Saturday 17 March 2018

Asteroid 2007 LU19 passes the Earth.

Asteroid 2007 LU19 passed by the Earth at a distance of about 7 851 000 km (20.4 times the average distance between the Earth and the Moon, or 5.25% of the distance between the Earth and the Sun), slightly after 9.20 pm GMT on Saturday 10 March 2018. There was no danger of the asteroid hitting us, though were it to do so it would have presented a significant threat. 2007 LU19 has an estimated equivalent diameter of 100-330 m (i.e. it is estimated that a spherical object with the same volume would be 100-330 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 225 to 120 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 1-5 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 2007 LU19. Minor Planet Center.

2007 LU19 was discovered on 15 June 2007 by the Siding Spring Observatory near Coonabarabran in New South Wales. The designation 2007 LU19 implies that it was the 495th asteroid (asteroid U19) discovered in the first half of June 2007 (period 2007 L). 

2007 LU19 has a 1332 day orbital period and an eccentric orbit tilted at an angle of 2.60° to the plane of the Solar System, which takes it from 0.89 AU from the Sun (i.e. 89% of he average distance at which the Earth orbits the Sun) to 3.84 AU from the Sun (i.e. 384% 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 close encounters between the asteroid and Earth are extremely common, with the last having occurred in June 2007 and the next predicted in March 2029. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, 2007 LU19 is also classified as a Potentially Hazardous Asteroid.

2007 LU19 also has frequent close encounters with the planets Mars, which it last came close to in March 1960 and is next predicted to pass in May 2098, and Jupiter which it last came close to in July 1987 and is next predicted to pass in August 2022. 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.
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