Sciency Thoughts: Asteroid 2006 XD2 passes the Earth.

Asteroid 2006 XD2 passed by the Earth at a distance of about 17 460 000 km (45.42 times the average distance between the Earth and the Moon), slightly after 8.20 pm GMT on Sunday 1 June 2014. There was no danger of the asteroid hitting us, though were it to do so it would have presented a considerable threat. 2006 XD2 has an estimated equivalent diameter of 120-380 m (i.e. it is estimated that a spherical object with the same volume would be 120-380 m in diameter), and an object of this size would be predicted to be capable of passing through the Earth's atmosphere relatively intact, impacting the ground directly with an explosion that would be 3500-165 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater 1-6 km in diameter and devastation on a global scale, as well as climatic effects that would last decades.

Image of 2006 XD2 captured on 20 December 2006. The asteroid is the dot at the center of the picture, the elongate objects are stars; this is caused by the camera tracking the asteroid on a long exposure. Nick James/The Astronomer.

2006 XD2 was discovered on 12 December 2006 by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research Laboratory in Socorro, New Mexico. The designation 2008 WK32 implies that it was the 811th asteroid (asteroid K32) discovered in the second half of November 2008 (period 2008 W).

2006 XD2 has an 522 day year orbital period that takes it from 0.73 AU from the Sun (i.e. 73% of the average distance at which the Earth orbits the Sun) to 1.81 AU from the Sun (i.e. 181% of the average distance at which the Earth orbits the Sun, considerably more than the distance at which the planet Mars orbits the Sun). 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). As an asteroid on an Earth-orbit crossing trajectory which is large enough to cause serious harm should it collide with Earth it is also classified as a Potentially Hazardous Asteroid.