Asteroid 2018 FF3 passed by the Earth at a distance of about 435 200 km (1.13 times the average distance between the Earth and the Moon, or 0.29% of the distance between the Earth and the Sun), slightly before 3.00 am GMT on Friday 23 March 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 FF3 has an estimated equivalent diameter of 9-28 m (i.e. it is estimated that a spherical object with the same volume would be 9-28 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 38 and 18 km above the ground, with only fragmentary material reaching the Earth's surface.
2018 FF3 was discovered on 21 March 2018 (two days before its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2018 FF3 implies that it was the 81st asteroid (asteroid F3) discovered in the second half of March 2018 (period 2018 F).
2018 FF3 has a 613 day orbital period and an eccentric orbit tilted at an angle of 16.6° to the plane of the Solar System, which takes it from 0.92 AU from the Sun (i.e. 92% of he average distance at which the Earth orbits the Sun) to 1.90 AU from the Sun (i.e. 190% of the average distance at which the Earth orbits the Sun, and outside the orbit of the 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 2018 FF3 has occasional close encounters with the planet Earth, with the last thought to have occurred in August 2013, and the next predicted for August this year.
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