Asteroid 2019 XN passed by the Earth at a distance of about 931 000
km (2.43 times the average distance between the Earth and the Moon, or
0.62% of the distance between the Earth and the Sun), at about 11.45 am
GMT on Friday 6 December 2019. There was no danger of
the asteroid hitting us, though were it to do so it would not have
presented a significant threat. 2019 XN has an estimated
equivalent
diameter of 5-17 m (i.e. it is estimated that a spherical object
with
the same volume would be 5-17 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 2019 XN. JPL Small Body Database.
2019 XN was discovered on 3 December 2019 (four days before its closest encounter with 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 2019 XN implies that the asteroid was the thirteenth object (asteroid N - 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 N = 13) discovered in the first half of December 2019 (period 2019 X).
2019 XN has a 1458 day orbital period and an eccentric orbit
tilted at an angle of 0.39° to the plane of the Solar System, which
takes it from 0.95 AU from the Sun (i.e. 95% of he average distance at
which the Earth orbits the Sun) to 4.08 AU from the Sun (i.e. 408% of
the
average distance at which the Earth orbits the Sun, more than twice as distant from the Sun as 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). This means that 2019 XN
occasionally comes close to the Earth, with the such encounter having happened in January 2008 and the next predicted for October 2023. 2019 XN also has occasional close encounters with the planet Mars, with the last having occurred in November 2003.
See also...
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