Sunday 20 December 2020

Asteroid 2001 YV3 passes the Earth.

Asteroid 2001 YV3 passed by the Earth at a distance of about 10 969  000 km (28.6 times the average distance between the Earth and the Moon, or 7.33% of the distance between the Earth and the Sun), slightly before 3.25 pm GMT on Sunday 23 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. 2001 YV3 has an estimated equivalent diameter of 170-540 m (i.e. it is estimated that a spherical object with the same volume would be 170-540 m in diameter), and an object of this size 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 10 000-600 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater roughly 1.5-7.5 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 2001 YV3. JPL Small Body Database.
2001 YV3 was discovered on 22 December 2001 by the Air Force Maui Optical Station telescope at the the University of Hawaii's Haleakala Observatories. The designation 2001 YV3 implies that it was the 96h asteroid (asteroid V3 - 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 V3 = (25 x 3) + 21 = 96) discovered in the second half of December 2001 (period 2001 Y - the year being split into 24 half-months represented by the letters A-Y, with I being excluded).
2001 YV3 has a 992 day (2.72 year) orbital period, with an elliptical orbit tilted at an angle of 5.20° to the plain of the Solar System which takes in to 0.55 AU from the Sun (55% of the distance at which the Earth orbits the Sun, between the orbits of the planets Mercury and Venus) and out to 3.34 AU (334% of the distance at which the Earth orbits the sun, and more than twice the orbit of the planet Mars). 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, 2001 YV3 is also classified as a Potentially Hazardous Asteroid.

This means that 2001 YV3 has occasional close encounters with the Earth, with the last thought to have happened in August 2012 and the next predicted in May 2022. The asteroid also has occasional close encounters with the planets Venus, which it last cam close to in January 2018 and is next predicted to pass in April 2045, and Mars, which it last came close to in August 2015, and is expected to pass again in February 2040. Asteroids which make close passes to multiple planets are considered to be in unstable orbits, and are often eventually knocked out of these orbits by these encounters, either being knocked onto a new, more stable orbit, dropped into the Sun, knocked out of the Solar System or occasionally colliding with a planet.

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