Asteroid 2015 TC179 passed by the Earth at a distance of 4 733 000 km (12.3 times the average distance between the Earth and the Moon, or 3.16% of the average distance between the Earth and the Sun), slightly after 8.15 pm on Wednesday 14 October 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 TC179 has an estimated equivalent diameter of 11-36 m (i.e. it is estimated that a spherical object with the same volume would be 11-36 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 30 and 10 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2015 TC179. JPL Small Body Database.
2015 TC179 was discovered on 13 October 2015 (the day before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2015 TC179 implies that it was the 4478th asteroid (asteroid C179) discovered in the first half of October 2015 (period 2015 T).
2015 TC179 has a 661 day orbital period and an eccentric orbit tilted at an angle of 1.09° to the plane of the Solar System that takes it from 1.03 AU from the Sun (i.e. 103 % of the average distance at which the Earth orbits the Sun) to 1.95 AU from the Sun (i.e. 195% of the average distance at which the Earth orbits the Sun, somewhat over the distance at which the planet Mars orbits). It is therefore classed as an Amor Group Asteroid (an asteroid which comes close to the Earth, but which is always outside the Earth's orbit). This means that close encounters between the asteroid and Earth are fairly common, with the most recent having occurred in September 2006 and the next predicted in November 2024. 2015 TC179 is also thought to have occasional close encounters with the planet Mars, with the most recent being calculated to have occurred in April 1978.
See also...
Asteroid 2015 TB25 passed by the Earth at a distance of 3 658 000 km (9.51 times the average distance between the Earth and the Moon, or 2.45% of the average distance between the Earth and the Sun), slightly before 7.55 pm GMT on Sunday 11 October...
Asteroid 2015 TC145 passed by the Earth at a distance of 16 710 000 km (43.4 times the average distance between the Earth and the Moon, or 11.2% of the average distance between the Earth and the Sun), slightly before 3.30 pm GMT on Saturday 10...
Asteroid 2015 TJ238 passed by the Earth at a distance of 17 910 000 km (46.6 times the average distance between the Earth and the Moon, or 12.0% of the average distance between the Earth and the Sun), slightly before 11.10 pm GMT on Friday 9 October...
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