2006 AM4 was discovered by the Mount Lemmon Survey (University of Arizona) on January 8, 2006. The asteroid will approach within 0.013 AU (5.2 lunar distances) on February 1. Its physical properties are unknown, but its absolute magnitude of 21.8 suggests a diameter within a factor of two of 140 meters. Goldstone and Arecibo are scheduled to observe the asteroid as it heads to its closest approach of 5.2 lunar distances on February 1st.
Update on January 29: Photometry reported by Carl Hergenrother and Mike Hicks indicate that 2006 AM4 is an extremely rapid rotator with a period of about 5 minutes or 12 minutes. It is among the most rapidly rotating near-Earth asteroids we have ever tried to observe with radar. In addition, photometric colours reported by Hicks indicate a Q-type taxonomic class. Due to the proximity of its orbit to Earth and its diameter, 2006 AM4 has been classified as a "Potentially Hazardous Asteroid" by the Minor Planet Centre.
