Innholdsfortegnelse for October 2019 i Australian Sky & Telescope

NEW RESEARCH SHOWS that a dense mass lies buried under the South Pole-Aitken Basin, hidden from view on the lunar farside. It might be the remains of the impactor that formed the basin. Even though the South Pole-Aitken Basin spans roughly 2,400 kilometres, it isn’t particularly obvious in spacecraft photos. Topographically, though, it’s an unmistakable pit up to 13 kilometres deep. Geologists have long suspected that the basin formed some 4 billion years ago in a slow, shallow, and oblique collision with an object roughly 200 kilometres across. Now a team led by Peter B. James (Baylor University) has identified a huge mass buried underneath the basin, based on analysis of topographic maps from NASA’s Lunar Reconnaissance Orbiter and gravity data from NASA’s Gravity Recovery and Interior Laboratory (GRAIL) mission.…

XMM-Newton’s field of view is equivalent to the full Moon, so any given X-ray image holds an extra 50 to 100 sources that weren’t the target of the observations. After two decades, all of these extra sources add up — XMM-Newton’s Survey Science Center has now amassed 531,454 unique X-ray sources over 1,000 square degrees on the sky. The figure above shows the density of observed objects in the 8th data release of the XMM-Newton Serendipitous Source Catalogue, mapped in galactic coordinates.…

Scientists have unmasked mystery incarnate. On April 10, representatives of the Event Horizon Telescope collaboration unveiled a reconstructed image of the gargantuan black hole that squats in the heart of the giant elliptical galaxy M87. The black hole is an invisible behemoth, so large that light would take 1½ days to cross it. And it’s beautiful. “We have seen what we thought was unseeable,” said EHT director Sheperd Doeleman (Center for Astrophysics, Harvard & Smithsonian) during a National Science Foundation press conference in Washington, DC. “We have seen and taken a picture of a black hole. Here it is.” An outcome of Einstein’s equations of gravity, black holes have suffered a century of disbelief, debate and then wonder as scientists grappled with their existence. It was astronomical observations of blazing…

My favourite observations allow me to make comparisons: similar objects at different distances, or objects of different sizes at the same distance. The ‘sugar spoon’ asterism to the northeast of Sagittarius has an abundance of great objects to compare. Start with the stars at the lip of the spoon, Xi1 (ξ1) and Xi2 Sagittarii. The brighter of the two, Xi2 Sagittarii, is a K-type orange giant, 415 times as bright as our Sun, lying 370 light-years away. Xi1 Sagittarii is a bit dimmer as seen from Earth, but that appearance is misleading. This A-type bright giant is more than 3,200 times as bright as the Sun, but it’s also more than five times farther out, at 2,100 light-years. A couple of degrees to the south, the wide binocular pair Nu1 (ν1) and Nu2 Sagittarii…

I’m fortunate enough to live at Linden Observatory in the Blue Mountains west of Sydney. The Western Sydney Amateur Astronomical Group uses the location as its observing site — Google them, come visit. I mention this because I’m around a lot of observers, every one of whom (other than me it seems) has some sort of software to find their way around the sky. You’ll need it for this issue’s variable star, for our target is the (sometimes) 12th-magnitude VY Sculptoris, located 6.5 degrees east of Fomalhaut, and it’s a tough find via star hopping. I suggest starting with an eyepiece that gives at least a one-degree FOV. With 20 cm or more of aperture you’ll see the star field depicted in the chart above. According to the AAVSO, VY…

Uranus, the faintest planet visible to the naked eye, is curling westward through Aries on its way to a late October opposition. The icy, stinky planet (its cloud deck contains hydrogen sulfide) rises in the east-northeast after 9:00 pm in mid-September and culminates at about 40 degrees elevation (for mid-southern latitudes) just after 1:00 am at the beginning of October. Glowing at magnitude 5.7, Uranus is just bright enough to be viewed without optical aid under dark skies. Binoculars easily show the planet, and a small telescope at moderate magnification will expose its 3.7 arcsecond disk. With the right conditions and at higher magnifications, your telescope will also reveal a hint of cyan in the orb. If you’re not using a Go To mount, finding Uranus will require a bit…

