An asteroid the size of an aircraft carrier passed close to the Earth on Tuesday, professional and amateur astronomers reported.
With a diameter estimated at 400 meters - roughly a quarter of a mile - Asteroid 2005 YU 55 is the biggest asteroid to make a close pass by Earth since 1976.
YU 55 is believed to be one of the more common type, carbon-rich asteroids, albeit a large one. Its ancient rocks may contain water, metals and other materials that could be useful for space explorers.
During YU 55's closest approach – which occurred at 6:28 p.m. EST, it passed inside the orbit of the moon at 200,000 miles above the Earth – the black asteroid was travelling at 30,000 miles per hour.
The asteroid, which posed no threat during its pass, was primarily a spectacle for sky watchers.
"It was pretty easy to find," astronomer Ronald Dantowitz, director of the student-run Clay Center Observatory in Brookline, Massachusetts, told Reuters. "It's moving differently than the stars are moving. It looks like a giant rock floating through space."
Astronomers believe YU 55 has been visiting Earth for thousands of years, having been shoved out the Solar System's main asteroid belt between Mars and Jupiter by gravitational forces.
Computer models simulating the asteroid's path for the next 100 years show there is no chance it will hit Earth or the moon during that time, said Don Yeomans with NASA's Jet Propulsion Laboratory in Pasadena, California.
NASA's next human space venture beyond the International Space Station is a mission to an asteroid, targeted for 2025.