Asteroid 2020 FD passed by the Earth at a distance of about 256 600
km (0.67 times the average distance between the Earth and the Moon, or
0.17% of the distance between the Earth and the Sun), at about 4.05 am
GMT on Wednesday 18 March 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 FD has an estimated
equivalent
diameter of 6-18 m (i.e. it is estimated that a spherical object
with
the same volume would be 6-18 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
between 40 and 23 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2020 FD. JPL Small Body Database.
2020 FD was discovered on 16 March 2020 (two days before its closest encounter with the Earth) by the
University of Arizona's Mt. Lemmon Survey at the Steward Observatory on Mount
Lemmon in the Catalina Mountains north of Tucson. The designation 2020 FD
implies that the asteroid was the fourth object (asteroid D -
in numbering asteroids the letters A-Y, excluding I, are assigned
numbers from 1 to 24, with a number added to the end each time the
alphabet is ended, so that A = 1, A1 = 25, A2 = 49, etc, so that D = 4) discovered in the second half of March 2020 (period 2020 F).
2020 FD has a 487 day orbital period and an eccentric orbit
tilted at an angle of 1.17° to the plane of the Solar System, which
takes it from 0.62 AU from the Sun (i.e. 62% of he average distance at
which the Earth orbits the Sun, and inside the orbit of the planet Venus) to 1.80 AU from the Sun (i.e. 180% of
the
average distance at which the Earth orbits the Sun, and outside 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). This means that close
encounters between the asteroid and Earth are fairly common, with the
last having occurred in October 2017 and the next predicted
in March 2024.
2020 FD also
has frequent close encounters with the planets Venus, which it last passed in November 2014 is next predicted to
pass in September 2021, and Mars, which it last passed in April 2006 is predicted to pass in September 2024. 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.
See also...
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