Wednesday 12 October 2016

Asteroid (462959) 2011 DU passes the Earth.

Asteroid  (462959) 2011 DU passed by the Earth at a distance of 5 828 000 km (15.2 times the average distance between the Earth and the Moon, or 3.90% of the average distance between the Earth and the Sun), at about 8.30 pm GMT on Thursday 6 October 2016. There was no danger of the asteroid hitting us, though had it done so it would have presented a considerable threat. (462959) 2011 DU has an estimated equivalent diameter of 130-380 m (i.e. a spherical body with the same mass would be 130-380 m in diameter), and an asteroid of this size would be expected to pass through the atmosphere and directly impact the ground with a force of 31-2500 megatons (1800-147 000 times the explosive energy of the Hiroshima bomb), causing devastation over a wide area and creating a crater roughly 4.6-7.5 km across, and resulting in global climatic problems that could last for decades or even centuries.
 
 The calculated orbit of 2016 TD. Minor Planet Center.
 
(462959) 2011 DU was discovered on 22 February 2012 by the University of Arizona's Kitt Peak-Spacewatch Project at the Steward Observatory in the Catalina Mountains north of Tucson. The designation 2011 DU implies that it was the twentieth asteroid (asteroid D) discovered in the second half of February 2011 (period 2011 D), while the designation 462959 implies that it was 462 959th asteroid ever discovered (asteroids are not given this longer designation immediately to avoid naming double or false sightings).
 
(462959) 2011 DU has a 464 day orbital period and an eccentric orbit tilted at an angle of 2.95° to the plane of the Solar System, that takes it from 0.80 AU from the Sun (i.e. 80% of the average distance at which the Earth orbits the Sun) to 1.54 AU from the Sun (i.e. 154% of the average distance at which the Earth orbits the Sun, outside the orbit of 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 close encounters between the asteroid and Earth are extremely common, with the last having occurred in December 2011 and the next predicted in April 2020. As an asteroid possibly larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (462959) 2011 DU is also classified as a Potentially Hazardous Asteroid. (462959) 2011 DU also has occasional close encounters with the planet Venus, with the last thought to have happened in August 1983 and the next predicted for December 2022.
 
See also...
 
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