Asteroid
2017 AP4 passed by the Earth at a distance of 859 900 km (2.24 times
the
average distance between the Earth and the Moon, 0.57% of the average
distance
between the Earth and the Sun), slightly before 1.200 am GMT on Sunday 1 January 2017. There was no danger of the asteroid hitting us, though
had it
done so it would have presented no threat. 2017 AP4 has an estimated
equivalent diameter of 7-25 m (i.e. it is estimated that a spherical
object
with the same volume would be 7-25 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 37 and 20 km above the ground, with only
fragmentary
material reaching the Earth's surface.
The calculated orbit of 2017 AP4. Minor Planet Center.
2017 AP4 was discovered on 4 January 2017 (three days after its closest approach to the Earth) by the University of Hawaii's PANSTARRS
telescope on Mount Haleakala on Maui. The designation 2017 AP4 implies
that it was the 115th asteroid (asteroid P4) discovered in the first
half of January 2017 (2017 A).
2017 AP4 has a 1096 day orbital period and an eccentric orbit
tilted at an angle of 1.45° to the plane of the Solar System, which
takes it from 0.97 AU from the Sun (i.e. 97% of the average distance at
which the Earth orbits the Sun) to 3.19 AU from the Sun (i.e. 319% of the
average distance at which the Earth orbits the Sun, and more than twice the distance at which the planet Mars orbits). 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).
See also...
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