Asteroid 2018 XB passed by the Earth at a distance of about 793 000
km (2.06 times the average distance between the Earth and the Moon, or
0.53% of the distance between the Earth and the Sun), before 2.20 pm
GMT on Sunday 2 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 XB has an estimated
equivalent
diameter of 3-12 m (i.e. it is estimated that a spherical object
with
the same volume would be 3-12 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 30 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2018 XB. Minor Planet Center.
2018 XB was discovered on 1 December 2018 (the day before its closest approach to the Earth) by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2018 XB
implies that the asteroid was the second object (object B) discovered in the first half of December 2018 (period 2018 X).
2018 XB
has an 565 day orbital period and an eccentric orbit
tilted at an angle of 4.06° to the plane of the Solar System, which
takes it from 0.93 AU from the Sun (i.e. 93% of he average distance at
which the Earth orbits the Sun) to 1.73 AU from the Sun (i.e. 173% of
the
average distance at which the Earth orbits the Sun, further from the Sun than 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 September 2021.
See also...
Follow Sciency Thoughts on Facebook.