Asteroid (448003) 2008 DE passed by the Earth at a distance of about 18 880 000 km (49.1 times the average distance between the Earth and the Moon, or 12.6% of the distance between the Earth and the Sun), slightly after 0.30 am GMT on Sunday 28 April 2017. There was no danger of the asteroid hitting us, though were it to do so it would have presented a considerable threat. (448003) 2008 DE has an estimated equivalent diameter of 240-750 m (i.e. it is estimated that a spherical object with the same volume would be 240-750 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 32 000-1 175 000 times as powerful as the Hiroshima bomb. Such an impact would result in an impact crater about 3.5-11 km in diameter and devastation on a global scale, as well as climatic effects that would last decades or even centuries.
The calculated orbit of (448003) 2008 DE. Minor Planet Center.
(448003) 2008 DE was discovered on 12 February 2008 by the University of Arizona's Catalina Sky Survey, which is located in the Catalina Mountains north of Tucson. The designation 2008 DE implies that it was the fifth asteroid (asteroid E) discovered in the second half of February 2008 (period 2008 D), while the longer designation (448003) indicates that it was the 448 003rd asteroid discovered overall (asteroids are not given this longer designation immediately, to ensure that numbered objects are genuine asteroids that have not been previously described).
(448003) 2008 DE has an 820 day orbital period and an eccentric orbit tilted at an angle of 14.8° to the plane of the Solar System, which takes it from 1.005 AU from the Sun (i.e. 100.5% of he average distance at which the Earth orbits the Sun) to 2.43 AU from the Sun (i.e. 243% of the average distance at which the Earth orbits the Sun, and considerably outside the orbit of the planet Mars). It is therefore classed as an Amor Group Asteroid (an asteroid which comes close to the Earth, but which is always outside the Earth's orbit). This means that close encounters between the asteroid and Earth are fairly common, with the most recent having occurred in May 2008 next predicted in April 2026. As an asteroid probably larger than 150 m in diameter that occasionally comes within 0.05 AU of the Earth, (448003) 2008 DE is also classified as a Potentially Hazardous Asteroid (it comes no closer to the Sun than 100.5% of the average distance at which the Earth orbit's the Sun, but the Earth's orbit is not completely circular).
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