Sunday 24 March 2019

Asteroid 2019 FA passes the Earth.

Asteroid 2019 FA passed by the Earth at a distance of about 229 900 km (0.62 times the average distance between the Earth and the Moon, or 0.15% of the distance between the Earth and the Sun), slightly before 1.15 am GMT on Saturday 16 March 2019. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2019 FA has an estimated equivalent diameter of 3-11 m (i.e. it is estimated that a spherical object with the same volume would be 3-11 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 more than 30 above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of 2019 FA. JPL Small Body Database.

2019 FA was discovered on 16 March 2018 (the day of its closest approach to the Earth) by the University of Tokyo's Kiso Observatory. The designation 2019 FA implies that the asteroid was the first object (object A - in numbering asteroids the letters A-Z, excluding I, are assigned numbers from 1 to 25, so that A = 1) discovered in the second half of March 2019 (period 2019 F).

2019 FA is calculated to have an 568 day orbital period and an eccentric orbit tilted at an angle of 1.10° to the plane of the Solar System, which takes it from 0.94 AU from the Sun (i.e. 94% of the the average distance at which the Earth orbits the Sun) to 1.74 AU from the Sun (i.e. 174% of the average distance at which the Earth orbits the Sun, more than the distance at which the planet Mars orbits). 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 the Earth are quite common, with the last calculated to have happened in June 2006 and the next predicted for November 2029. The asteroid also has occasional close encounters with the planet Mars, with the last calculated to have occurred in September 1997.

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