Innholdsfortegnelse for February/March 2017 i Australian Sky & Telescope

WHERE WERE YOU ON THE NIGHT OF FEBRUARY 24, 1987? I was at home, minding my own business, when the phone rang. It was an amateur astronomer friend, who told me to go outside and take a look at the Large Magellanic Cloud. “Why?” I asked. “Because there’s a supernova!” he said. And sure enough, there was. It was the first supernova discovered that year, so it was given the name SN1987A. But what was special about it was that it was bright enough to be visible to the naked eye — the first such supernova in almost 400 years! Astronomers, both professional and amateur, dropped everything and turned every available instrument onto it…. knowing full well that it might be another four centuries before such an opportunity presented itself…

CASSINI DATA suggest that a subsurface ocean might lie deep beneath the crust of Saturn’s moon Dione. Planetary scientists have found evidence of subsurface oceans lurking beneath the crusts of several Solar System bodies. The most convincing case is Enceladus, a little icy moon of Saturn known for its salty geysers. Other contenders are Saturn’s largest moon, Titan, and Jupiter’s big moons Europa (see below), Ganymede, and Callisto. At the March 2016 Lunar and Planetary Science Conference, Doug Hemingway (University of California, Berkeley) and others on the Cassini radio science team presented a preliminary analysis suggesting that Dione might have a subsurface ocean, too. They based this conclusion on the moon’s overall topography and how strongly it pulls on the Cassini spacecraft, which has been touring the Saturnian system since…

THE RECENTLY DISCOVERED object 471325 (formerly 2011 KT19 ) hints that a distinct new class of high-inclination Centaurs lurks in the distant Solar System. Centaurs are objects whose orbits cross those of one or more outer planets. They generally lie between Jupiter and the Kuiper Belt. Observers with the Catalina Sky Survey first spotted 471325 in 2011. It turned up again last year in images taken in the constellation Serpens Caput with the Pan-STARRS 1 telescope in Hawai‘i. Based on its 22nd-magnitude brightness, this object should be 70 to 200 km in diameter — at most one-sixth the diameter of Pluto’s large moon, Charon. But it’s the orbit derived by Ying-Tung Chen (Academia Sinica, Taiwan) and others that shows what a strange little world this is. Reported in the August…

METEOR SHOWER OBSERVING in summer is great fun, and a great way to start 2017 is with the Alpha Centaurids. This shower is active from January 28 to February 21, with the maximum falling on February 8. The radiant — just near Beta Centauri — is almost circumpolar at this time of year, and so is very well placed from late evening onwards. And this year the waxing gibbous moon will set some hours before dawn, leaving you plenty of time to observe in dark skies. The Alpha Centaurid shower is known for producing very bright meteors, but numbers are usually low. In 2015, many observers reported some very bright meteors, and half a dozen fireballs were reported days before, and after, the February 8 peak. That year also saw…

FOR DECADES astrobiologists have pondered whether primitive life might exist in a global ocean presumed to lie beneath the smooth, icy crust of Jupiter’s moon Europa. But this putative ocean must be at least several kilometres down — a formidable barrier to exploring it firsthand. Now it appears that sampling this briny deep might be easier than once thought. Hints that Europa sports water-powered geysers first came to light in 2012, when a team led by Lorenz Roth (Southwest Research Institute) used the Hubble Space Telescope (HST) to spectroscopically detect localised clouds of hydrogen and oxygen atoms — presumably derived from water — in Europa’s vicinity. More recently, William Sparks (Space Telescope Science Institute) and others used HST to record images of Europa as it crossed in front of Jupiter.…

ONCE THE ADVENT of the ‘space age’ late in 1957 gave us the capacity to send machines into Earth orbit and beyond, the Moon, as the closest extraterrestrial object, was the obvious first target for exploration. Within a few months of Sputnik 1’s first orbits of the Earth, the Soviet Union inaugurated its Luna series of space probes. These were designed to carry packages of scientific instruments past, into orbit around and ultimately onto the surface of the Moon. This being the era of the Cold War, they were also intended to show the superiority of Soviet technology, and by reflected glory, of its political system. The program achieved many firsts, one of which we celebrate this month. On February 3, 1966, Luna 9 made the first soft landing on…

