Near-Earth asteroid 2005 YU55 - on the list of potentially dangerous asteroids - was observed by the Arecibo telescope April 19 as it passed about 2,4 million km from the Earth (about 6x the distance to the moon).

The Arecibo Observatory, located in Puerto Rico, is part of the National Astronomy and Ionosphere Center, managed by Cornell on behalf of the National Science Foundation.

The Arecibo radar imaging of 2005 YU55 showed, that the asteroid is about 400 meters in size and twice as large as previously estimated.

As they tracked the asteroid, Cornell researcher Ellen Howell and colleagues, including Cornell researcher Patrick Taylor, used high-precision radar to reduce uncertainties about its orbit by 50%. This improvement eliminated any possibility of an impact with the Earth for the next 100 years, and the asteroid was removed from the "Risk Page" maintained by NASA's Near-Earth Object Program Office.

After circling the sun, 2005 YU55 will next approach the Earth to about 0,8 lunar distances Nov. 8, 2011. It will pose no impact hazard.

Robert McMillan of the Spacewatch asteroid detection program, discovered the asteroid on Dec. 28 2005.

NASA has indicated that it intends to provide support to the Arecibo radar program if that funding remains in the budget.

Source: Cornell University