Asteroid 2020 TS1 passed by the Earth at a distance of about 254 600 km (0.66 times the average distance between the Earth and the Moon, or 0.17% of the distance between the Earth and the Sun), slightly before 11.00 am GMT on Monday 12 October 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 TS1 has an estimated equivalent diameter of 3-9 m (i.e. it is estimated that a spherical object with the same volume would be 3-9 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) more than 32 km above the ground, with only fragmentary material reaching the Earth's surface.
2020 TS1 was discovered on 8 October 2020 (four days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope. The designation 2020 TS1 implies that it was the 42nd asteroid (asteroid S1 - 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., which means that S1 = (24 x 1) + 18 = 42) discovered in the first half of October 2020 (period 2020 T).
2020 TS1 has a 296 day (0.81 year) orbital period, with an elliptical orbit tilted at an angle of 3.70° to the plain of the Solar System which takes in to 0.87 AU from the Sun (87% of the distance at which the Earth orbits the Sun) and out to 1.02 AU (2% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are very common, with the last thought to have happened in October 2016 and the next predicted in August 2025. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2020 TS1 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. 2020 TS also has occasional close encounters with the planet Venus, with the last having happened in April this year (2020), and the next predicted in December 2031.
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