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.
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.
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