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 October 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented a considerable threat. 2015 TC145 has an estimated equivalent diameter of 41-130 m (i.e. a spherical body with the same mass would be 41-130 m in diameter), and an object towards the upper end of this range would pass through the atmosphere and directly impact the ground with a force of about 65 megatons (about 3800 times the explosive energy of the Hiroshima bomb), causing devastation over a wide area and creating a crater about 2 km across, and resulting in global climatic problems that could last for years or even decades.
The calculated orbit of 2009 TC145. JPL Small Body Database.
2015 TC145 was discovered on 10 October 2015 (the day of its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2015 TC145 implies that it was the 3628th asteroid (asteroid C145) discovered in the first half of October 2015 (period 2015 T).
2015 TC145 has an 1335 day orbital period and an eccentric orbit tilted at an angle of 2.56° to the plane of the Solar System that takes it from 1.06 AU from the Sun (i.e. 106 % of the average distance at which the Earth orbits the Sun) to 3.68 AU from the Sun (i.e. 368% of the average distance at which the Earth orbits the Sun, considerably over twice 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).
See also...
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...
Asteroid 2015 TC144 passed by the Earth at a distance of 3 255 000 km (8.47 times the average distance between the Earth and the Moon, or 2.18% of the average distance between the Earth and the Sun), at about 8.35 pm GMT on Thursday 8 October...
Asteroid 2009 TK passed by the Earth at a distance of 6 747 000 km (17.5 times the average distance between the Earth and the Moon, or 4.51% of the average distance between the Earth and the Sun), slightly after 11.50 am GMT on Monday 5 October 2015. There...
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