Asteroid 2019 SG1 passed by the Earth at a distance of about 849 000
km (2.21 times the average distance between the Earth and the Moon, or
0.57% of the distance between the Earth and the Sun), slightly before 9.10 pm
GMT on Sunday 22 September 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 SG1 has an estimated
equivalent
diameter of 6-17 m (i.e. it is estimated that a spherical object
with
the same volume would be 6-17 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 25 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2019 SG1. JPL Small Body Database.
2019 SG1 was discovered on 20 September 2019 (two days before its closest encounter with 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 2019 SG1
implies that the asteroid was the 31st object (asteroid G1 -
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 G1 = 7 + (24 X 1) = 31) discovered in the second half of September 2019 (period 2010 S).
2019 SU2 has a 1398 day orbital period and an eccentric orbit
tilted at an angle of 2.32° to the plane of the Solar System, which
takes it from 0.74 AU from the Sun (i.e. 74% of he average distance at
which the Earth orbits the Sun) to 4.15 AU from the Sun (i.e. 415% of
the
average distance at which the Earth orbits the Sun, and more that 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).
See also...
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