Asteroid 2018 XP2 passed by the Earth at a distance of about 388 000
km (1.01 times the average distance between the Earth and the Moon, or
0.02% of the distance between the Earth and the Sun), at about 9.50 pm
GMT on Saturday 8 December 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 XP2 has an estimated
equivalent
diameter of 4-14 m (i.e. it is estimated that a spherical object
with
the same volume would be 4-14 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 28 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2018 XP2. Minor Planet Center.
2018 XP2 was discovered on 10 December 2018 (two days after 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 XP2 implies that the asteroid was the 65th object (object P2) discovered
in the first half of December 2018 (period 2018 X).
2018 XP2
has an 890 day orbital period and an eccentric orbit
tilted at an angle of 66.3° to the plane of the Solar System, which
takes it from 0.43 AU from the Sun (i.e. 43% of he average distance at
which the Earth orbits the Sun and slightly outside the orbit of the planet Mercury) to 3.19 AU from the Sun (i.e. 3.19% of
the
average distance at which the Earth orbits the Sun, ,ore than twice 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). As such the asteroid has
occasional close encounters with the planet Earth, which it is expected to pass again in May 2072. The
asteroid also has occasional close encounters with the planet Mars,
which it last came close to in February 2016 and is next predicted to pass
in August 2077.
See also...
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