Asteroid
2016 XE passed by the Earth at a distance of 566 800 km (1.47 times
the
average distance between the Earth and the Moon, 0.38% of the average
distance
between the Earth and the Sun), slightly after 8.40 am GMT on Wednesday 7
December 2016. There was no danger of the asteroid hitting us, though
had it
done so it would have presented no threat. 2016 XE 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 2016 XE. Minor Planet Center.
2016 XE was discovered on 1 December 2016 (six 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 2016 XE
implies that the asteroid was the fifth object (object XE) discovered in the first half of December 2016 (period 2016 X).
2016 XE is calculated to have a 398 day orbital
period and an elliptical orbit tilted at an angle of 0.97° to the plain of the
Solar System that takes it from 0.80 AU from the Sun (i.e. 80% of the average
distance at which the Earth orbits the Sun) to 1.31 AU from the Sun (i.e. 131%
of the average distance at which the Earth 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 close encounters between the
asteroid and Earth are extremely common, with the last having occurred
in November 2015 and the next predicted in September 2017. 2016 XE also has frequent close encounters with the
planet Mars, with the last calculated to have happened in June 1975 next predicted for September 2018.
See also...
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