Asteroid 2017 WG28 passed by the Earth at a distance of about 644 500
km (1.68 times the average distance between the Earth and the Moon, or
0.43% of the distance between the Earth and the Sun), at about 10.00 pm
GMT on Friday 24 November 2017. There was no danger of
the asteroid hitting us, though were it to do so it would not have
presented a significant threat. 2017 WG28 has an estimated
equivalent
diameter of 5-18 m (i.e. it is estimated that a spherical object
with
the same volume would be 5-18 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 40 and 25 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2017 WG28. Minor Planet Center.
2017 WG28 was discovered on 27 November 2017 (three 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 2017 WG28
implies that the asteroid was the 807th object (object G28) discovered in the second half of November 2017 (period 2017 W).
2017 WG28 has a 1458 day orbital period and an eccentric orbit
tilted at an angle of 0.75° to the plane of the Solar System, which
takes it from 0.99 AU from the Sun (i.e. 99% of he average distance at
which the Earth orbits the Sun) to 4.04 AU from the Sun (i.e. 404% of
the
average distance at which the Earth orbits the Sun, more than twice the
distance at which the planet Mars orbits). 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 2017
VC14 has occasional close encounters with the Earth, which it last came
close to in January 2010. The asteroid also has occasional close encounters with the planet Mars, which is last passed in November 2010.
See also...
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