Sunday 19 May 2019

Asteroid 2019 JW5 passes the Earth.

Asteroid 2019 JW5 passed by the Earth at a distance of about 898 000 km (2.34 times the average distance between the Earth and the Moon, or 0.60% of the distance between the Earth and the Sun), slightly before 10.10 pm GMT on Monday 13 May 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 JW5 has an estimated equivalent diameter of 6-20 m (i.e. it is estimated that a spherical object with the same volume would be 6-20 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 22 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of 2019 JW5. Minor Planet Center.

2019 JW5 was discovered on 10 May 2019 (three days before its closest approach to the Earth)  by the University of Hawaii's PANSTARRS telescope. The designation 2019 JW5 implies that it was the 142nd asteroid (asteroid W5 - 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 W5 = 22 + (24 X 5) = 142) discovered in the first half of May 2019 (period 2019 J).

2019 JW5 has a 772 day orbital period and an eccentric orbit tilted at an angle of 8.21° to the plane of the Solar System, which takes it from 0.89 AU from the Sun (i.e. 89% of he average distance at which the Earth orbits the Sun) to 2.40 AU from the Sun (i.e. 240% of the average distance at which the Earth orbits the Sun, and considerably outside 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 close encounters between the asteroid and Earth occasionally occur, with the next predicted in September 2021.

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