Asteroid 2008 RG1 passed by the Earth at a distance of about 10 210 000 km (26.56 times the average distance between the Earth and the Moon, or 6.8% of the average distance between the Sun and the Earth), slightly after 10.35 pm GMT on Monday 25 August 2014. There was no danger of the asteroid hitting us, though were it to do so it would have presented a serious threat. 2008 RG1 has an estimated equivalent diameter of 140-430 m (i.e. it is estimated that a spherical object with the same volume would be 140-430 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 with an energy equivalent to about 130-4000 megatons of TNT (roughly 7500-235 000 times the energy of the Hiroshima bomb). Such an event would result in a crater between 2.25 and 7 km across, cause devastation on a global scale and would have the potential to affect the climate globally for decades after the impact event.
The calculated orbit of 2008 RG1. JPL Small Body Database Browser.
2008 RG1 was discovered on 4 September 2008 by the Massachusetts Institute of Technology's Lincoln Near Earth Asteroid Research Laboratory in Socorro, New Mexico. The designation 2008 RG1 implies that it was the 32nd asteroid (asteroid G1) discovered in the first half of September 2008 (period 2008 R).
2008 RG1 has a 551 day year orbital period and an eccentric orbit tilted at an angle of 13° to the plane of the Solar System, which takes it from 0.73 AU from the Sun (i.e. 73% of the average distance at which the Earth orbits the Sun and slightly outside the orbit of Venus) to 1.90 AU from the Sun (i.e. 190% 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). This means that close encounters between the asteroid and Earth are fairly common, most recent having occurred in August 2011 and the next predicted in August 2017. As an asteroid on a trajectory which brings it extremely close to Earth which is large enough to cause serious harm should it collide with Earth it is also classified as a Potentially Hazardous Asteroid.
See also...
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