Asteroid
2015 WP2 passed by the Earth at a distance of 229 800 km (0.6
times the average distance between the Earth and the Moon, or 0.16% of
the average distance between the Earth and the Sun; but 575.4 times as far from the Earth as the International Space Station and 11.4 times as distant as the satellites that transmit GPS signals), slightly before 1.45 am on Friday 20 November 2015. There was no danger of the asteroid
hitting us, though had it done so it would have presented only a minor
threat. 2015 WP2 has an estimated equivalent diameter of 2.6-5.7 m (i.e.
it is estimated that a spherical object with the same volume would be 2.6-5.7 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 40 km above the ground, with only fragmentary
material reaching the Earth's surface.
The calculated orbit of 2015 WP2. JPL Small Body Database.
2015 WP2 was discovered on 21 November 2015 (the day after 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
2015 WP2 implies that the asteroid was the 65h object (object P2)
discovered in the first second half of November 2015 (period 2015 W).
2015 WP2 has a 605 day orbital period and an eccentric orbit tilted at an
angle of 1.58° to the plane of the Solar System that takes it from 0.77
AU from the Sun (i.e. 77% of the average distance at which the Earth
orbits the Sun, and slightly outside the orbit of Venus) to 2.03 AU from the Sun (i.e. 203% of the average
distance at which the Earth orbits the Sun, considerably more than the
distance at which Mars orbits the Sun). 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). 2015 WP2 also has occasional
close encounters with the planet Mars, with the next predicted in April 2021.
See also...
Asteroid 2015 VV2 passes the Earth. Asteroid
2015 VV2 passed by the Earth at a distance of 6 623 000 km (17.2
times the average distance between the Earth and the Moon, or 4.43% of
the average distance between the Earth and the Sun), slightly after
10.30
pm on Wednesday 18 November 2015...
Asteroid 2015 VD105 passes the Earth. Asteroid
2015 VD105 passed by the Earth at a distance of 2 777 000 km (7.22
times the average distance between the Earth and the Moon, or 1.86% of
the average distance between the Earth and the Sun), slightly before 4.25
pm on Monday 16 November...
Asteroid 2015 VU65 passes the Earth. Asteroid
2015 VU65 passed by the Earth at a distance of 2 009 000 km (5.23
times the average distance between the Earth and the Moon, or 1.34% of
the average distance between the Earth and the Sun), slightly before
10.05
pm on Saturday 14...
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