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Explanation: Sweeping through northern skies, Comet Catalina (C/2013 US10) made its closest approach on January 17, passing about 6 light-minutes from our fair planet. Dust and ion tails clearly separated in this Earth-based view, the comet is also posed for a Messier moment, near the line-of-sight to M101, grand spiral galaxy in Ursa Major. A cosmic pinwheel at the lower left, M101 is nearly twice the size of our own Milky Way galaxy, but some 270 thousand light-centuries away. Both galaxy and comet are relatively bright, easy targets for binocular-equipped skygazers. But Comet Catalina is now outbound from the inner...

Explanation: A new year's treat for binoculars, as 2016 begins Comet Catalina (C/2013 US10) now sweeps through planet Earth's predawn skies near bright Arcturus, alpha star of Bootes. But this telescopic mosaic from December 21 follows the pretty tails of the comet across a field of view as wide as 10 full moons. The smattering of distant galaxies and faint stars in the background are in the constellation Virgo. Trailing behind the comet's orbit, Catalina's dust tail fans out below and left in the frame. Its ion tail is angled toward the top right, away from the Sun and buffeted...

The first of the new large near-Earth asteroid discoveries is named 2013 UQ4, and it is perhaps the most unusual. This approximately 19-kilometer (12-mile) wide object was spotted by the Catalina Sky Survey on Oct. 23 when the asteroid was 435 million kilometers (270 million miles) away from Earth. Not only is this object unusually large, it follows a very unusual highly inclined, retrograde orbit about the Sun, which means it travels around the Sun in the opposite direction of all the planets and the vast majority of asteroids. The only objects usually found in retrograde orbits are comets, which...