Monday 14 October 2019

Asteroid 2019 TJ5 passes the Earth.

Asteroid 2019 TJ5 passed by the Earth at a distance of about 381 200 km (2.48 times the average  distance between the Earth and the Moon, or 0.64% of the distance between the Earth and the Sun), slightly before 1.00 am GMT on Tuesday 8 October 2019. There was no danger of the asteroid hitting us, though were it to do so it would not have presented a significant threat. 2019 TJ5 has an estimated equivalent diameter of 9-27 m (i.e. it is estimated that a spherical object with the same volume would be 9-27 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 33 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of 2019 TJ5. JPL Small Body Database.

2019 TJ5 was discovered on 9 October 2019 (the day after 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 2019 TJ5 implies that it was the 129th asteroid (asteroid J5 - in numbering asteroids the letters A-Y, excluding I, are assigned numbers from 1 to 24, with a number added to the end each time the alphabet is ended, so that A = 1, A1 = 25, A2 = 49, etc., which means that J5 = 9 + (24 X 5) = 129) discovered in the first half of October 2019 (period 2019 T).

2019 TJ5 is calculated to have an 1516 day orbital period and an eccentric orbit tilted at an angle of 2.63° to the plane of the Solar System, which takes it from 0.92 AU from the Sun (i.e. 92% of the average distance at which the Earth orbits the Sun) to 4.24 AU from the Sun (i.e. 424% of the average distance at which the Earth orbits the Sun, more than twice the orbit of 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 2019 TJ5 has occasional close encounter with the Earth, with the most recent previous one having happened in June 2015.

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