Asteroid 2018 WZ1 passed by the Earth at a distance of about 109 100
km (0.27 times the average distance between the Earth and the Moon, or
0.07% of the distance between the Earth and the Sun), before 10.30 am
GMT on Tuesday 27 November 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 WZ1 has an estimated
equivalent
diameter of 2-7 m (i.e. it is estimated that a spherical object
with
the same volume would be 2-7 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 more than 36 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2018 WZ1. Minor Planet Center.
2018 WZ1 was discovered on 28 November 2018 (the day 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 WZ1implies that the asteroid was the 50th object (object Z1) discovered in the second half of November 2018 (period 2018 W).
2018 WZ1
has an 820 day orbital period and an eccentric orbit
tilted at an angle of 6.01° to the plane of the Solar System, which
takes it from 0.80 AU from the Sun (i.e. 80% of he average distance at
which the Earth orbits the Sun) to 2.63 AU from the Sun (i.e. 263% of
the
average distance at which the Earth orbits the Sun, much further 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 last came
close to in July 2016, and is expected to pass again in December 2092. The
asteroid also has occasional close encounters with the planet Venus,
which it is expected to next pass in January 2095 and Mars which it is next predicted to pass
in November 2090.
See also...
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