Asteroid 2017 XL2 passed by the Earth at a distance of about 12 379 000
km (32.2 times the average distance between the Earth and the Moon, or
8.28% of the distance between the Earth and the Sun), slightly before 2.50 am
GMT on Tuesday 23 June 2020. There was no danger of
the asteroid hitting us, though were it to do so it would have
presented a considerable threat. 2017 XL2 has an estimated
equivalent
diameter of 100-330 m (i.e. it is estimated that a spherical object with
the same volume would be 100-330 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 200-8825 times as powerful as the
Hiroshima
bomb. Such an impact would result in an impact crater roughly 1-5 km
in
diameter
and devastation on a global scale, as well as climatic effects that
would last years or even decades.
The calculated orbit of 2017 XL2. JPL Small Body Database Browser.
2017 XL2 was discovered on 9 December 2017 by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2017 XL2 implies that the asteroid was the 59th object (object L2 -
in numbering asteroids the letters A-Z, 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 L2 = (24 x 2) + 11 = 59) discovered in the first half of December 2017 (period 2017 X).
2017 XL2 has a 1028 day (2.81 year) orbital period, with an elliptical
orbit tilted at
an angle of 16.9° to the plain of the Solar System which takes in to
0.67 AU from the Sun (67% of the distance at which the Earth orbits the
Sun, and slightly inside the orbit of the planet Venus) and out to 3.32 AU (332% of the distance at which the Earth orbits
the sun and more than twice as far from the Sun than the planet Mars).
This means that close
encounters between the asteroid and Earth are fairly common, with the
last having happened in December 2017 and the next predicted
in September 2034. 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 an asteroid probably larger than 150 m in diameter
that occasionally comes within 0.05 AU of the Earth, 2017 XL2
is also
classified as a Potentially Hazardous Asteroid.
See also...
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