Asteroid 2015 TG144 passed by the Earth at a distance of 5 109 000 km (13.3 times the average distance between the Earth and the Moon, or 3.42% of the average distance between the Earth and the Sun), slightly before 9.00 am on Friday 16 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 TG144 has an estimated equivalent diameter of 14-45 m (i.e. it is estimated that a spherical object with the same volume would be 14-45 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 28 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 TG144 was discovered on 10 October 2015 (six days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2015 TG144 implies that it was the 3607th asteroid (asteroid G144) discovered in the first half of October 2015 (period 2015 T).
2015 TG144 has a 468 day orbital period and an eccentric orbit tilted at an angle of 6.11° to the plane of the Solar System that takes it from 0.87 AU from the Sun (i.e. 87% of the average distance at which the Earth orbits the Sun) to 2.18 AU from the Sun (i.e. 1.49% of the average distance at which the Earth orbits the Sun, roughly the same as the distance at which Mars orbits the Sun). 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 2015 TG144 and the Earth are moderately common, with the next predicted for April 2016.
See also...
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...
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...
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