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Asteroid (99942) Apophis

17 Dec 2012, 23:05 UTC
Asteroid (99942) Apophis
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Asteroid (99942) Apophis was discovered on 2004 June 19 by R. A. Tucker, D. J. Tholen and F. Bernardi at Kitt Peak and then lost until it was serendipitously recovered in December of 2004. This Aten class asteroid, approximately 270 meters in diameter, caused a brief period of concern in December 2004 because initial observations indicated a small probability that it would strike the Earth in 2029. Thanks to additional observations, the 2029 threat was eventually ruled out. However, a possibility remained that during the 2029 close encounter with Earth, Apophis would pass through a gravitational keyhole, a precise region in space no more than about a 600 meters wide, that would set up a future impact on 2036. The principal source of uncertainty is the acceleration due to the Yarkovsky effect, a non-gravitational effect that is a function of the asteroid's rotation period, pole direction, thermal properties, mass, shape, and dimensions. So this asteroid continues to receive considerable attention from amateur and professional astronomers. Apophis became (on 2004) the first object rated level 2 on the Torino scale, and for only a short time it was subsequently upgraded to level 4, the record for highest Torino rating. Currently Apophis ...

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