Asteroid 2017 DB passed by the Earth at a distance of 700 400 km (1.82
times the average distance between the Earth and the Moon, 0.47% of
the average distance between the Earth and the Sun), slightly before 4.35 pm GMT
on Monday 20 February 2017. There was no danger of the asteroid
hitting us, though had it done so it would have presented no threat.
2017 DB has an estimated equivalent diameter of 7-24 m (i.e. it is
estimated that a spherical object with the same volume would be 7-24 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 DB. Minor Planet Center.
2017 DB was discovered on 16 February 2017 (four 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 DB
implies that the asteroid was the second object (object B) discovered in the second half of February 2017 (period 2017 D).
2017 DB has a 453 day orbital period and an eccentric orbit
tilted at an angle of 7.01° to the plane of the Solar System, which
takes it from 0.86 AU from the Sun (i.e. 86% of he average distance at
which the Earth orbits the Sun) to 1.44 AU from the Sun (i.e. 1.44% of
the
average distance at which the Earth orbits the Sun, slightly inside the orbit of 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 common, with the
last having occurred in August 2012 and the next predicted
in September this year.
See also...
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