Asteroid 2019 UC passed by the Earth at a distance of about 1 120 000
km (2.92 times the average distance between the Earth and the Moon, or
0.75% of the distance between the Earth and the Sun), slightly before 1.30 am
GMT on Tuesday 29 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 UC has an estimated
equivalent
diameter of 27-87m (i.e. it is estimated that a spherical object
with
the same volume would be 27-87 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 18 and 0.5 km above the ground, with only fragmentary material
reaching the Earth's surface, although, since an object at the upper end of the range would be expected to explode with a force equivalent to 30 megatons of TNT, being directly underneath it would probably be quite unpleasant.
The calculated orbit of 2019 UY7. JPL Small Body Database.
2019 UC was discovered on 18 October 2019 (eleven days after its closest approach to the Earth) by the Atlas MLO Telescope at Mauna Loa Observatory in Hawaii. The designation 2019 UC implies that the asteroid was the third object (object C -
in numbering asteroids the letters A-Z, excluding I, are assigned
numbers from 1 to 25, so that E4 = (24 x 0) + 3 = 3) discovered in the second half of October 2019 (period 2019 U).
2019 UC has a 666 day orbital period and an eccentric orbit
tilted at an angle of 2.82° to the plane of the Solar System, which
takes it from 0.88 AU from the Sun (i.e. 80% of he average distance at
which the Earth orbits the Sun) to 2.10 AU from the Sun (i.e. 210% of
the
average distance at which the Earth orbits the Sun, beyond the orbit of 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 UC occasionally comes close to the Earth, with the
last such encounter having happened in February 2009, and the next
predicted for March 2020. 2019 UC also has occasional close encounters
with the planet Mars, which it last came close to in August 1988 and
is predicted to pass again in April 2031.
See also...
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