Asteroid 2015 NA14 passed by the Earth at a distance of 9 099 000 km (23.7 times the average distance between the Earth and the Moon, or 6.08% of the average distance between the Earth and the Sun), at about 6.05 pm GMT on Friday 31 July 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented a considerable threat. 2015 NA14 has an estimated equivalent diameter of 71-230 m (i.e. a spherical body with the same mass would be 71-230 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 400 megatons (about 23 500 times the explosive energy of the Hiroshima bomb), causing devastation over a wide area and creating a crater over 3.5 kilometers across, and resulting in global climatic problems that could last for decades or even centuries.
The calculated orbit of 2015 NA14. JPL Small Body Database.
2015 NA14 was discovered on 15 July 2015 (sixteen days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2015 NA14 implies that it was the 351st asteroid (asteroid A14) discovered in the first half of July 2015 (period 2015 N).
2015 NA14 has a 347 day orbital period, with an elliptical orbit tilted at an angle of 6.37° to the plain of the Solar System which takes in to 0.79 AU from the Sun (79% of the distance at which the Earth orbits the Sun, slightly outside the orbit of 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 November 2014 and the next predicted in July 2016. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2015 NA14 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid. This also means that close encounters between 2015 NA14 and Venus are quite common, with the last having occurred in December 2013 and the next predicted for June 2024.
See also...
Asteroid 2015 OQ21 passed by the Earth at a distance of 567 900 km (1.48 times the average distance between the Earth and the Moon, or 0.38% of the average distance between the Earth and the Sun), at about midnight GMT between Thursday 23 and...
Asteroid (242191) 2003 NZ6 passed by the Earth at a distance of 12 470 000 km (32.4 times the average distance between the Earth and the Moon, or 8.33% of the average distance between the Earth and the...
Asteroid (385186) 1994 AW1 passed by the Earth at a distance of 9 725 000 km (25.3 times the average distance between the Earth and the Moon, or 6.50% of the average distance between the Earth and the...
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