Asteroid 2015 BD511 passed by the Earth at a distance of 1 714 000 km (4.47 times the average distance between the Earth and the Moon, or 1.1 % of the average distance between the Earth and the Sun), slightly before 0.50 am GMT on Friday 30 January 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 BD511 has an estimated equivalent diameter of 7-25 m (i.e. it is estimated that a spherical object with the same volume would be 7-25 m in diameter), and an object of this size would be expected to break up in the atmosphere between 36 and 20 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2015 BD511. JPL Small Body Database.
2015 BD511 was discovered on 26 January 2015 (four days before its closest approach to the Earth) by the University of Hawaii's PANSTARRS telescope on Mount Haleakala on Maui. The designation 2015 BD511 implies that it was the 12 779th asteroid (asteroid D511) discovered in the second half of January 2015 (period 2015 B).
2015 BD511 has a 640 day year orbital period and an eccentric orbit tilted at an angle of 12.1° to the plane of the Solar System, which takes it from 0.59 AU from the Sun (i.e. 59% of the average distance at which the Earth orbits the Sun, inside the orbit of Venus) to 2.31 AU from the Sun (i.e. 231% of the average distance at which the Earth orbits the Sun, considerably outside the orbit of Mars). 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 the asteroid and Earth are fairly common, with the last having occured in August 2013. Close encounters between 2015 BD511 and Venus are also fairly common, with the last having occurred in December 1951.
See also...
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