Sunday 27 November 2016

Asteroid 2016 WH passes the Earth.

Asteroid 2016 WH passed by the Earth at a distance of 900 100 km (2.34 times the average distance between the Earth and the Moon, 0.60% of the average distance between the Earth and the Sun), at about 0.05 am GMT on Monday 21 November 2016. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2016 WH 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 37 and 20 km above the ground, with only fragmentary material reaching the Earth's surface. 

The calculated orbit of 2016 WH. Minor Planet Center.

2016 WH was discovered on 19 November 2016 (two days before 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 2016 WH implies that the asteroid was the eigtht object (object H) discovered in the second half of November 2016 (period 2016 W).

2016 WH is calculated to have a 741 day orbital period and an elliptical orbit tilted at an angle of 2.74° to the plain of the Solar System that takes it from 0.84 AU from the Sun (i.e. 84% of the average distance at which the Earth orbits the Sun) to 2.36 AU from the Sun (i.e. 236% of the average distance at which the Earth orbits the Sun, more than the 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 means that it has occassional close encounters with the Earth, with the last having occured in November 2014.

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