Asteroid 2020 KW passed by the Earth at a distance of about 483 100 km (1.26 times the average distance between the Earth and the Moon, or 0.32% of the distance between the Earth and the Sun), at about 0.55 am GMT on Saturday 18 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 KW has an estimated equivalent diameter of 4-12 m (i.e. it is estimated that a spherical object with the same volume would be 4-12 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 43 and 30 km above the ground, with only fragmentary material reaching the Earth's surface.
2020 KW was discovered on 18 May 2020 (the day of its closest approach to the Earth) by the Zwicky Transient Facility at Palomar Observatory in California. The designation 2020 KW implies that it was the 22nd asteroid (asteroid W - 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 W = 22) discovered in the Second half of May 2020 (period 2020 K - the year being split into 24 half-months represented by the letters A-Y, with I being excluded).
2020 KW has a 1072 day (2.94 year) orbital period, with an elliptical orbit tilted at an angle of 2.27° to the plain of the Solar System which takes in to 1.01 AU from the Sun (101% of the distance at which the Earth orbits the Sun) and out to 3.09 AU (309% of the distance at which the Earth orbits the sun and slightly more than twice as from the Sun as the planet Mars). This means that close encounters between the asteroid and Earth happen occasionally, with the next predicted in March 2023. It is therefore classed as an Amor Group Asteroid (an asteroid which comes close to the Earth, but which is never closer to the Sun than the Earth is).
Follow Sciency Thoughts on Facebook.