Asteroid 2020 CA passed by the Earth at a distance of about 219 300
km (0.57 times the average distance between the Earth and the Moon, or
0.15% of the distance between the Earth and the Sun), slightly before 3.50 pm
GMT on Sunday 2 February 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 CA has an estimated
equivalent
diameter of 2-7 m (i.e. it is estimated that a spherical object
with
the same volume would be 2-7 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
more than 36 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2020 CA. JPL Small Body Database.
2020 CA was discovered on 1 February 2020 (the day 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 CA
implies that the asteroid was the first object (asteroid A -
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) discovered in the first half of February 2020 (period 2020 A).
2020 CA has a 302 day orbital period, with an elliptical orbit tilted at
an angle of 1.22° to the plain of the Solar System which takes in to
0.49 AU from the Sun (49% of the distance at which the Earth orbits the
Sun, and slightly more than the distance at which Mercury orbits the Sun) and out to
1.27 AU (27%
further away from the Sun than the Earth). This means that close
encounters between the asteroid and Earth are fairly common, with the
last thought to have happened in October 2018 and the next predicted
in November 2023. Although it does cross the Earth's
orbit and is briefly
further from the Sun on each cycle, 2020 CA spends most of its time
closer to the Sun than we are, and is therefore classified as an Aten
Group Asteroid.
2020 CA also
has frequent close encounters with the planets Mercury, which it last
came close to in October 2017 and is next predicted to
pass in December 2021, and Venus, which it last came close to in September 2018 and is predicted to pass again in March 2021. 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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