Asteroid 2004 BL86 has a small companion moon!
Meteorologist/Science Writer
Monday, January 26, 2015, 6:19 PM - Astronomers took the opportunity to examine a massive asteroid with radar, as it passed by us at a safe distance, and they were rewarded in a very special way.
When asteroid 2004 BL86 swung by Earth on Monday - with more than enough room to spare, at roughly 3 times the distance to the Moon - astronomers at NASA's Goldstone Deep Space Communications Complex aimed the big 70-metre antenna there at it, bouncing radio waves off the asteroid to get a better idea of its size, shape and rate of rotation, and possibly even its composition. What they didn't count on, though, is discovering that the asteroid has a companion, in the form of a small moon!
Asteroid 2004 BL86 and its 'tiny' companion. Credit: NASA/JPL-Caltech
RELATED: Asteroid 2004 BL86 makes close pass by Earth; closest pass of large asteroid for the next 13 years
According to a NASA JPL news release:
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| The 20 individual images used in the movie were generated from data collected at Goldstone on Jan. 26, 2015. They show the primary body is approximately 1,100 feet (325 meters) across and has a small moon approximately 230 feet (70 meters) across. In the near-Earth population, about 16 percent of asteroids that are about 655 feet (200 meters) or larger are a binary (the primary asteroid with a smaller asteroid moon orbiting it) or even triple systems (two moons). |
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Although referred to as small, that's really only in relation to 2004 BL86 itself. A 70-metre wide boulder is huge, and would be classified as an asteroid unto itself (rather than a meteoroid), if it was on its own. For comparison, the chunk of rock that exploded in the atmosphere over Cheyabinsk, Russia back in February 2013 was estimated at 20 metres wide.
Interested in seeing how radio telescopes, which usually just receive signals from space, manage to take images of passing objects? Emily Lakdawalla, Senior Editor and Planetary Evangelist for The Planetary Society, explains it on their website (click here).
