Tuesday 24 October 2017

Asteroid 2017 TE5 passes the Earth.

Asteroid 2017 TE5 passed by the Earth at a distance of about 513 850 km (1.34 times the average distance between the Earth and the Moon, or 0.34% of the distance between the Earth and the Sun), slightly before 11.10 am GMT on Tuesday 17 October 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 TE5 has an estimated equivalent diameter of 12-38 m (i.e. it is estimated that a spherical object with the same volume would be 12-38 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 30 and 12 km above the ground, with only fragmentary material reaching the Earth's surface.

 Image of 2017 TE50 taken on 17 October 2017 from Ceccano in Italy with the Elena Telescope. The asteroid is the point in the centre of the picture. The longer lines are stars, their elongation being caused by the telescope tracking the asteroid over the length of the exposure, in this case three 90 second exposures, giving each star a triple line. Gianluca Masi/Virtual Telescope.

2017 TE5 was discovered on 14 October 2017 (three 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 2017 TE5 implies that it was the 130th asteroid (asteroid E5) discovered in the first half of October 2017 (period 2017 T).
The calculated orbit of 2017 TE5. Minor Planet Center.

2017 TE5 has an 899 day orbital period and an eccentric orbit tilted at an angle of 10.3° 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 2.73 AU from the Sun (i.e. 273% of the average distance at which the Earth orbits the Sun, considerably more than the distance at which the planet Mars orbits the Sun). 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 last thought to have happened in January 2013.

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