Asteroid 2018 CH2 passed by the Earth at a distance of about 787 000
km (2.05 times the average distance between the Earth and the Moon, or
0.53% of the distance between the Earth and the Sun), at about 5.50 pm
GMT on Monday 12 February 2018. There was no danger of
the asteroid hitting us, though were it to do so it would not have
presented a significant threat. 2018 CH2 has an estimated
equivalent
diameter of 4-15 m (i.e. it is estimated that a spherical object
with
the same volume would be 4-15 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 43 and 26 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2018 CH2. Minor Planet Center.
2018 CH2 was discovered on 8 February 2018 (four days before its closest approach to 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 2018 CH2
implies that the asteroid was the 58th object (object H2) discovered in the first half of February 2018 (period 2018 C).
2018 CH2 has a 1095 day orbital period and an eccentric orbit
tilted at an angle of 5.47° to the plane of the Solar System, which
takes it from 0.96 AU from the Sun (i.e. 96% of he average distance at
which the Earth orbits the Sun) to 3.19 AU from the Sun (i.e. 319% of
the
average distance at which the Earth orbits the Sun, and slightly more than twice 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 occurred in January 2015 and the next predicted
in February 2024.
See also...
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