Nominations are now open for the Berenice and Arthur Page Medal, awarded for excellence in amateur astronomy. The prize is awarded every two years by the Astronomical Society of Australia (ASA), the nation’s body of professional astronomers, for scientific contributions by an amateur astronomer that have served to advance astronomy. The Berenice Page Medal was inaugurated by the ASA in 1972 in memory of Berenice Page, an exceptional amateur astronomer and foundation member of the Society. Although most ASA members are professional astronomers, Berenice and her husband Arthur were readily accepted into the Society because of the indispensable part they played in the International Astronomical Union’s Flare Star Programme in the 1960s. Arthur Page remained an ASA member until his death in 2011 and, with his family’s agreement, the Society…

NASA’S NEW FRONTIER missions have travelled to Pluto, Jupiter and the asteroid Bennu. Now, NASA has announced that the fourth mission in this exploration lineup will head for Titan, Saturn’s largest moon. Elizabeth ‘Zibi’ Turtle (Johns Hopkins University Applied Physics Laboratory) will lead a team in designing and building Dragonfly, an eight-rotor, rover-size drone that will helicopter around the icy, eerily Earth-like world. Dragonfly will launch in 2026 for an eight-year trajectory through the Solar System before it lands among Titan’s sand dunes in 2034. From there, the drone will conduct dozens of reconnaissance flights, investigating the organics-based grains that make up the dunes before flying farther afield to approach and enter Selk Crater. A long-ago impact melted water ice there, which mixed with organic molecules, mimicking the ingredients for…

A controversial study suggests that the dwarf galaxy Antlia 2, discovered in Gaia data, had a long-ago run-in with the Milky Way galaxy. Starting back in 2009, Sukanya Chakra-barti (Rochester Institute of Technology) began fleshing out a theoretical scenario: The ripples that astronomers observe decorating our galaxy’s outskirts could have been initiated several hundred million years ago when a dwarf galaxy smashed through the Milky Way. At a meeting of the American Astronomical Society, Chakrabarti announced that the dwarf galaxy Antlia 2 might be the guilty party. The stars of Antlia 2 are spread surprisingly thin, suggesting that the dwarf might have tangled gravitationally with the Milky Way. Chakra-barti calculated its possible effects on our galaxy depending on how closely the two approached, while also considering a variety of galactic…

2,694 TOTAL PLANETS CONFIRMED as of June 2019 2,333 confirmed planets discovered by Kepler 361 confirmed planets discovered by K2 Astrophysical targets Kepler has proved to be a game-changer for astrophysics as well. Its data have enabled astronomers to peer deep within stars, track supernovae, and image planets, moons and asteroids in our own backyard. 4 SOLAR SYSTEM PLANETS 0 (Kepler), 4 (K2) 21 COMETS 0 (Kepler), 21 (K2) 67 SUPERNOVAE 6 (Kepler), 61 (K2) 81 OBJECTS BEYOND NEPTUNE 0 (Kepler), 81 (K2) 268 ASTEROIDS 0 (Kepler), 268 (K2) 644 PLANETS THAT ORBIT SUN-SIZE STARS 604 (Kepler), 40 (K2) 78,748 GALAXIES 400 (Kepler), 78,348 (K2) 530,506 STARS 200,038 (Kepler), 330,468 (K2) Is anyone there? Kepler and K2 found 31 potentially habitable planets Record setter A few of the exoplanet records…

Telescopes across the planet simultaneously record emission from near the black hole. Correlators combine the raw data, sifting out signals from noise. Team members align all the signals to within picoseconds. Data are converted to radio brightness measurements. Blind imaging stage: Teams use independent algorithm approaches to create images. Teams use different software packages to attack data systematically, producing three independent results. Three images are averaged to create a final consensus image. The team compares real data with simulated shadows, blurred to the same resolution, to deduce where the photon ring is in the fuzzy image.…

