Asteroid 2018 XG5 passed by the Earth at a distance of about 9 980 000
km (6.18 times the average distance between the Earth and the Moon, or 6.67% of the distance between the Earth and the Sun), slightly after
8.10 am
GMT on Friday 10 May 2019. There was no danger of
the asteroid hitting us, though were it to do so it would have
presented a significant threat. 2018 XG5 has an estimated
equivalent
diameter of 180-570 m (i.e. it is estimated that a spherical object
with
the same volume would be 180-570 m in diameter), and an object of this
size would be predicted to be capable of
passing through the Earth's
atmosphere relatively intact, impacting the ground directly with an
explosion that would be between about 12 000 and 350 000 times as powerful
as the
Hiroshima
bomb. Such an impact would result in an impact crater between 3 and 8 km
in
diameter
and devastation on a global scale, as well as climatic effects that
would last decades or even centuries.
The calculated orbit of 2018 XG5. JPL Small Body Database.
2018 XG5 was discovered on 13 December 2018 by the University of Hawaii's PANSTARRS telescope. The
designation 2018 XG5 implies that it was the 127th asteroid (asteroid G5 -
in numbering asteroids the letters A-Y, excluding I, are assigned
numbers from 1 to 24, with a number added to the end each time the
alphabet is ended, so that A = 1, A1 = 25, A2 = 49, etc., which means that G5 = 7 + (24 X 5) = 127)
discovered in the first half of December 2018 (period 2018 X).
2018 XG5 has a 1388 day orbital period and an eccentric orbit
tilted at an angle of 12.9° to the plane of the Solar System, which
takes it from 0.92 AU from the Sun (i.e. 82% of he average distance at
which the Earth orbits the Sun) to 3.95 AU from the Sun (i.e. 395% of
the
average distance at which the Earth orbits the Sun, which is considerably 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 close
encounters between the asteroid and Earth are extremely common, with the
last having occurred in April 2000 and the next predicted
in April 2028. As an asteroid probably larger than 150 m in diameter
that occasionally comes within 0.05 AU of the Earth, 2018 XG5 is also
classified as a Potentially Hazardous Asteroid. 2018 XG5 also has
occasional close encounters with the planet Jupiter, with the last having
occurred in September 1998, and the next predicted for May 2070.
See also...
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