Asteroid
2016 HD3 passed by the Earth at a distance of 843 000 km (2.19 times
the average distance between the Earth and the Moon, or 0.56% of
the average distance between the Earth and the Sun), slightly before 6.10 am GMT on Mondya 2 May 2016. There was no
danger
of the asteroid
hitting us, though had it done so it would have presented no
threat. 2016 HD3 has an estimated equivalent diameter of 4-15 m (i.e.
it is estimated that a spherical object with the same volume would be 4-15 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 42 and 26 km above the ground, with only fragmentary
material reaching the Earth's surface.
The calculated orbit of 2016 HD3. JPL Small Body Database.
2016 HD3 was discovered on 27 April 2016 (five 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
2016 HD3 implies that the asteroid was the 79th object (object D3)
discovered in the second half of April 2016 (period 2016 H).
2016 HD3 has a 322 day orbital period, with an elliptical orbit tilted at
an angle of 0.63° to the plain of the Solar System which takes in to
0.70 AU from the Sun (70% of the distance at which the Earth orbits the
Sun and approximately the orbit of the planet Venus) and out to
1.14 AU (14%
further away from the Sun than the Earth). This means that close
encounters between the asteroid and Earth are fairly common, with the
last thought to have happened in September 2015 and the next predicted in November 2022. 2016 HD3 also has frequent close encounters with the
planet Venus, with the last thought to have occurred in April 2011
and
the next predicted for July 2023. Although it does cross the Earth's
orbit and is briefly
further from the Sun on each cycle, 2016 HD3 spends most of its time
closer to the Sun than we are, and is therefore classified as an Aten
Group Asteroid.
See also...
Asteroid 2016 GD241 passes the Earth. Asteroid
2016 GD241 passed by the Earth at a distance of 7 643 000 km
(19.9 times the average distance between the Earth and the Moon, or
5.12% of the average distance between the Earth and the Sun), slightly
before 4.30 am GMT on Moday 2 May...
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