Friday 25 December 2020

Asteroid (488490) 2000 AF205 passes the Earth.

Asteroid (488490) 2000 AF205 passed by the Earth at a distance of about 12 849  000 km (33.5 times the average distance between the Earth and the Moon, or 8.59% of the distance between the Earth and the Sun), slightly after 4.45 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. (488490) 2000 AF205 has an estimated equivalent diameter of 86-270 m (i.e. it is estimated that a spherical object with the same volume would be 86-270 m in diameter), and an object at the upper end of this range would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be about 45 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater roughly 4 km in diameter and devastation on a global scale, as well as climatic effects that would last years or even decades.

The orbit and current position of (488490) 2000 AF205. JPL Small Body Database.

(488490) 2000 AF205 was discovered on 8 January 2000 by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research Laboratory in Socorro, New Mexico. The designation 2000 AF205 implies that it was the 5031st asteroid (asteroid F205 - 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 F205 = (25 X 205) + 6 = 5031) discovered in the first half of January 2000 (period 2000 A - the year being split into 24 half-months represented by the letters A-Y, with I being excluded) while the designation 488490 implies that it was 488 490th asteroid ever discovered (asteroids are not given this longer designation immediately to avoid naming double or false sightings).

(488490) 2000 AF205 has a 384 day (1.05 year) orbital period, with an elliptical orbit tilted at an angle of 4.21° to the plain of the Solar System which takes in to 0.75 AU from the Sun (75% of the distance at which the Earth orbits the Sun, slightly outside the orbit of the planet Venus) and out to 1.32 AU (132% of the distance at which the Earth orbits the sun). 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). As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (488490) 2000 AF205 is also classified as a Potentially Hazardous Asteroid.  This means that (488490) 2000 AF205 has occasional close encounters with the Earth, with the last thought to have happened in January this year (2020) and the next predicted in January 2022.  The asteroid also has occasional close encounters with the planet Venus, which it last cam close to in November 2002 and is next predicted to pass in November 2021.
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