Australian Sky & Telescope October 2015

I’m writing this editorial in August, a month that I’ve sort of come to dread, and chances are you know why. It’s because of that crazy email that does the rounds every year, claiming that Mars will make a close approach to Earth and appear as large in the sky as the full Moon. I’m sure you’ve seen it. All month long I receive phone call after phone call from friends, family, colleagues and the media, all of them wanting to know when and where they can see it. They sound so disappointed when I tell them that it’s bogus, and that Mars will not do as advertised and rival the Moon. It’s almost as if — oh, I don’t know — that they expect everything they see and hear…

Two projects are mapping the distribution of dark matter in the universe, probing scales both large and small. One, the Dark Energy Survey, is tackling the large-scale universe using the Dark Energy Camera, a 570-megapixel CCD camera that’s surveying a huge, 5,000-square-degree swath of the southern sky. Using preliminary data that covers just 3% of the full survey, Vinu Vikram (Argonne National Laboratory) and colleagues examined the shapes of more than 1 million faraway galaxies, whose light has travelled between 5.8 billion and 8.5 billion years to reach us. The team was looking for the smearing effect of intervening dark matter, which acts as a gravitational lens to magnify and distort distant galaxies’ light. Using the observed smearing, Vikram’s team constructed a 2D dark matter map (shown at right) and…

Using measurements from NASA’s Lunar Atmosphere and Dust Environment Explorer (LADEE) spacecraft, Mihaly Horanyi (University of Colorado, Boulder) and colleagues have revealed the distribution, origin and size of clouds of dust particles that float above the Moon’s surface at dawn and dusk. These dust clouds were discovered in 1968, when NASA’s last robotic lunar lander, Surveyor 7, took images of a strange twilight glow along the lunar horizon. The glow comes from light scattering off fine dust particles. LADEE’s measurements reveal that the dust cloud is much closer to the Moon’s surface and less dense than previously thought. They also confirmed the dust’s origin: comets. LADEE recorded an asymmetric dust cloud instead of a circular one along the Moon’s day-night line. If the dust is coming from asteroids, as was…

The spacecraft orbiting Comet 67P/Churyumov-Gerasimenko has found 18 holes in the nucleus. (And no, mission planners didn’t think to pack golf clubs.) ESA’s Rosetta spacecraft has been orbiting Comet 67P since August 2014, gathering observations of the funny-looking nucleus, which is shaped rather like a dog’s head. The observing campaign has turned up the new 18 pits. They’re not the first holes seen on comet nuclei, but they are the first that look like this. The pits tend to cluster together in small groups, and they range from 50 to 310 metres wide. Some pits are cylindrical and deep; others are shallow. The deep ones seem to be ‘active’ with dusty jets spewing from their walls or floors. The deepest one reaches more than 200 metres below the surface. The…

After seven months of electronic hibernation, Philae awakened on the surface of Comet 67P/Churyumov-Gerasimenko in mid-June and resumed contact with its handlers on Earth. When last heard from, early on November 15, 2014, the European Space Agency’s washing-machine-size lander had survived an unexpectedly rough-and-tumble arrival on the comet’s surface. Its transmissions ended prematurely, after only 57 hours, because Philae had wedged itself in a heavily shadowed location that offered little direct sunlight to recharge its onboard batteries. But the comet’s changing solar geometry eventually provided much more sunlight, enough to revive Philae’s basic functions. About 85 seconds of telemetry, relayed via the lander’s comet-orbiting mother ship, Rosetta, reached Earth on June 13th at 20:28 Universal Time. Then the lander inexplicably went silent again, despite multiple attempts to restore contact, until…

The supermassive black hole CID-947 is at least 10 times too massive for its host galaxy, raising questions about how closely galaxies and black holes actually coevolve. On average, a supermassive black hole has a mass 1/100 to 1/1000 that of its host galaxy. This consistent relationship has led astronomers to suspect that a black hole’s growth and that of its host galaxy are intertwined. But shining at us from a mere 2 billion years after the Big Bang, CID-947 has 1/8 its galaxy’s mass. To look like black hole–galaxy systems we see today, the galaxy would have to grow by maybe another factor of 10, without the black hole growing at all, Benny Trakhtenbrot (ETH Zurich, Switzerland) and colleagues report in the journal Science. If so, that would suggest…