(517103) 2013 EM20 (also designated 2008 AO112) is an Apollonear-Earth asteroid and potentially hazardous object.[2] It was discovered on 12 January 2008 by the Mount Lemmon Survey at an apparent magnitude of 21 using a 1.5-meter (59 in) reflecting telescope.[1] The asteroid was quickly lost and had an estimated diameter of 310 meters (1,020 ft).[3] On 25 June 2009, with an observation arc of only 1 day in January 2008, the asteroid had a 1 in 4 million chance of impacting Earth on that very day.[3] The virtual impactor had not been eliminated from the Sentry Risk Table by the day of the potential impact.
The asteroid was recovered on 5 March 2013 as 2013 EM20.[4]Precovery images from 7 April 1997 at Kitt Peak National Observatory were located.[2] It was removed from the Sentry Risk Table on 30 March 2013.[5] It is now known that on 25 June 2009 the asteroid was 1.45 AU from Earth.[6]