This year’s Orionid meteor shower peak on October 22 will be affected by the last quarter Moon, and the dark window between the radiant rising and moonlight interference will be limited. The shower’s radiant will be well-placed for observation after 1:00am local time. My first experience with the Orionids came in 1986 when Comet Halley graced our skies. (Halley is the parent body of the Orionids and the Eta Aquariids). I had recently become a member of the Astronomical Society of Victoria, and a group of us went to its old dark sky location in Murchison, Victoria. I recall the shower was very active that year. It stirred my imagination, and I developed a lifelong interest in meteor showers. In 2006, I planned an astro-camping weekend away to Nagambie in…

To the unaided eye, Venus is one of the most beautiful sights in the sky, outshining every celestial object except the Sun and the Moon with a pure white light. However, for telescopic observers the dazzling face of Venus is usually a disappointing sight compared with the richly detailed globes of Mars and Jupiter. An unbroken canopy of clouds overlaid by a thick layer of haze conceals the surface of Venus from prying eyes. It is not unusual for experienced observers working with powerful instruments under excellent conditions to find the planet utterly devoid of markings of any kind. When markings are visible, they are almost invariably diffuse, dusky shadings of low contrast. It’s a small wonder that three centuries of attempts by visual observers to discern patterns in the…

“You can’t give telescope time for this junk science! Who does she think she is?” blustered a young upstart upon hearing that an elderly astronomer wanted half a night with one of the brand-new Keck telescopes to observe objects that might disprove the Big Bang theory. Observatory Director Joe Miller was quick to put the youngster in his place: “You just look up Margaret Burbidge, the Margaret Burbidge, and you’ll know who she is,” he said. “If Margaret Burbidge wants half a night to draw up pictures of Mars, I’ll give it to her — whether we think it’s crazy or not, we’re going to show respect to one of the greatest astronomers of the 20th century.” Though the night turned out to be cloudy and she wouldn’t have found…

THE MIRRORLESS CAMERA WARS ARE ON. With the recent introduction of Canon’s EOS R and Nikon’s Z series, the two major camera manufacturers finally challenge Sony’s lead in the mirrorless, full-frame camera market. These new models establish the mirrorless design as the future for serious consumer cameras. Not that DSLRs, cameras that use reflex mirrors for framing and focusing, are going away anytime soon. But the new generation of mirrorless models, with their larger lens mounts and shorter required distance from lens to sensor, allow greater freedom in lens design. The camera bodies are smaller and lighter, in contrast to DSLRs that, in top-end models at least, have become larger and heavier. But are the upstart mirrorless cameras as good as our tried-and-true DSLRs for the demands of astrophotography? We…

Recently I heard from a disheartened astrophotographer. After mastering deep sky imaging with amateur equipment, he came into some money and bought a professional-grade setup, with a large Schmidt camera and a top-quality mount. He was taking beautiful images of nebulae and galaxies but found himself exhausted, bored, and frustrated. Part of his problem was the time commitment. No longer limited by his equipment, he was spending 40 hours accumulating sub-exposures for each image, then many hours processing them. And although his pictures were gorgeous, they were just like the best pictures taken by others. What, he wondered, was the purpose? The answer, I said, was to change direction and think more like a professional astronomer. In the 20th century, amateurs and professionals pulled apart. Professionals had special photographic plates,…

ASTRONOMERS HAVE HOMED IN on the host galaxies of two non-repeating fast radio bursts (FRBs), and their homes are not what the teams expected. Until recently, astronomers have only been able to identify the host galaxy of FRB 121102 — one of only two FRBs known to flash repeatedly. But on June 27, Keith Bannister (CSIRO) and colleagues reported in the journal Science that they had found the source of FRB 180924 — a millisecond-long flash that hasn’t repeated — using the 36-dish Australian Square Kilometre Array Pathfinder (ASKAP). Then, on July 2, Vikram Ravi (Caltech) and colleagues announced that they’d narrowed down the galaxy hosting a second non-repeater, FRB 190523. Both teams triangulated the sources using radio interferometry. In observations from the Dark Energy Survey, the Very Large Telescope…