◗ Astronomers talk about three populations of stars, based on Walter Baade’s work in the 1940s studying the Milky Way. These are: • Pop I: usually young and in the galaxy’s spiral disk. Metals make up about 2–4% of their total composition. Includes both the Sun and O- and B-type, bluish massive stars. • Pop II: older (often 10 billion years or more), in the galaxy’s bulge and halo. Metal content much lower, down to maybe a thousandth that of the Sun. Only the least massive ones survive today. • Pop III: the fabled first stars. Would have formed with only hydrogen and helium (no metals). None yet conclusively detected — either they’ve died off or are masked by heavy-element ‘pollution’ they’ve picked up over time.…

China’s professional astronomical community is growing rapidly, and its researchers are planning several major new facilities both on the ground and in space. Hard X-ray Modulation Telescope (HXMT) will be China’s first orbiting X-ray observatory. Proposed by Li Tipei and Wu Mei of the Chinese Academy of Sciences’ Institute of High Energy Physics in 1993 and officially approved in 2011, HXMT will: (1) scan the galactic plane to find new transient sources and to monitor known ones, and (2) observe X-ray binaries to study the dynamics and emission mechanisms in strong gravitational or magnetic fields. HXMT carries low-, medium-and high-energy X-ray telescopes that cover energies from 1 to 250 keV. The spacecraft is complete and ready for launch. Large Optical-infrared Telescope (LOT), with an aperture of 12 m, would serve…

SPLASHES OF BRIGHT rays are among the most conspicuous lunar features. When the Moon is nearly full, the vast ray system from Tycho seems to girdle the nearside like the segment boundaries of a peeled orange. Copernicus likewise exhibits an extensive ray family, with streamers stretching halfway across Mare Imbrium. A similar but smaller system radiates from Kepler. A characteristic of all these families is that we can readily identify their source craters. But many shorter and fainter rays have ambiguous parentage. Most famous and controversial is the so-called Bessel ray, a straight, bright streak in the southern half of Mare Serenitatis that lies tangent to the 16-km-wide crater Bessel. The brightest segment of the ray is 150 km long, though less certain extensions likely double this length. A little…

PORTABLE MOUNT iOptron unveils its latest compact drive for nightscape photography, the SkyTracker Pro (US$399). The unit attaches to your photo tripod and acts as a right-ascension drive, tracking your DSLR camera for long-exposure photography. The SkyTracker Pro includes a geared alt-azimuth base, which, coupled with its precision polar finder scope, allows precise alignment in minutes. The SkyTracker Pro fits both3/ 8 and ¼-20 tripod threads, and includes an internal rechargeable battery. ioptron.com and dealers MID-SIZED CCD CAMERA QHYCCD introduces the latest model in its ‘all-in-one’ product series, the QHY16200A (US$3,999) CCD camera. Its 4,540 × 3,630 (16-megapixel) array APS-H format detector measures 27 × 21.6 mm with 6-micron-square pixels, providing high resolution in a compact area. The camera’s dual-stage thermoelectric cooling is capable of stable temperatures of 40° below…

CHAMAELEON CLOUDS Russell Cockman A small constellation, Chamaeleon is nevertheless home to some huge molecular clouds. Russell used a 130-mm refractor and SBIG STL-11000M camera for a total of 6 hours and 20 minutes LRGB exposure. BARRED SPIRAL Paul Haese NGC 1365 in Fornax is known as the Great Barred Spiral Galaxy. At its core is a 2-million-solar-mass black hole whose surface is spinning at almost the speed of light. To make this image, Paul used a GSO RC12 scope and STXL-11002 camera for a whopping total exposure of 35.4 hours LHaRGB. HANDHELD MOON Johan Henzen Demonstrating that you don’t need expensive camera gear to take decent shots, Johan took this one by simply holding his iPhone 5 up to the (25-mm) eyepiece of his 200-cm f/5 Dobsonian. ALIGNMENT NIGHT…

