Sunday, 22 May 2016

Asteroid 2016 JD18 passes the Earth.

Asteroid 2016 JD18 passed by the Earth at a distance of 625 300 km (1.63 times the average distance between the Earth and the Moon, or 0.42% of the average distance between the Earth and the Sun), at about 11.25 pm on Monday 16 May 2016. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2016 JD18 has an estimated equivalent diameter of 22-68 m (i.e. it is estimated that a spherical object with the same volume would be 22-68  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 20 and 4 km above the ground, with only fragmentary material reaching the Earth's surface, though an object at the upper end of this range would explode with the equivalent energy to about 15 megatons of TNT (roughly 880 times the energy released by the Hiroshima bomb explosion), so being directly underneath it might be rather unpleasant.

 The calculated orbit of  2016 JD18JPL Small Body Database.

2016 JD18 was discovered on 8 May 2016 (eight days before its closest approach to the Earth) by the Defense Advanced Research Projects Agency's Space Surveillance Telescope. The designation 2016 JD18 implies that it was the 454th asteroid (asteroid D18) discovered in the first half of May 2016 (period 2016 J).

2016 JD18 has a 1706 day orbital period and an eccentric orbit tilted at an angle of 5.40° to the plane of the Solar System that takes it from 0.87 AU from the Sun (i.e. 87% of the average distance at which the Earth orbits the Sun) to 4.72 AU from the Sun (i.e. 472% of the average distance at which the Earth orbits the Sun, considerably more than three times the distance at which Mars orbits the Sun and slightly inside the orbit of Jupiter). 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).2016 JD18 also has occasional close encounters with the planet Jupiter, with the last calculated to have occurred in November 2013. 
See also...
http://sciencythoughts.blogspot.co.uk/2016/05/asteroid-2016-jc6-passes-earth.htmlAsteroid 2016 JC6 passes the Earth.      Asteroid 2016 JC6 passed by the Earth at a distance of 4 922 000 km (12.8 times the average distance between the Earth and the Moon, or 3.29% of the average distance between the Earth and the Sun), at about 4.25 pm GMT on Sunday 8 May 2016...
http://sciencythoughts.blogspot.co.uk/2016/05/asteroid-388495-2008-tz3-passes-earth.htmlAsteroid (388495) 2008 TZ3 passes the Earth.                                                      Asteroid (388495) 2008 TZ3 passed by the Earth at a distance of 5 046 000 km (13.1 times the average distance between the Earth and the Moon, or 3.37% of the average distance between the Earth and the...
http://sciencythoughts.blogspot.co.uk/2016/05/asteroid-2016-hd3-passes-earth.htmlAsteroid 2016 HD3 passes the Earth.    Asteroid 2016 HD3 passed by the Earth at a distance of 843 000 km (2.19 times the average distance between the Earth and the Moon, or 0.56% of the average distance between the Earth and the Sun), slightly before 6.10 am GMT on Monday 2 May...
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