Asteroid 2020 YF passed by the Earth at a distance of about 444 300 km (1.16 times the average distance between the Earth and the Moon, or 0.30% of the distance between the Earth and the Sun),slightly after 1.20 am GMT on Friday 18 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 YF has an estimated equivalent diameter of 3-10 m (i.e. it is estimated that a spherical object with the same volume would be 3-10 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) more than 32 km above the ground, with only fragmentary material reaching the Earth's surface.
2020 YF was discovered on 17 December 2020 (the day before 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 YF 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 second half of December 2020 (period 2020 Y - the year being split into 24 half-months represented by the letters A-Y, with I being excluded).
2020 YF has a 293 day (0.8 year) orbital period, with an elliptical orbit tilted at an angle of 2.4° to the plain of the Solar System which takes in to 0.74 AU from the Sun (74% of the distance at which the Earth orbits the Sun, and slightly outside the orbit of the planet Venus) and out to 0.99 AU (99% of the distance at which the Earth orbits the Sun). As a Near Earth Object that remains strictly inside the orbit of the Earth 2020 YF is classed as an Atira Family Asteroid. This means that close encounters between 2020 YF and the Earth are very common, with the last having occured in January 2017, and the next predicted for November 2024. The asteroid also has frequent close encounters with the planet Venus, with the last having occured in June 2004 and the next predicted for April 2030.
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