Asteroid 2013 UT3 passed by the Earth at a distance of 930 300 km (a little over 2.4 times the distance to the Moon), at about 8.55 am on Monday 21 October 2013. There was no danger of the asteroid hitting us, and if it had then it would have presented little threat, 2013 UT3 is estimated to be between 7 and 23 m in diameter, and such an object would be predicted to break up in the atmosphere between 20 and 36 km above the ground, with only fragmentary material reaching the Earth's surface.
2013 UT3 was discovered on 24 October 2013 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 2013 UT3 implies that the asteroid was the 94th object discovered in the second half of October 2013 (period 2013U).
2013 UT3 has a 689 day orbital period and an eliptical orbit that takes it from 0.67 AU from the Sun (i.e. 67% of the average distance at which the Earth orbits the Sun, slightly inside the orbit of Venus) to 2.38 AU from the Sun (i.e. 238% of the average distance at which the Earth orbits the Sun, outside the orbit of Mars). 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 SL20 passes the Earth, Asteroid 2013 TX68 passes the Earth, Asteroid 2013 TT5 passes by the Earth, Asteroid 2013 TL127 flies past the Earth and Asteroid 2013 RN9 to fly past the Earth on Wednesday 9 October 2013.
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