Asteroid 2017 YQ6 passed by the Earth at a distance of about 724 700 km (1.88 times the average distance between the Earth and the Moon, or 0.48% of the distance between the Earth and the Sun), slightly after 2.20 am GMT on Wednesday 27 December 2017. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2017 YQ6 has an estimated equivalent diameter of 4-15 m (i.e. it is estimated that a spherical object with the same volume would be 4-15 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 26 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2017 YQ6. Minor Planet Center.
2017 YQ6 was discovered on 26 December 2017 (the day after its closest approach to 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 2017 YQ6 implies that the asteroid was the 166th object (object Q6) discovered in the second half of December 2017 (period 2017 Y).
2017 YQ6 has a 921 day orbital period and an eccentric orbit tilted at an angle of 6.19° to the plane of the Solar System, which takes it from 0.86 AU from the Sun (i.e. 86% of he average distance at which the Earth orbits the Sun) to 2.85 AU from the Sun (i.e. 285% of the average distance at which the Earth orbits the Sun, and considerably more distant from the Sun than 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). This means that the asteroid has occasional close encounters with the Earth, with the next predicted in January 2079.
Follow Sciency Thoughts on Facebook.