Thursday 17 May 2018

Asteroid 2018 JG3 passes the Earth.

Asteroid 2018 JG3 passed by the Earth at a distance of about 1 093 000 km (2.85 times the average  distance between the Earth and the Moon, or 0.73% of the distance between the Earth and the Sun), slightly before 2.30 pm GMT on Friday 11 May 2018. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2018 JG3 has an estimated equivalent diameter of 12-38 m (i.e. it is estimated that a spherical object with the same volume would be 12-38 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 30 and 12 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2018 JG3. Minor Planet Center.

2018 JG3 was discovered on 14 May 2018 (three days after 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 2018 JG3 implies that it was the 82nd asteroid (asteroid G3) discovered in the first half of May 2018 (period 2018 J).
2018 JG3 has a 777 day orbital period and an eccentric orbit tilted at an angle of 9.66° to the plane of the Solar System, which takes it from 0.81 AU from the Sun (i.e. 81% of the average distance at which the Earth orbits the Sun) to 2.49 AU from the Sun (i.e. 249% of the average distance at which the Earth orbits the Sun, and more distant 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 the asteroid has occasional close encounters with the Earth, with the last having occurred in December 2015.
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