Asteroid
2015 XX169 passed by the Earth at a distance of 3 231 000 km (8.41
times the average distance between the Earth and the Moon, or 2.16% of
the average distance between the Earth and the Sun),
slightly after 3.00 pm GMT on Monday 14 December 2015. There was no
danger
of the asteroid
hitting us, though had it done so it would have presented only a minor
threat. 2015 XX169 has an estimated equivalent diameter of 6-20 m (i.e.
it is estimated that a spherical object with the same volume would be
6-20 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 38 and 22 km above the ground, with only fragmentary
material reaching the Earth's surface.
The calculated orbit of 2015 XX169. JPL Small Body Database.
2015 XX169 was discovered on 9 December 2015 (three 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
2015 XX169 implies that the asteroid was the 4248th object (object X169)
discovered in the first half of December 2015 (period 2015 X).
2015 XX169 has a 364 day orbital period, with an elliptical orbit tilted at
an angle of 3.10° to the plain of the Solar System which takes in to
0.82 AU from the Sun (82% of the distance at which the Earth orbits the
Sun) and out to 1.18 AU (18%
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 December 2014 and the next predicted in December 2016 . Although it does cross the Earth's orbit and is briefly
further from the Sun on each cycle, 2015 XX169 spends most of its time
closer to the Sun than we are, and is therefore classified as an Aten
Group Asteroid.
See also...
Asteroid 2015 XA169 passes the Earth. Asteroid
2015 XA169 passed by the Earth at a distance of 2 848 000 km (7.41
times the average distance between the Earth and the Moon, or 1.90% of
the average distance between the Earth and the Sun),
slightly before 3.00 pm GMT on Saturday 12...
Asteroid 2015 XV261 passes the Earth. Asteroid
2015 XV261 passed by the Earth at a distance of 2 609 000 km (6.78
times the average distance between the Earth and the Moon, or 1.75% of
the average distance between the Earth and the Sun),
slightly after 3.05 am GMT on Tuesday 8 December...
Asteroid 2015 SV2 passes the Earth. Asteroid 2015 SV2 passed by the Earth at a distance of 14 800 000 km (38.5 times
the average distance between the Earth and the Moon, or 9.89% of the
average distance between the Earth and the Sun), at about 3.45 pm
GMT on Saturday 5 December...
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