Asteroid 2018 WE1 passed by the Earth at a distance of about 107 000 km (0.28 times the average distance between the Earth and the Moon, or 0.07% of the distance between the Earth and the Sun), slightly midnight GMT on Tuesday 25 November 2018. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2018 WE1 has an estimated equivalent diameter of 11-36 m (i.e. it is estimated that a spherical object with the same volume would be 11-36 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 30 and 12 km above the ground, with only fragmentary material reaching the Earth's surface.
2018 WE1 was discovered on 26 November 2018 (the day after its closest approach to the Earth) by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2018 WE1 implies that the asteroid was the thirtieth object (object E1) discovered in the second half of November 2018 (period 2018 W).
2018 WE1 has an 419 day orbital period and an eccentric orbit tilted at an angle of 6.27° to the plane of the Solar System, which takes it from 0.70 AU from the Sun (i.e. 70% of he average distance at which the Earth orbits the Sun and roughly the distance at which Venus orbits) to 1.49 AU from the Sun (i.e. 149% of the average distance at which the Earth orbits the Sun, almost as far from the Sun as 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). As such the asteroid has occasional close encounters with the planet Earth, which it last came close to in January this year, and is expected to pass again in April 2024. The asteroid also has occasional close encounters with the planet Venus, which it last came close to in October this year and is next predicted to pass in November 2027.
Follow Sciency Thoughts on Facebook.