(517103) 2013 EM20 explained

Background:
  1. FFC2E0
Discoverer:Mt. Lemmon Survey
Discovered:12 January 2008
Epoch:18 April 2013 (JD 2456400.5)
Uncertainty:1
Aphelion:1.808 AU (Q)
Perihelion:0.9352 AU (q)
Semimajor:1.372 AU (a)
Eccentricity:0.3182
Period:1.61 yr
Inclination:8.359°
Asc Node:73.98°
Mean Anomaly:100.4° (M)
Arg Peri:350.0°
Dimensions:~310m (1,020feet)
Mass:4.1 kg (assumed)
Abs Magnitude:19.9

(also designated ) is an Apollo near-Earth asteroid and potentially hazardous object. It was discovered on 12 January 2008 by the Mount Lemmon Survey at an apparent magnitude of 21 using a 1.5adj=onNaNadj=on reflecting telescope. The asteroid was quickly lost and had an estimated diameter of 310m (1,020feet). 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. 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 . Precovery images from 7 April 1997 at Kitt Peak National Observatory were located. It was removed from the Sentry Risk Table on 30 March 2013. It is now known that on 25 June 2009 the asteroid was 1.45 AU from Earth.