking out from our Local Arm of the Milky Way, across the void, and then some way into the Sagittarius-Carina Arm. The chart shows our main target, V905 Scorpii. It also shows one globular and six open star clusters, a dark nebula, and variable stars BM Scorpii and RY Scorpii, which are themselves worthwhile targets.…

The closest planetary moons to Earth, after our own familiar Luna, are Phobos and Deimos orbiting Mars. Most amateurs have never seen them. With Mars having just reached its close approach to Earth, now’s a good time to seek them out before the planet and its moons get too far away. The problem with seeing Phobos and Deimos through a telescope isn’t that they’re too dim. You might think they’d be fairly easy, since they shone at magnitudes 11.4 and 12.5, respectively, in the week or two around Mars’ May 30 closest approach. (The planet and its moons are a half magnitude fainter by the beginning of July.) The problem is that they orbit so close to Mars amid its dazzling glare. Mars blazes 230,000 and 600,000 times brighter than…

The most luminous supernova ever discovered, ASASSN-15lh, challenges popular theories for blazingly bright exploding stars. The supernova appeared in June 2015 in the southern sky in images taken by the All-Sky Automated Survey for Supernovae (ASAS-SN). Its light travelled for 2.8 billion years to reach Earth, giving it a redshift of 0.2326. Due to its distance, its glow peaked at only 17th magnitude. But its intrinsic luminosity was twice as bright as any supernova yet discovered. Six months later, this single object continued to emit a level of energy that rivalled that of all the stars in the Milky Way combined. Subo Dong (Peking University, China) and colleagues released an update in the January 15 issue of the journal, Science. ASASSN-15lh was more than 10 times brighter than Type Ia…

In 1890, astronomy was the enterprise of a scattered coalition of amateur and professional scientists working on a roughly equal basis. Both camps conducted essential observations, innovated with new technology, published important papers, attended conferences, joined scientific organisations and received awards of merit. But as that crucial decade progressed, distinctions between the two groups rapidly began to widen — in terms of academic credentials, mathematical acumen, and, most devastating to the amateurs, the scientific value of their work. Disruptive new technologies — photography and spectroscopy — were fast overtaking traditional visual observation. Productivity imperatives, and the escalating cost of leading-edge equipment, increasingly displaced gentlemens’ private observatories in favour of externally funded institutions with professional staffs. By the decade’s end, amateur researchers found themselves effectively sidelined by their institutional brethren. Then…

Afar-future geologist studying Earth history would note that our time was one of sudden and unprecedented changes. Could this be a type of transition that other planets also go through, when cognitive systems begin to influence global systems? I’ve written before about the proposal to formally rename our current geological epoch the ‘Anthropocene’ to acknowledge the fact that humans have become a major force of global modification. Within geological and other academic circles it’s been contentious but fruitful — sparking interesting debates about how we humans should regard, and attempt to guide, our own planet-altering presence. But there’s no consensus over when exactly this humanised age began. Did it arise with the first atomic bomb explosions in the 1940s? If there was ever a time when we started to realise…

For those keen on observing double stars, the second edition of the Cambridge Double Star Atlas (CDSA) is now out. In this new edition the 30, double-page star charts, produced by famed uranographer Wil Tirion, have been partly revised because of changes in the selection of the doubles. As before, the CDSA marks more stars on the charts as double than are described in the data listings. The pages are a generous 23 x 30 cm in size and stars to a combined magnitude of 7.75 are shown, along with many of the brighter deep sky objects, so it can also be used as a general purpose atlas. All up, 2,500 doubles have more detailed data listed than in the first edition, and with HD and SAO catalogue numbers added…

High overhead in the mid-to late-evening at this time of the year, rides the magnificent spectacle that is the constellation Scorpius. One of the few star groupings to actually resemble the creature, god or item it is meant to represent, Scorpius is certainly one of the most recognisable of the 88 modern constellations. And we’re fortunate indeed, here in the south, to have it perfectly placed for our viewing pleasure. Wedged between Sagittarius to the east and Libra to the west, Scorpius encompasses a rich region of the Milky Way, full of star fields, star clusters and nebulae, making it a fabulous target for either binocular or telescopic observation. You’ll find the open clusters Messier 6 and Messier 7 — both of which can been glimpsed by the naked eye…

“A William Herschel discovery, it’s a wide pair and easy for small telescopes.” Libra, the Scales, a Zodiacal constellation that precedes the claws of Scorpius across the sky, is our area of focus this month. We begin with 33 Librae (H N 28), which is found nearly 6 degrees south-southeast of Alpha Librae. A William Herschel discovery, it’s a wide pair and easy for small telescopes, the stars being 6th and 8th magnitudes. Hartung in his classic observer’s guide noted an unusual colour combination of “orange and red” as seen with his 31-cm reflector. Six degrees southeast from 33 Librae are two doubles in the same field of view. BU 227 is the easier, accessible to an 80-mm telescope. The middle star in a line of three, I saw it…

Serpens, the Serpent, is the only one of the 88 modern constellations that’s divided into separate pieces on the sky. Serpens Caput, containing this immense snake’s head, is to the west of the ‘serpent bearer’ (Ophiuchus), while Serpens Cauda, the beast’s tail end, coils to his east. In the June 2015 issue we scanned some of the wonders of the snake’s head. Now let’s see what tales the tail can tell about our deep sky. The starting point for our sky tour is the tip of the serpent’s tail, Theta (Ø) Serpentis, a double star also known as Alya. Alya marks the top of a U-shaped asterism. The four stars that compose the U’s sides are dressed in shades of yellow and gold, but Alya is arrayed in white. Through…

Australasia is facing a dearth of total solar eclipses in the coming years. There’ll be a hybrid eclipse in 2023, when the central path will just clip the edge of the Australian mainland in northwestern Western Australia. The next total eclipse will be a beauty, stretching right across Australia and passing right overhead Sydney and then on to the southern tip of New Zealand — but it won’t be until 2028. If you can’t wait that long, you might want to consider travelling to see the 2017 total solar eclipse, which will be seen in its entirety from the USA. There are plenty of companies out there providing tours and packages, but before you decide on where to go, you might like to brush up on all the details of…