Washington: An asteroid will safely pass about three times the distance of the Earth to the Moon on Jan 26, NASA reported.
From its reflected brightness, astronomers estimate that the asteroid designated "2004 BL86" is about a third of a mile (0.5 km) in size. Its exact size is yet to be determined.
The flyby of 2004 BL86 will be the closest by any known space rock this large until asteroid "1999 AN10" flies past Earth in 2027.
At the time of its closest approach January 26, the asteroid will be approximately 1.2 million km from the Earth. At its current speed of 16 km a second, it would take barely 26 hours to hit the Earth were it on collision course.
The power of its impact could destroy a large region like most of Europe or cause a devastating tsunami that would wipe out entire continental coastlines, experts say.
"Jan 26 will be the closest asteroid '2004 BL86' will get to the Earth for at least the next 200 years," said Don Yeomans from NASA's Jet Propulsion Laboratory in Pasadena, California.
"And while it poses no threat to Earth for the foreseeable future, it's a relatively close approach by a relatively large asteroid, so it provides us a unique opportunity to observe and learn more."
NASA scientists plan to learn more about '2004 BL86' by observing it with microwaves.
Asteroid "2004 BL86" was initially discovered Jan 30, 2004, by a telescope of the Lincoln Near-Earth Asteroid Research (LINEAR) survey in White Sands, New Mexico.
The asteroid is expected to be observable to amateur astronomers with small telescopes and strong binoculars.