Image of asteroid's path inside lunar orbit shows Earth's gravitational effect on the object.
A 100-foot diameter asteroid will pass within 26,500 miles of Earth on Thursday evening, the closest-ever brush on record by a space rock, NASA astronomers said.
The asteroid's close flyby, first spied late Monday, poses no risk, NASA astronomers stressed.
''It's a guaranteed miss,'' astronomer Paul Chodas, of the near-Earth object office at NASA's Jet Propulsion Laboratory, said Wednesday.
The asteroid, 2004 FH, was expected to make its closest approach at 5:08 p.m. EST, streaking over the southern Atlantic Ocean. It should be visible through binoculars to stargazers across the southern hemisphere, as well as throughout Asia and Europe, said astronomer Steve Chesley, also of JPL.
Professional astronomers around the globe scrambled Wednesday to prepare for the flyby, which could provide an unprecedented chance to get a close look at the asteroid, he added. The asteroid will pass within the moon's orbit.
Similarly sized asteroids are believed to come as close to Earth on average once every two years, but have always escaped detection.
''The important thing is not that it's happening, but that we detected it,'' Chesley said.
Astronomers found the asteroid late Monday during a routine survey carried out with a pair of telescopes in New Mexico funded by the National Aeronautics and Space Administration. Follow-up observations on Tuesday allowed them to pinpoint its orbit.
''It immediately became clear it would pass very close by the Earth,'' Chesley said.
Astronomers have not ruled out that the asteroid and our planet could meet again sometime in the future. If the two were to collide, the asteroid likely would disintegrate in the atmosphere, Chesley said.
Dave
