Asteroid 2014 AA passed by the Earth at a distance of about 570 km, slightly after 2.30 am GMT on Thursday 2 January 2014. This is a remarkably close pass, only about 0.2% of the distance between the Earth and the Moon, 4.4% of the Earth's diameter or 200 km higher than the orbit of the International Space Station. Despite this 2014 AA presented no threat to us, as it is calculated to be less than 3 m in diameter, and such an object would be expected to break up in the Earth's atmosphere over 45 km above the planet's surface, making it highly unlikely that even fragmentary material would reach the ground.
The calculated orbit of 2014 AA. JPL Small Body Database Browser.
2014 AA was discovered on 1 January 2014 by the University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount Lemmon in the Catalina Mountains north of Tucson. The designation 2014 AA implies that the asteroid was the 1st object discovered in the first half of January 2014 (period 2014 A).
2014 AA has a 458 day orbital period and an eccentric orbit that takes it from 0.91 AU from the Sun (i.e. 91% of the average distance at which the Earth orbits the Sun) to 1.41 AU from the Sun (i.e. 141% of the average distance at which the Earth orbits the Sun). It is therefore classed as an Apollo Group Asteroid (an asteroid that is on average further from the Sun than the Earth, but which does get closer).
See also Asteroid 2013 YB14 passes the Earth before being discovered, Asteroid 2013 YB, Asteroid 2012 CL19 passes the Earth, Asteroid 2013 XG17 passes the Earth and Asteroid 2013 XU21 passes the Earth.
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