Sunday 3 September 2017

Asteroid 2017 RC passes the Earth.

Asteroid 2017 RC passed by the Earth at a distance of about 928 000 km (2.41 times the average distance between the Earth and the Moon, or 0.62% of the distance between the Earth and the Sun), at about 5.20 pm GMT on Monday 28 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 RC 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 36 and 28 km above the ground, with only fragmentary material reaching the Earth's surface.

The calculated orbit of 2017 RC Minor Planet Center.

2017 RC was discovered on 1 September 2017 (four days 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 RC implies that the asteroid was the third object (object C) discovered in the first half of September 2017 (period 2017 C). 

2017 RC has a 702 day orbital period and an eccentric orbit tilted at an angle of 3.13° to the plane of the Solar System, which takes it from 0.90 AU from the Sun (i.e. 90% of he average distance at which the Earth orbits the Sun) to 2.20 AU from the Sun (i.e. 220% of the average distance at which the Earth orbits the Sun, more than the distance at which the planet Mars orbits). This means that the asteroid has occasional close encounters with the Earth, with the next predicted in May 2019. 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).
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