Sunday 13 November 2016

Asteroid 2016 VD4 passes the Earth.

Asteroid 2016 VD4 passed by the Earth at a distance of 565 900 km (1.47 times the average distance between the Earth and the Moon, 0.38% of the average distance between the Earth and the Sun), at about 5.00 am GMT on Monday 7 November 2016. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2016 VD4 has an estimated equivalent diameter of 5-18 m (i.e. it is estimated that a spherical object with the same volume would be 5-18 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 40 and 24 km above the ground, with only fragmentary material reaching the Earth's surface. 

The calculated orbit of 2016 VD4. Minor Planet Center.

2016 VD4 was discovered on 9 November 2016 (two days 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 VD4 implies that it was the 104th asteroid (asteroid D4) discovered in the first half of November 2016 (period 2016 V).
2016 VD4 has a 434 day orbital period and an elliptical orbit tilted at an angle of 11.7° to the plane of the Solar System that takes it from 0.71 AU from the Sun (i.e. 71% of the average distance at which the Earth orbits the Sun, slightly inside the orbit of Venus) to 1.25 AU from the Sun (i.e. 125% 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 means that close encounters between the asteroid and Earth are very common, with the last thought to have happened in July this year and the next predicted in May 2022.

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