Wednesday 18 March 2015

Asteroid 2015 FD passes the Earth.

Asteroid 2015 FD passed by the Earth at a distance of 4 212 000 km (11.0 times the average distance between the Earth and the Moon, or 2.82% of the average distance between the Earth and the Sun), slightly before 2.10 am GMT on Wednesday 11 March 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 FD has an estimated equivalent diameter of 9-30 m (i.e. it is estimated that a spherical object with the same volume would be 9-30 m in diameter), and an object of this size would be expected to break up in the atmosphere between 33 and 16.5 km above the ground, with only fragmentary material reaching the Earth's surface.

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

2015 FD was discovered on 16 March 2015 (five 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 2015 FD implies that it was the forth asteroid (asteroid D) discovered in the second half of March 2015 (period 2015 F). 

2015 FD has a 312 day orbital period, with an elliptical orbit tilted at an angle of 5.58° to the plain of the Solar System which takes in to 0.66 AU from the Sun (66% of the distance at which the Earth orbits the Sun, inside the orbit of Venus) and out to 1.14 AU (14% further away from the Sun than the Earth). As an asteroid that spends most of its time closer to the Sun than the Earth, 2015 FD is classified as an Aten Group Asteroid. This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in June 2010 and the next predicted in September this year. Close encounters between Venus and 2015 FD are also quite common, with the last calculated to have occurred in November 2008 an the next predicted for January 2020.

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