Asteroid 2008 TC4 passed by the Earth at a distance of about 12 911 000
km (33.6 times the average distance between the Earth and the Moon, or 8.63% of the distance between the Earth and the Sun), slightly before 1.45 am
GMT on Tuesday 24 October 2017. There was no danger of
the asteroid hitting us, though were it to do so it would have
presented a significant threat. 2008 TC4 has an estimated
equivalent
diameter of 94-300 m (i.e. it is estimated that a spherical object
with
the same volume would be 94-300 m in diameter), and an object at the
upper end of this
size range 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 65 000 times as powerful as the
Hiroshima
bomb. Such an impact would result in an impact crater over 4.6 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 2008 TC4. Minor Planet Center.
2008 TC4 was discovered on 7 October 2007 by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research Laboratory in Socorro, New Mexico. The designation 2008 TC4 implies that it was the 103rd asteroid
(asteroid C4) discovered in the first half of October 2008 (period
2008 T).
2008 TC4 has a 252 day orbital period, with an elliptical orbit tilted at
an angle of 10.6° to the plain of the Solar System which takes in to
0.35 AU from the Sun (35% of the distance at which the Earth orbits the
Sun; inside the orbit of the planet Mercury) and out to
1.21 AU (21%
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 October 2015 and the next predicted
in October 2019. Although it does cross the Earth's
orbit and is briefly
further from the Sun on each cycle, 2008 TC4 spends most of its time
closer to the Sun than we are, and is therefore classified as an Aten
Group Asteroid. As an asteroid probably larger than 150 m in diameter
that occasionally comes within 0.05 AU of the Earth, 2008 TC4 is also
classified as a Potentially Hazardous Asteroid.
2008 TC4 also
has frequent close encounters with the planets Mercury, which it is
thought to have last passed in April this year, and is next predicted to
pass in February 2022, and Venus, which it last came close to in February 2004
and
is next predicted to pass in April 2021. Asteroids
which make close passes to multiple planets are considered to be in
unstable orbits, and are often eventually knocked out of these orbits by
these encounters, either being knocked onto a new, more stable orbit,
dropped into the Sun, knocked out of the Solar System or occasionally
colliding with a planet.
See also...
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