Asteroid 2020 HC6 passed by the Earth at a distance of about 1 110 000 km (2.89 times the average distance between the Earth and the Moon, or 0.74% of the distance between the Earth and the Sun), at about 10.55 am GMT on Saturday 9 May 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 HC6 has an estimated equivalent diameter of 16-50 m (i.e. it is estimated that a spherical object with the same volume would be 16*50 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 25 and 8 km above the ground, with only fragmentary material reaching the Earth's surface.
2020 HC6 was discovered on 24 April 2020 (fifteen 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 HC6 implies that the asteroid was the 147th object (asteroid C6 - 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 L6 = (24 x 6) + 3 = 147) discovered in the second half of April 2020 (period 2020 H).
2020 HC6 has a 573 day (1.57 year) orbital period and an eccentric orbit tilted at an angle of 4.88° to the plane of the Solar System, which takes it from 0.98 AU from the Sun (i.e. 98% of he average distance at which the Earth orbits the Sun) to 1.72 AU from the Sun (i.e. 172% of the average distance at which the Earth orbits the Sun, and more than the distance at which the planet Mars orbits the Sun). 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 2020 HC6 has occassional close encounters with the Earth, with the last having happened in August 2009, and the next predicted for April 2031.
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