Two novae in Sagittarius Amateur astronomer Koichi Itagaki spotted a nova in Sagittarius on October 20th, using a 180-mm telephoto lens to take sky-patrol photos. Within two days, the explosion shot up three magnitudes to be brighter than 8.0. That put it within range of 50-mm binoculars. As of mid-November, its temporary name was TCP J18102829-2729590. Meanwhile on October 25th, the ASAS-SN automated survey and observer Yukio Sakurai turned up a second, 9.7-magnitude nova in the same region. It’s designated ASASSN-16ma. Read more at https://is.gd/sagnova2016 • BOB KING Jupiter returns with a stormy surprise Planetary observers have been treated to an outbreak in Jupiter’s North Temperate Belt (NTB). Using NASA’s Infrared Telescope Facility in Hawai‘i, Glenn Orton first noticed the series of bright spots encircling the planet on October 19th.…

A SPECTACULAR lunar occultation will occur on the night of February 11/12, when the Moon will slip in front of the star Regulus. Observers all across Australia will be able to see it, apart from those in the far north (eg. Darwin), for whom the star will appear to graze the lunar disk instead. Here are the start and end timings in the local time zones for the capital cities: Brisbane (11:41pm; 12:49pm), Sydney (12:37am, 1:57am), Canberra (12:33am, 1:56am), Hobart (12:37am, 1:58am), Melbourne (12:27am, 1:50am), Adelaide (11:42pm, 1:05am) and Perth (8:38pm, 9:50pm). Why not try your hand at some photography and send us your shots? Mercury puts on a bit of a lacklustre performance during February and March, beginning the period low in east prior to sunrise before slipping behind…

ON JANUARY 12TH, Venus reached its greatest elongation east of the Sun. Theoretically, as the Sun, Venus and Earth then formed a right triangle, Venus should have appeared exactly 50% sunlit when seen through a small telescope, a geometry known as dichotomy. However, as first noted in 1793 by German astronomer Johann Schröter, Venus looks exactly half lit on a date that does not coincide with the theoretical one. On January 12th, for example, Venus instead appeared to have already passed the point of dichotomy, instead showing a phase that is slightly concave. At western elongations, when Venus appears in the morning sky, the effect is reversed, and the observed dichotomy occurs later than predicted. Schröter, who died 200 years ago last August 29th, is no longer a household name,…

TABLETOP TELESCOPES HAVE BECOME very popular in recent years, and it’s easy to see why. Lightweight, compact, inexpensive, and easy to use — what’s not to like? The most recent entry in this field is the LightBridge Mini series, a family of three Newtonian reflectors from Meade Instruments with apertures of 82, 114 and 130 mm. The word ‘family’ is particularly appropriate in this case, because when you see all three lined up on a table, it’s hard not to think of them as Papa Scope, Mama Scope and Baby Scope. I will refer to them by those names, which seem more distinctive than Mini 130, Mini 114 and Mini 82. At first glance, they seem identical except for size, but differences emerge on closer inspection. Papa and Mama have…

FOR THE LAST 50 YEARS, every second Easter has seen amateur astronomers gather from around Australia, New Zealand and further afield for the National Australian Convention of Amateur Astronomers (NACAA). The March 2016 event was hosted by the Sutherland Astronomical Society, and held at the University of Sydney with the kind support of the Sydney Institute for Astronomy (SIfA). The Convention began on the Friday with a range of workshops and related symposia (see ‘Serious astronomy’ sidebar), but kicked off in earnest on the Saturday with a keynote address from Professor Joss Bland-Hawthorn, Director of the SIfA. Joss entertained and informed the audience in equal measure with a presentation entitled ‘Fireworks at the heart of the Galaxy’. The rest of the day was broken into parallel streams. The first focused…

Black holes vs galaxies Astronomers have discovered that galaxies and their resident massive black holes have a love/hate relationship. Small scope stargazing How much astronomy can you do if you have only a small telescope? Plenty. The sky abounds in easy celestial targets. Planet photography Recording impressive portraits of the Moon and planets is easy and inexpensive. We show you how. Taking care of your optics When and how should you clean mirrors and lenses? We ask the experts. FIND US ON FACEBOOK…