Wednesday 26 December 2018

Asteroid 2012 MS4 passes the Earth.

Asteroid 2012 MS4 passed by the Earth at a distance of about 12 249 000 km (31.9 times the average distance between the Earth and the Moon, or 8.19% of the distance between the Earth and the Sun), slightly before 10.00 pm GMT on Thursday 20 December 2018. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2012 MS4 has an estimated equivalent diameter of 340-1100 m (i.e. it is estimated that a spherical object with the same volume would be 340-1100 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 between 880 and 3 000 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater between 5 and 15 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 2018 EB Minor Planet Center.

2012 MS4 was discovered on 19 June 2012 by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research Laboratory in Socorro, New Mexico. The designation 2012 MS4 implies that it was the 118th asteroid (asteroid S4) discovered in the second half of June 2012 (period 2012 S4).

2012 MS4 has a 1245 day orbital period and an eccentric orbit tilted at an angle of 67.7° to the plane of the Solar System, which takes it from 0.63 AU from the Sun (i.e. 63% of he average distance at which the Earth orbits the Sun, inside the orbit of the planet Venus) to 3.90 AU from the Sun (i.e. 390% of the average distance at which the Earth orbits the Sun, and more than twice as distant from the Sun than the planet Mars). 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 the asteroid has occasional close encounters with the Earth, with the last having occurred in June 2012 and the next predicted in June 2029. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2012 MS4 is also classified as a Potentially Hazardous Asteroid.  

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