Asteroid 2017 QF3 passed by the Earth at a distance of about 553 100 km (1.44 times the average distance between the Earth and the Moon, or 0.37% of the distance between the Earth and the Sun), slightly before 10.55 pm GMT on Tuesday 23 August 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 QF3 has an estimated equivalent diameter of 4-16 m (i.e. it is estimated that a spherical object with the same volume would be 4-16 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 25 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2017 QF3 Minor Planet Center.
2017 QF3 has a 507 day orbital period and an eccentric orbit tilted at an angle of 2.50° 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, roughly distance at which the planet Venus orbits the Sun) to 1.79 AU from the Sun (i.e. 179% of the average distance at which the Earth orbits the Sun, and 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 close encounters between the asteroid and Earth are extremely common, with the last having occurred in March 2015 and the next predicted in Mach 2029.
2017 QF3 also has frequent close encounters with the planets Venus, which it is thought to have last passed in June 2016, Mars which it last came close to in March 1968. Asteroids which make close passes to multiple planets are considered to be in unstable orbits, and are often eventually knocked out of these orbits by these encounters, either being knocked onto a new, more stable orbit, dropped into the Sun, knocked out of the Solar System or occasionally colliding with a planet.
Follow Sciency Thoughts on Facebook.