Monday 11 September 2017

Asteroid 2017 QB35 passes the Earth.

Asteroid 2017 QB35 passed by the Earth at a distance of about 356 800 km (0.93 times the average distance between the Earth and the Moon, or 0.24% of the distance between the Earth and the Sun), slightly after 1.40 am GMT on Sunday 3 September 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 QB35 has an estimated equivalent diameter of 2-8 m (i.e. it is estimated that a spherical object with the same volume would be 2-8 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 more than 35 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2017 QB35 Minor Planet Center.
2017 QB35 was discovered on 31 August 2017 (three days before 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 QB35 implies that the asteroid was the 877th object (object B35) discovered in the second half of August 2017 (period 2017 Q). 

2017 QB35 has a 327 day orbital period, with an elliptical orbit tilted at an angle of 5.33° to the plain of the Solar System which takes in to 0.80 AU from the Sun (480% of the distance at which the Earth orbits the Sun) and out to 1.06 AU (6% further away from the Sun than the Earth). This means that close encounters between the asteroid and Earth are fairly common, with the last thought to have happened in March this year and the next predicted in June 2025. It also has close encounters with the planet Venus, with the next expected in January 2027. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2017 QB35 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid.
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