Asteroid 2019 UL passed by the Earth at a distance of about 477 800
km (1.24 times the average distance between the Earth and the Moon, or
0.31% of the distance between the Earth and the Sun), slightly after 4.15 pm
GMT on Wednesday 16 October 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 UL has an estimated
equivalent
diameter of 3-10 m (i.e. it is estimated that a spherical object
with
the same volume would be 3-10 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 32 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2019 UL. JPL Small Body Database.
2019 UL was discovered on 19 October 2019 (three 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 UL
implies that the asteroid was the eleventh object (asteroid L -
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 L = 11) discovered in the second half of October 2019 (period 2010 U).
2019 UL has a 282 day orbital period, with an elliptical orbit tilted at
an angle of 1.92° 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 less than the distance at which Venus orbits the Sun) and out to
1.01 AU (1%
further away from the Sun than the Earth). This means that close
encounters between the asteroid and Earth are fairly common, with the
last thought to have happened in November 2016 and the next predicted
in October 2022. Although it does cross the Earth's
orbit and is briefly
further from the Sun on each cycle, 2019 UL
spends most of its time
closer to the Sun than we are, and is therefore classified as an Aten
Group Asteroid. This also means that the asteroid has occasional close
encounters with the planet Venus, with the last calculated to have
occurred in December 2017, and the next predicted for December next year.
See also...
Follow Sciency Thoughts on Facebook.
