Asteroid 2015 KQ120 passed by the Earth at a distance of 3 279 000 km (8.53 times the average distance between the Earth and the Moon, or 2.19% of the average distance between the Earth and the Sun), slightly after 8.35 pm GMT on Sunday 31 May 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 KQ120 has an estimated equivalent diameter of 8-27 m (i.e. it is estimated that a spherical object with the same volume would be 8-27 m in diameter), and an object of this size would be expected to explode in an airburst (an explosion caused by superheating from friction with the Earth's atmosphere, which is greater than that caused by simply falling, due to the orbital momentum of the asteroid) in the atmosphere between 35 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2015 KQ120. JPL Small Body Database.
2015 KQ120 was discovered on 22 May 2015 (nine days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2015 KQ120 implies that it was the 3016th asteroid (asteroid Q120) discovered in the second half of May 2015 (period 2015 K).
2015 KQ120 has an 709 day orbital period and an eccentric orbit tilted at an angle of 0.45° to the plane of the Solar System, which takes it from 0.98 AU from the Sun (i.e. 98% of the average distance at which the Earth orbits the Sun) to 2.13 AU from the Sun (i.e. 213% of the average distance at which the Earth orbits the Sun, considerably more than the average distance at which the planet Mars 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). This also means that close encounters between 2015 KQ120 and the Earth are quite common, with the last having occurred in August 2013 next predicted for April 2017.
See also...
Asteroid 2015 KK120 passes the Earth.Asteroid 2015 KK120 passed by the Earth at a distance of 9 323 000 km (24.3 times the average distance between the Earth and the Moon, or 6.23% of the average distance between the Earth and the Sun), slightly after 2.15 am GMT on Sunday 31...
Asteroid 2015 KH passes the Earth.
Asteroid 2015 KH passed by the Earth at a distance of 5 516 000 km (14.4 times the average distance between the Earth and the Moon, or 3.69% of the average distance between the Earth and the Sun), slightly before 1.20 pm GMT on Friday 29 May 2015. There was...
Asteroid 2015 KT154 passed by the Earth at a distance of 15 110 000 km (39.4 times the average distance between the Earth and the Moon, or 1.01% of the average distance between the Earth and the Sun), slightly before 3.00 pm GMT on Wednesday 24...
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