Tuesday 27 March 2018

Asteroid 2018 FE3 passes the Earth.

Asteroid 2018 FE3 passed by the Earth at a distance of about 146 300 km (0.38 times the average  distance between the Earth and the Moon, or 0.01% of the distance between the Earth and the Sun), slightly after 7.10 am GMT on Monday 18 March 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 FE3 has an estimated equivalent diameter of 7-23 m (i.e. it is estimated that a spherical object with the same volume would be 7-23 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 37 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2018 FE3. Minor Planet Center.

2018 FE3 was discovered on 21 March 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 FE3 implies that it was the 80th asteroid (asteroid E3) discovered in the second half of March 2018 (period 2018 F).
2018 FE3 has a 304 day orbital period, with an elliptical orbit tilted at an angle of 6.91° to the plain of the Solar System which takes in to 0.70 AU from the Sun (70% of the distance at which the Earth orbits the Sun, roughly the distance at which Venus orbits the Sun) and out to 1.07 AU (7% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in September 2013 and the next predicted in August this year. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2018 FE3 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. This also means that the asteroid has occasional close encounters with the planet Venus, with the last calculated to have occurred in March 2007, and the next predicted for March 2021.

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