The asteroid 2013 UL9 passed by the Earth at a distance of 16 190 000 km (over 42 times the distance from the Earth to the Moon), at about 3.35 pm GMT on Thursday 31 October 2013. There was no danger of the asteroid hitting us, and had it done so it would have presented only a minor threat; 2013 UL9 is calculated to be between 26 and 82 m in diameter, and such an object would be expected to break up in the atmosphere between 17 and 1 km above the ground, with only fragmentary material reaching the Earth's surface. Being directly underneath an object towards the upper end of this range would probably be fairly unpleasant, but it would not be expected to have global effects.
The calculated orbit of 2013 UL9. JPL Small Body Database Browser.
2013 UL9 was discovered on 30 October 2013 by the University of Arizona's Catalina Sky Survey in the Catalina Mountains north of Tucson. The designation 2013 UL9 implies that it was the 236th asteroid discovered in the second half of October 2013 (period 2013 U).
While 2013 UL9 occasionally comes near to the Earth, it does not actually cross our orbital path. It has an eccentric 3.86 year orbit that takes it from 1.10 AU from the Sun (1.10 times the distance at which the Earth orbits the Sun), slightly outside our orbit, to 3.8 AU from the Sun, more than twice the distance at which the planet Mars orbits the Sun; 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. 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 UR4 passes the Earth, Asteroid 2013 TY5 passed the Earth, Asteroid 2013 UU4 passes the Earth, Asteroid 2013 UQ1 passes the Earth and Asteroid 2013 TO69 passed the Earth.
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