Asteroid 2018 BN6 passed by the Earth at a distance of about 362 500 km (0.94 times the average distance between the Earth and the Moon, or 0.24% of the distance between the Earth and the Sun), at about 9.30 am GMT on Wednesday 24 January 2018. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2018 BN6 has an estimated equivalent diameter of 8-28 m (i.e. it is estimated that a spherical object with the same volume would be 8-28 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 18 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2018 BN6. Minor Planet Center.
2018 BN6 was discovered on 27 January 2018 (three days after 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 2018 BN6 implies that the asteroid was the 173rd object (object N6) discovered in the second half of January 2018 (period 2018 B).
2018 BN6 has a 429 day orbital period and an eccentric orbit tilted at an angle of 2.50° to the plane of the Solar System, which takes it from 0.73 AU from the Sun (i.e. 73% of he average distance at which the Earth orbits the Sun, slightly outside the orbit of Venus) to 1.49 AU from the Sun (i.e. 149% of the average distance at which the Earth orbits the Sun, and slightly inside the orbit of the planet 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). This means that the asteroid has occasional close encounters with the Earth, with the last thought to have occurred in April 2017 and the next predicted in February 2025. The asteroid also has occasional close encounters with the planet Venus, with the next predicted for 25 October 2023.
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