Asteroid 2015 MA passed by the Earth at a distance of 656 700 km (1.71 times the average distance between the Earth and the Moon, or 0.44% of the average distance between the Earth and the Sun), slightly before 2.10 am GMT on Wednesday 17 June 2015. There was no danger of the asteroid hitting us, though had it done so it would have presented only a minor threat. 2015 MA has an estimated equivalent diameter of 9-30 m (i.e. it is estimated that a spherical object with the same volume would be 9-30 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 16 km above the ground, with only fragmentary material reaching the Earth's surface.
The calculated orbit of 2015 MA. JPL Small Body Database.
2015 MA was discovered on 16 June 2015 (the day before its closest approach to the Earth) by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2015 MA implies that it was the first asteroid (asteroid A) discovered in the second half of June 2015 (period 2015 M).
2015 MA has a 436 day orbital period and an eccentric orbit tilted at an angle of 23.5° to the plane of the Solar System, which takes it from 0.71 AU from the Sun (i.e. 19% of the average distance at which the Earth orbits the Sun, and sightly inside the orbit of the planet Venus) to 1.53 AU from the Sun (i.e. 153% of the average distance at which the Earth orbits the Sun, and slightly outside the orbit of the planet 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 extremely common, with the last having occurred in January 2011 and the next predicted in December 2016.
See also...
Asteroid (1566) 1949 MA Icarus passed by the Earth at a distance of 8 054 000 km (20.9 times the average distance between the Earth and the Moon, or 5.38 % of the average distance between the Earth and the...
Asteroid 2015 KQ120 passed by the Earth at a distance of 3 279 000 km (8.53 times the average distance between the Earth and the Moon, or 2.19% of the average distance between the Earth and the Sun), slightly after 8.35 pm GMT on Sunday 31 May...
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