Thursday 10 October 2019

Asteroid 2019 SP3 passes the Earth.

Asteroid 2019 SP3 passed by the Earth at a distance of about 371 900 km (0.97 times the average  distance between the Earth and the Moon, or 0.25% of the distance between the Earth and the Sun), slightly after 6.30 am GMT on Thursday 3 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 SP3 has an estimated equivalent diameter of 10-33 m (i.e. it is estimated that a spherical object with the same volume would be 10-33 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 32 and 10 km above the ground, with only fragmentary material reaching the Earth's surface.

 The calculated orbit of 2019 SP3. JPL Small Body Database.

2019 SP3 was discovered on 22 September 2019 (eleven days before its closest approach to the Earth)  by the University of Hawaii's PANSTARRS telescope. The designation 2019 SP3 implies that it was the 87th asteroid (asteroid U3 - 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 P3 = 15 + (24 X 3) = 87) discovered in the second half of September 2019 (period 2019 S).

2019 SP3 has a 1416 day orbital period and an eccentric orbit tilted at an angle of 1.52° to the plane of the Solar System, which takes it from 0.98 AU from the Sun (i.e. 98% of he average distance at which the Earth orbits the Sun) to 3.95 AU from the Sun (i.e. 395% of the average distance at which the Earth orbits the Sun, and more than twice as far from the Sun as 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).  

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