Monday 22 February 2016

Asteroid 2016 DB passes the Earth.

Asteroid 2016 DB passed by the Earth at a distance of 123 900 km (0.32 times the average distance between the Earth and the Moon, or 0.08% of the average distance between the Earth and the Sun; 103 900 km above the orbit at which the satellites supporting GPS systems operate), at about 4.50 am GMT on Monday 15 February 2016. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2016 DB has an estimated equivalent diameter of 3-12 m (i.e. it is estimated that a spherical object with the same volume would be 3-12  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 more than 60 km above the ground, with only fragmentary material reaching the Earth's surface.
 The calculated orbit of  2016 DBJPL Small Body Database.
 
2016 DB was discovered on 16 February 2016 (the day after its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2016 DB implies that it was the second asteroid (asteroid B) discovered in the second half of February 2016 (period 2016 D).
2016 DB has a 313 day orbital period, with an elliptical orbit tilted at an angle of 1.53° to the plain of the Solar System which takes in to 0.61 AU from the Sun (61% of the distance at which the Earth orbits the Sun and considerably inside the orbit of the planet Venus) and out to 1.20 AU (20% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in May 2011 and the next predicted in September this year. 2016 DB also has frequent close encounters with the planet Venus, with the last thought to have occurred in September 2010 and the next predicted for Sepember 2017. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2016 DB spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. 
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