Saturday, 28 July 2018

Asteroid 2015 AM45 passes the Earth.

Asteroid 2015 AM45 passed by the Earth at a distance of about 12 394 000 km (40.0 times the average distance between the Earth and the Moon, or 10.3% of the distance between the Earth and the Sun), slightly after 9.40 am GMT on Sunday 22 July 2018. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2015 AM45 has an estimated equivalent diameter of 75-240 m (i.e. it is estimated that a spherical object with the same volume would be 75-240 m in diameter), and an object at the upper end of this range 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 32 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 3.5 km in diameter and devastation on a global scale, as well as climatic effects that would last years or even decades.

 The calculated orbit of 2015 AM45. Minor Planet Center.

2015 AM45 was discovered on 15 January 2015  by the University of Hawaii's PANSTARRS telescope. The designation 2015 AM45 implies that the asteroid was the 1137th object (object M45) discovered in the first half of January 2015 (period 2015 A).

2015 AM45 has an 706 day orbital period and an eccentric orbit tilted at an angle of 5.58° to the plane of the Solar System, which takes it from 0.75 AU from the Sun (i.e. 75% of he average distance at which the Earth orbits the Sun, slightly outside the orbit of the planet Venus) to 2.35 AU from the Sun (i.e. 235% of the average distance at which the Earth orbits the Sun, and further from the Sun as 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 September 2016 and the next predicted in January 2040. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2017 TE5 is also classified as a Potentially Hazardous Asteroid.

2015 AM45 also has frequent close encounters with the planets Venus, which it is thought to have last passed in February 2007, and which it is next predicted to pass in October 2074, and Mars, which it last came close to in May this year and is next predicted to pass in February 2066. Asteroids which make close passes to multiple planets are considered to be in unstable orbits, and are often eventually knocked out of these orbits by these encounters, either being knocked onto a new, more stable orbit, dropped into the Sun, knocked out of the Solar System or occasionally colliding with a planet.
 
See also...
 
https://sciencythoughts.blogspot.com/2018/07/the-delta-aquarid-meteors.htmlhttps://sciencythoughts.blogspot.com/2018/07/asteroid-2018-nm-passes-earth.html
https://sciencythoughts.blogspot.com/2018/07/asteroid-2018-nu-passes-earth.htmlhttp://sciencythoughts.blogspot.com/2018/07/fragment-of-asteroid-2018-la-found-in.html
http://sciencythoughts.blogspot.com/2018/07/asteroid-2018-nh-passes-earth.htmlhttp://sciencythoughts.blogspot.com/2018/07/asteroid-2018-mg7-passes-earth.html
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