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Near-Earth asteroid flyby

Submitter: Cees Bassa
Description: On January 26th an asteroid by the name of 2004 BL86 flew by the Earth. There was no danger of it impacting, as the closest distance during the flyby was 1.2 million km (3.1 lunar distances). Even though the asteroid is small, it is estimated to be about 325m in diameter, the close proximity meant it was visible as 9th magnitude star, moving between the stars at about 2.5 degrees per hour. At 9th magnitude the asteroid was easily visible in small telescopes or binoculars.

The close approach to Earth allowed radar observations with the Goldstone and Arecibo telescopes. These confirmed that the asteroid has a small moon. The existence of the small moon was reported earlier by Joe Pollock and Petr Pravec based on optical lightcurves of the asteroid.

This composite image of 15 10s exposures shows the movement of 2004 BL86 with respect to the stars. A DSLR and a fast lens were used to take the images. Besides the asteroid two geostationary satellites are also visible.
Copyright: Cees Bassa
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