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Australian Sky & Telescope April 2019

Australian Sky & Telescope is a world-class magazine about the science and hobby of astronomy.  Combining the formidable worldwide resources of its venerable parent magazine with the talents of the best science writers and photographers in Australia, Australian Sky & Telescope is a magazine produced specifically for the Southern Hemisphere’s astronomers.

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farewell to opportunity

JUST BEFORE THIS ISSUE WENT TO PRESS, the world learned the sad news that’s NASA’s intrepid Mars rover, Opportunity, had finally succumbed to the harsh Martian conditions and had fallen silent. The last signals from the craft were received in June 2018 after it had gone into hibernation mode from being covered by dust following one of Mars’ infamous storms. More than 1,000 signals sent between then and February 2019 failed to wake the rover, and on February 13 NASA formally announced the end of the mission. One of two craft (the other was Spirit) deposited on the Red Planet’s surface in January 2004, Opportunity had far outlived its original design lifetime (Spirit succumbed in 2010). Having spacecraft last longer than expected is not uncommon, but Opportunity did it better than…

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the milky way is warped in more ways than one

PICTURE A SPIRAL GALAXY and you probably see something like most artist illustrations of the Milky Way: a top-down view of a pinwheel. But from the side, these disk galaxies appear drastically different. For one, they’re much thinner than they are wide — the typical aspect ratio is like that of a pancake. And, like pancakes wobbling as they flip through the air, these galaxies are often warped. In 1957 radio observations first revealed a warp in the Milky Way’s disk of hydrogen gas, its reservoir of star-making materials. Since then astronomers have seen hints of this warp in other sources, including galactic pulsars, neighbourhood stars, and even in the cosmic dust floating throughout our galaxy. Now, Xiaodian Chen (Chinese Academy of Sciences) and his colleagues, including Professor Richard de Grijs at…

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voyager 2 enters interstellar space

VOYAGER 2 HAS BECOME the second probe to break through to interstellar space, mission scientists announced December 10 at a meeting of the American Geophysical Union in Washington, D.C. A plasma detector aboard Voyager 2 recorded a sharp decline in the speed of the solar wind on November 5. Around the same time, the spacecraft also saw a sharp uptick in cosmic rays — high-speed atomic particles that whiz around the galaxy — as well as an increase in the ambient magnetic field. This confluence of events gave mission scientists confidence that the probe had finally broken out of the heliosphere, a bubble of space surrounding the Sun in which the solar wind reigns supreme. This marks the second time that a spacecraft has crossed this threshold. Voyager 1 crossed the heliopause…

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chang’e 4 explores the lunar farside

THE CHINESE SPACECRAFT Chang’e 4 (named for the Chinese Moon goddess) has landed softly on the farside of the Moon — the first mission to accomplish this milestone. The spacecraft launched on December 7, 2018, and touched down in Von Kármán crater on January 3 at 2:26 UT. The 180-km-wide crater is one of the few flat areas within the South Pole-Aitken Basin. This basin was created in one of the Solar System’s largest impacts, which might have smashed through the crust and exposed the lunar mantle. Exploring this region may reveal information about the formation and structure of the Moon. The lander snapped images of the terrain around it, then the Yutu 2 rover (Chinese for ‘jade rabbit’) rolled down its ramp later that same day. The spacecraft landed around local…

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ligo and virgo discover four more black hole collisions

A RE-ANALYSIS OF DATA from the Laser Interferometer Gravitational-wave Observatory (LIGO) and the Virgo interferometer in Italy has found four new events, bringing the total number of gravitational-wave events detected so far to 11. The tally includes the most distant and most powerful black hole merger yet discovered. LIGO and Virgo announced the new events, designated GW170729, GW170809, GW170818 and GW170823, at a gravitational-wave conference on December 1, 2018. The first of these became the most massive merger detected to date — and the most distant too, as the signal had travelled 5 billion years to Earth. To create the signal, two black holes weighing in at 34 and 51 solar masses had coalesced into an 80-solar-mass monster, unleashing the energy equivalent of five solar masses as gravitational waves. The finds help…

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osiris-rex arrives, finds hints of ancient water

NASA’S OSIRIS-REX arrived at asteroid 101955 Bennu on December 3 and kept pace with the asteroid for several weeks before entering into orbit on December 31. Now, the spacecraft is mapping Bennu from about 730 metres above its surface. Even before it entered into orbit, Osiris-REX’s preliminary surveys had led to the detection of hydrated minerals on Bennu’s surface, suggesting that the asteroid’s larger parent body once hosted water. Amy Simon (NASA Goddard) announced the results December 10 at a meeting of the American Geophysical Union in Washington, D.C. Two spectrometers onboard Osiris-REX picked up the presence of hydroxyls, molecules that contain oxygen and hydrogen atoms bonded together. The mission team suspects that these molecules are locked up in clay minerals, formed in interactions with liquid water or water vapour. Bennu itself is…