Asteroid 2020 XF passed by the Earth at a distance of about 88 700 km (0.23 times the average distance between the Earth and the Moon, 0.06% of the distance between the Earth and the Sun, or roughly two and a half times at which geostationary satellites orbit the Earth), at about 9.00 am GMT on Thursday 3 December 2020. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2020 XF has an estimated equivalent diameter of 9-28 m (i.e. it is estimated that a spherical object with the same volume would be 9-28 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) between 33 and 18km above the ground, with only fragmentary material reaching the Earth's surface.
2020 XF was discovered on 5 December 2020 (the day 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 2020 XF implies that it was the sixth asteroid (object F - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 25, with a number added to the end each time the alphabet is ended so that A = 1, A1 = 26, A2 = 51, etc., which means that F implies the sixth asteroid F = 6) discovered in the first half of December 2020 (period 2020 X - the year being split into 24 half-months represented by the letters A-Y, with I being excluded).
2020 XF has a 317 day (0.87 year) orbital period, with an elliptical orbit tilted at an angle of 1.01° to the plain of the Solar System which takes in to 0.80 AU from the Sun (80% of the distance at which the Earth orbits the Sun) and out to 1.14 AU (114% of the distance at which the Earth orbits the Sun, and more than the distance at which the planet Mars orbits the Sun). Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2020 XF spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. Close encounters between 2020 XF and Earth are fairly common, with the last thought to have happened in February 2015 and the next predicted in April next year (2021). 2020 XF also has occasional close encounters with the planet Venus, with the last thought to have happened in February 2018 and the next predicted in April 2022.
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