Friday 6 October 2017

Asteroid 1989 VB passes the Earth.

Asteroid 1989 VB passed by the Earth at a distance of about 3 026 000 km (7.87 times the average distance between the Earth and the Moon, or 2.02% of the distance between the Earth and the Sun), slightly after 8.00 pm GMT on Friday 29 September 2017. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 1989 VB has an estimated equivalent diameter of 200-620 m (i.e. it is estimated that a spherical object with the same volume would be 200-620 m in diameter), and an object of this size would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be 15 000-600 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 3-8 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.

 The calculated orbit of 1989 VB. Minor Planet Center.

1989 was discovered on 1 November 1989 by the Siding Spring Observatory near Coonabarabran in New South Wales. The designation 1989 VB implies that it was the second asteroid (asteroid B) discovered in the first half of November 1989 (period 1989 V). 

1989 VB has a 929 day orbital period and an eccentric orbit tilted at an angle of 2.13° to the plane of the Solar System, which takes it from 1.00 AU from the Sun (i.e. 100% of he average distance at which the Earth orbits the Sun) to 2.72 AU from the Sun (i.e. 2.72% of the average distance at which the Earth orbits the Sun, or considerably more than the distance at which the planet Mars orbits the Sun). It is therefore classed as an Amor Group Asteroid (an asteroid which comes close to the Earth, but which is always outside the Earth's orbit).As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 1989 VB is also classified as a Potentially Hazardous Asteroid. Close encounters between the 1989 VB and Earth are extremely common, with the last thought to have happened in July 2012 next predicted in November 2022. The asteroid also has occasional close encounters  with the planet Mars, with the last thought to have happened in May 1972, and the next predicted for May 2066.

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