Thursday 21 April 2016

Asteroid 2016 GP221 passes the Earth.

Asteroid 2016 GP221 passed by the Earth at a distance of 592 000 km (1.54 times the average distance between the Earth and the Moon, or 0.40% of the average distance between the Earth and the Sun), slightly after 6.20 am GMT on Monday 18 April 2016. There was no danger of the asteroid hitting us, though had it done so it would have presented no threat. 2016 GP221 has an estimated equivalent diameter of 12-39 m (i.e. it is estimated that a spherical object with the same volume would be 12-39  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 btween 30 and 12 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of  2016 GP221JPL Small Body Database.

2016 GP221 was discovered on 14 April 2016 (four days before 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 GP221 implies that it was the 5540th asteroid (asteroid P221) discovered in the first half of April 2016 (period 2016 G).

2016 GP221 has a 714 day orbital period and an eccentric orbit tilted at an angle of 8.87° to the plane of the Solar System that takes it from 0.59 AU from the Sun (i.e. 59% of the average distance at which the Earth orbits the Sun, considerably inside the orbit of Venus) to 2.53 AU from the Sun (i.e. 253% of the average distance at which the Earth orbits the Sun, considerably more than the distance at which Mars 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 extremely common, with the last having occurred in May 2014 and the next predicted in March 2018. 2016 GP221 also has occasional close encounters with the planet Venus, with the next predicted in May 2051. 

See also...
 
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http://sciencythoughts.blogspot.co.uk/2016/04/asteroid-2016-fb13-passes-earth.htmlAsteroid 2016 FB13 passes the Earth.   Asteroid 2016 FB13 passed by the Earth at a distance of 474 500 km (1.23 times the average distance between the Earth and the Moon, or 0.32% of the average distance between the Earth and the Sun), slightly before 1.35 am GMT on Sunday 3 April...
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