A STELLAR STREAM known as GD-1 might provide evidence of a dark-matter clump in the outskirts of the Milky Way, announced Ana Bonaca (Center for Astrophysics, Harvard & Smithsonian) at a meeting of the American Astronomical Society. The finding will also appear in the Astrophysical Journal and, if it pans out, could help astronomers understand the nature of dark matter. The GD-1 stream used to be a globular cluster, but gravitational interactions with the Milky Way, starting around 3 billion years ago, pulled the group into a 30,000-light-year-long string of ‘stellar pearls’. Only, it turns out that some of the pearls are missing. Data from the European Space Agency’s Gaia satellite show two gaps in the stream, as well as a spur, where stars fly along on orbits slightly altered…

ASTRONOMY 2020 YEARBOOK Every astronomer needs the Astronomy 2020 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. Available late October — pre-order now. $29.95 plus postage & handling 2020 AUSTRALASIAN SKY GUIDE An ideal yearbook for beginners, the easy-to-read 2020 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 2020 CALENDAR Featuring amazing celestial photography from the annual David Malin Awards, the Astronomy 2020 Calendar…

WALK OUTSIDE TONIGHT and you’ll see stars twinkling in their constellations, while planets wander predictably among them. Only the occasional nova or eclipse mars the seemingly immutable heavens. But what if we swapped this tame view with X-ray vision? Hot and violent sources would flare across the sky; Aristotle would never have spoken of immutability under such a sight. Fortunately for philosophers (and for life itself), Earth’s atmosphere has long shielded against doctrine-and DNA-destroying X-rays. Humanity had graduated to space before we realised what we were missing. The first hints of an X-ray-emitting universe came from rocket and balloon observations of the Sun, starting in 1949. But solar emissions were so weak — a million times fainter than visible light — that to see even nearby stars, detectors would have…

I saw Eternity the other night, Like a great Ring of pure and endless light, All calm, as it was bright; And round beneath it, Time in hours, days, years, Driv’n by the spheres Like a vast shadow mov’d; in which the world And all her train were hurl’d. —Henry Vaughan, The World The lines of the poem above are the most famous penned by the 17th-century Welsh metaphysical poet, Henry Vaughan. The topic of those lines — and of my column this month and next — is as much about eternity as it is for our thoughts when we stare at the majesty of the Milky Way band after nightfall at winter’s end. But the topic is also time and the productions of time — for time and eternity…

Every generation of astronomers is dealt a new mystery to solve. In the late 1970s, the mystery was the discovery of a ‘star’ with very unusual properties, leading astronomers to suspect they were on to a new class of phenomena. This object, SS 433, was the 433rd listed in a 1977 catalogue of Milky Way H-alpha emission stars compiled by C. Bruce Stephenson and Nicholas Sanduleak, astronomers at Case Western Reserve University. Subsequent observations showed that its optical spectrum exhibited peculiar emission lines; it also turned out to be a variable source at radio and X-ray wavelengths. But what clinched the mystery was the discovery of an elongated feature in the radio data. This combination of properties couldn’t be reconciled to any single known model. At the time, no one…

1945 With World War II ending, Burbidge saw an opportunity to gain “access to larger telescopes, better instruments and clearer skies” in the US through an advertisement for a Carnegie Fellowship at Mount Wilson Observatory. However, her hopes were immediately dashed when her application was denied — simply on account of her gender. “A guiding operational principle in my life was activated,” she said in her 1994 memoir. “If frustrated in one’s endeavors by a stone wall … one must find a way around.” Ten years later, Geoff submitted another application, which was accepted. The couple stayed in a separate summer cottage on the mountain away from the exclusively male dormitory, and Margaret was officially only there as Geoff’s assistant. In reality, Geoff conducted the dark room work and smoked…