The asteroid 2010 SG15 passed by the Earth at a distance of 13 430 000 km (a little under 35 times the distance between the Earth and the Moon), slightly before 6.00 pm GMT on Sunday 13 October 2013. There was no danger of the asteroid hitting us, and even if it had it would have presented only a minor hazard; 2010 SG 15 is estimated to be between 18 and 57 m in diameter, and an object of this size would be expected to break up in the atmosphere between 23 and 8 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2010 SG15. JPL Small Body Database Browser.
2010 SG15 was discovered on 29 September 2010 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 2010 SG15 implies that it was the 382nd object discovered in the second half of September 2010 (period 2010 S).
While 2010 SG15 regularly comes near to the Earth, it does not actually cross our orbital path. It has an elliptical three year orbit that takes it from 1.08 AU from the Sun (1.08 times the distance at which the Earth orbits the Sun), slightly outside our orbit to 3.07 AU from the Sun, roughly twice as far from the Sun as the planet Mars, so unless an encounter with another body causes it's orbital path to alter in a very specific way (highly unlikely) there is no chance of it hitting the Earth. Because the orbital period of 2010 SG15 is very close to three times that of the Earth, close encounters with the Earth are quite predictable. It has passed close to us every third October since 2001 (prior to which it passed us every third November) and is predicted to continue to do so till October 2025, after which it will pass us every third September. As a Near Earth Object that remains strictly outside the orbit of the Earth it is classed as an Amor Family Asteroid.
See also Asteroid 2013 TQ135 flies past the Earth, Asteroid 2013 SE21 passes the Earth, Asteroid 2013 SR passes the Earth, Asteroid 2013 TH69 passes by the Earth and Asteroid 2013 SU19 to fly by the Earth on Thursday 10 October 2013.
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