Asteroid 2015 AM45 passed by the Earth at a distance of about 12 394 000
km (40.0 times the average distance between the Earth and the Moon, or 10.3% of the distance between the Earth and the Sun), slightly after 9.40 am
GMT on Sunday 22 July 2018. There was no danger of
the asteroid hitting us, though were it to do so it would have
presented a significant threat. 2015 AM45 has an estimated
equivalent
diameter of 75-240 m (i.e. it is estimated that a spherical object
with
the same volume would be 75-240 m in diameter), and an object at the upper end of this 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 32 000 times as powerful as the
Hiroshima
bomb. Such an impact would result in an impact crater 3.5 km
in
diameter
and devastation on a global scale, as well as climatic effects that
would last years or even decades.
2015 AM45 was discovered on 15 January 2015 by the University of Hawaii's PANSTARRS telescope. The designation 2015 AM45 implies that the asteroid was the 1137th object (object M45) discovered in the first half of January 2015 (period 2015 A).
The calculated orbit of 2015 AM45. Minor Planet Center.
2015 AM45 was discovered on 15 January 2015 by the University of Hawaii's PANSTARRS telescope. The designation 2015 AM45 implies that the asteroid was the 1137th object (object M45) discovered in the first half of January 2015 (period 2015 A).
2015 AM45
has an 706 day orbital period and an eccentric orbit
tilted at an angle of 5.58° to the plane of the Solar System, which
takes it from 0.75 AU from the Sun (i.e. 75% of he average distance at
which the Earth orbits the Sun, slightly outside the orbit of the planet Venus) to 2.35 AU from the Sun (i.e. 235% of
the
average distance at which the Earth orbits the Sun, and further 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 close
encounters between the asteroid and Earth are extremely common, with the
last having occurred in September 2016 and the next predicted
in January 2040. As an asteroid probably larger than 150 m in diameter
that occasionally comes within 0.05 AU of the Earth, 2017 TE5 is also
classified as a Potentially Hazardous Asteroid.
2015 AM45 also
has frequent close encounters with the planets Venus, which it is
thought to have last passed in February 2007, and which it is next predicted to pass in October 2074, and Mars, which it last came close
to in May this year
and
is next predicted to pass in February 2066. 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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