Remember to Duck Wednesday Morning
January 11, 2010 5 Comments
A very small, newly discovered asteroid will make a close flyby of Earth this Wednesday. 2010 AL30 was first seen by the LINEAR survey (same group that discovered the unusual comet P/2010 A2) on Jan 10 UT. The asteroid will pass ~80,000 miles or 128,000 km (0.00086 AU) from Earth at ~12:45 UT on Jan 13 (Wednesday morning).
With an absolute magnitude of 27.0, the asteroid is probably on the order of 10 to 20 meters in diameter. Though it will safely miss the Earth, even if it were to hit it would be unlikely to do any damage as very little of it would survive passage through the atmosphere. A recent paper by Peter Brown (University of Western Ontario) determined the rate of impact for small asteroids based on global infrasound observations. An object 15 meters in diameter should hit the Earth once every ~50 years. Based on that statistic the detection of an object like 2010 AL30 should be rare. But the Earth is a small target. Extrapolating the Earth collisional volume to the volume of space within the distance of the Moon finds that ~600 objects of the size of 2010 AL30 pass within a lunar distance every year. These kinds of close approaches are not rare, and the great majority of them are missed by the current asteroid surveys which are optimized to find much larger (and actually dangerous) objects.
The orbit of 2010 AL30 is a typical near-Earth asteroid orbit (see the diagram below). It stretches from 0.70 to 1.30 AU from the Sun. With a semi-major axis of 1.001 AU, its orbital period is almost exactly the same as Earth’s. At its brightest the asteroid will reach magnitude ~14 which is far too faint to be seen by all but the most well equipped amateurs.