Saturday 11 March 2017

Asteroid 2017 DS109 passes the Earth.

Asteroid 2017 DS109 passed by the Earth at a distance of 353 300 km (0.92 times the average distance between the Earth and the Moon, 0.24% of the average distance between the Earth and the Sun), slightly before 2.30 pm GMT on Sunday 5 March 2017. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2017 DS109 has an estimated equivalent diameter of 12-38 m (i.e. it is estimated that a spherical object with the same volume would be 12-38 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 30 and 12 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2017 DS109. Minor Planet Center.

2017 DS109 was discovered on 27 February 2017 (six days after its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2017 DS109 implies that it was the 2743rd asteroid (asteroid S109) discovered in the second half of February 2017 (2017 D).

2017 D3S109 has a 1121 day orbital period and an eccentric orbit tilted at an angle of 4.16° to the plane of the Solar System, which takes it from 0.91 AU from the Sun (i.e. 91% of he average distance at which the Earth orbits the Sun) to 3.31 AU from the Sun (i.e. 3.31% of the average distance at which the Earth orbits the Sun, considerably over twice 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 close encounters between the asteroid and Earth are common, with the last having occurred in February 2014 and the next predicted in April 2020.   

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