Asteroid 2020 DA1 passed by the Earth at a distance of about 193 600 km (0.50 times the average distance between the Earth and the Moon, or 0.13% of the distance between the Earth and the Sun), slightly after 10.30 am GMT on Tuesday 18 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 DA1 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 DA1 was discovered on 17 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 DA1 implies that the asteroid was the 25th 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 Second half of February 2020 (period 2020 D).
2020 DA1 has a 455 day orbital period and an eccentric orbit tilted at an angle of 7.89° to the plane of the Solar System, which takes it from 0.49 AU from the Sun (i.e. 49% of he average distance at which the Earth orbits the Sun, slightly outside the orbit of the planet Mercury) to 1.81 AU from the Sun (i.e. 181% of the average distance at which the Earth orbits the Sun, and considerably 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 occasionally occur, with the last having occurred in October 2012, and the next predicted for August 2021. 2020 DA1 also has occasional close encounters with the planet Venus, with the last having happened in June 1926 and the next predicted for September 2027.
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