Asteroid 2018 NH passed by the Earth at a distance of about 433 500
km (1.12 times the average distance between the Earth and the Moon, or
0.29% of the distance between the Earth and the Sun), at about 5.20 pm
GMT on Monday 2 July 2018. There was no danger of
the asteroid hitting us, though were it to do so it would not have
presented a significant threat. 2018 NH has an estimated
equivalent
diameter of 22-68 m (i.e. it is estimated that a spherical object
with
the same volume would be 22-68 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 20 and 4 km above the ground, with only fragmentary material
reaching the Earth's surface.
The calculated orbit of 2018 NH. Minor Planet Center.
2018 NH was discovered on 4 July 2018 (two days 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 2018 NH
implies that the asteroid was the eighth object (object H) discovered in the first half of July 2018 (period 2018 N).
2018 NH has an 948 day orbital period and an eccentric orbit
tilted at an angle of 35.6° to the plane of the Solar System, which
takes it from 0.91 AU from the Sun (i.e. 91% of he average distance at
which the Earth orbits the Sun) to 2.87 AU from the Sun (i.e. 287% of
the
average distance at which the Earth orbits the Sun, and almost twice as far 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).
See also...
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