Asteroid 2014 MV18 passed by the Earth at a distance of about 2 758 000 km (7.17 times the average distance between the Earth and the Moon), slightly before 4.00 pm GMT on Monday 30 June 2014. There was no danger of the asteroid hitting us, though were it to do so it would have presented a real threat. 2014 MV18 has an estimated equivalent diameter of 38-120 m (i.e. it is estimated that a spherical object with the same volume would be 38-120 m in diameter), and an object towards the upper end of this range would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground with an energy equivalent to about 155 megatons of TNT (roughly 9000 times the energy of the Hiroshima bomb). Such an event would result in a crater about 1.5 km across, cause devastation over a wide area around the impact site and would have the potential to affect the climate globally for several years.
The calculated orbit of 2014 MV18. JPL Small Body Database Browser.
2014 MV18 was discovered on 26 June 2014 (four days 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 2014 MV18 implies that it was the 471st asteroid (asteroid V18) discovered in the second half of June 2014 (period 2014 M).
2014 MV18 has a 261 day orbital period, with an elliptical orbit tilted at an angle to the plain of the Solar System which takes in to 0.57 AU from the Sun (57% of the distance at which the Earth orbits the Sun, considerably inside the orbit of the planet Venus) and out to 1.03 AU (3% 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 January 2012 and the next predicted in January 2017. Although it does cross the Earth's orbit and is briefly further from the Sun on each cycle, 2014 MV18 spends most of its time closer to the Sun than we are, and is therefore classified as an Aten Group Asteroid.
See also...
Asteroid 2013 XM24 passed by the Earth at a distance of about 16 920 000 km (44.01 times the average distance between the Earth and...
Asteroid 1994 CJ1 passed by the Earth at a distance of about 13 570 000 km (35.29 times the average distance between the Earth and the...
Asteroid 2014 MG6 passed by the Earth at a distance of 3 647 000 km (9.49 times the average distance between the Earth and the...
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