Tuesday, 21 April 2015

Asteroid 2015 HH passes the Earth.

Asteroid 2015 HH passed by the Earth at a distance of 4 513 000 km (11.7 times the average distance between the Earth and the Moon, or 3.02% of the average distance between the Earth and the Sun), slightly after 10.25 am GMT on Tuesday 14 April 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 HH has an estimated equivalent diameter of 11-36 m (i.e. it is estimated that a spherical object with the same volume would be 11-36 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 32 and 12 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of 2015 HH. JPL Small Body Database.

2015 HH3 was discovered on 16 April 2015 (twp days after its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2015 HH implies that it was the eighth asteroid (asteroid H) discovered in the second half of April  2015 (period 2015 H).

2015 HH has an 402 day orbital period and an eccentric orbit tilted at an angle of 11.5° to the plane of the Solar System, which takes it from 0.96 AU from the Sun (i.e. 96% of the average distance at which the Earth orbits the Sun) to 1.17 AU from the Sun (i.e. 117% of the average distance at which the Earth 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 HH and the Earth are quite common, with the last having occurred in October 2014 next predicted for November 2014.

See also...

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