Asteroid 2020 HF passed by the Earth at a distance of about 875 700 km (2.28 times the average distance between the Earth and the Moon, or 0.59% of the distance between the Earth and the Sun), at about 10.05 pm GMT on Thursday Saturday 18 April 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 HF has an estimated equivalent diameter of 17-55 m (i.e. it is estimated that a spherical object with the same volume would be 17-55 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 HF was discovered on 16 April 2020 (two days before its closest approach to the Earth) by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2020 HF implies that the asteroid was the sixth object (object F - in numbering asteroids the letters A-Z, 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., which means that F = 6) discovered in the second half of April 2020 (period 2020 H).
2020 HF has a 303 day orbital period, with an elliptical orbit tilted at an angle of 0.32° to the plain of the Solar System which takes in to 0.64 AU from the Sun (64% of the distance at which the Earth orbits the Sun, and inside the orbit of the planet Venus) and out to 1.13 AU (13% 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 September 2019 and the next predicted in January 2024. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2020 HF spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. The asteroid also has occasional close encounters with the planet Mercury, with the last having happened in May 2011, and the next predicted for June this year (2020).
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