Asteroid 2017 MB1 passed by the Earth at a distance of about 8 785 000
km (22.8 times the average distance between the Earth and the Moon, or 5.87% of the distance between the Earth and the Sun), slightly before 8.45
am
GMT on Saturday 22 July 2017. There was no danger of
the asteroid hitting us, though were it to do so it would have
presented a considerable threat. 2017 MB1 has an estimated
equivalent
diameter of 330-1000 m (i.e. it is estimated that a spherical object with
the same volume would be 330-1000 m in diameter), and an object of this
size 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 200 000-2 750 000 times as powerful as the
Hiroshima
bomb. Such an impact would result in an impact crater 5-15 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 2017 MB1. Minor Planet Center.
2017 MB1 was discovered on 19 June 2017 (34 days before its closest approach to 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 2017 MB1
implies that the asteroid was the 27th object (object B1) discovered in the second half of June 2017 (period 2017 M).
2017 MB1 has a 1334 day orbital period and an eccentric orbit
tilted at an angle of 8.51° to the plane of the Solar System, which
takes it from 0.59 AU from the Sun (i.e. 59% of he average distance at
which the Earth orbits the Sun, somewhat less the distance at which the planet
Venus orbits the Sun) to 4.16 AU from the Sun (i.e. 416% of the
average distance at which the Earth orbits the Sun, and almost three times 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 close
encounters between the asteroid and Earth are extremely common, with the
last having occurred in July 2016 and the next predicted
in February 2025. As an asteroid probably larger than 150 m in diameter
that occasionally comes within 0.05 AU of the Earth, 2017 MB1 is also
classified as a Potentially Hazardous Asteroid.
2017 MB1 also
has frequent close encounters with the planets Venus, which it is
thought to have last passed in August 1951, and is next predicted to
pass in January 2025, Mars which it last came close to in August 1955 and
is next predicted to pass in April 2025), and Jupiter, which it last came close to in December 1993, and is next predicted to approach in July 2041. 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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