Asteroid 2015 KG passed by the Earth at a distance of 5 510 000 km (14.3 times the average distance between the Earth and the Moon, or 3.68% of the average distance between the Earth and the Sun), slightly before 4.55 am GMT on Monday 18 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 KG has an estimated equivalent diameter of 7-24 m (i.e. it is estimated that a spherical object with the same volume would be 7-24 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 36 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2015 KG. JPL Small Body Database.
2015 KG was discovered on 18 May 2015 (the day of its closest approach to the Earth) 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 2015 KG implies that it was the seventh asteroid (asteroid G) discovered in the second half of May 2015 (period 2015 K).
While 2015 KG occasionally comes near to the Earth, it does not actually cross our orbital path. It has an elliptical 856 day orbit, at an angle of 0.57° to the plane of the Solar System, that takes it from 1.04 AU from the Sun (1.04 times the average distance at which the Earth orbits the Sun), slightly outside our orbit, to 2.48 AU from the Sun, (2.48 times the distance at which the Earth orbits the Sun and considerably more than the distance at which the planet Mars orbits the Sun). As a Near Earth Object that remains strictly outside the orbit of the Earth it is classed as an Amor Family Asteroid. This means that 2015KG has regular close encounters with the Earth, with the last calculated to have occurred in April 2008 and the next predicted for June 2022. 2015 KG also has occasional close encounters with the planet Mars, with the most recent having occurred in July 1923.
See also...
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