An asteroid the size of an aircraft carrier passed within the moon's orbit Tuesday, the closest approach by an object that large in more than 30 years.
Asteroid 2005 YU55 passed within 202,000 miles of Earth -- about four-fifths of the distance to the moon -- at 6:28 p.m. Tuesday, NASA said.
Marina Brozovic, a researcher at NASA's Jet Propulsion Laboratory in California, said the space agency was able to train a great deal of high-powered instruments -- including the massive radio telescope at Arecibo, Puerto Rico -- on the asteroid as it approached.
"This is a rare event, and we learned a lot," Brozovic told CNN.
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Though the space agency classified the asteroid as a "potentially hazardous object," it posed no threat of a collision, according to NASA's Near Earth Object Program.
If the asteroid had crashed into Earth, it could have caused a 4,000-megaton blast and a magnitude 7.0 earthquake, according to scientists at Purdue University. If it fell into the ocean, it could have caused a 70-foot-high tsunami within 60 miles of the crash site, the experts said.
The last time a space rock in the same league as 2005 YU55 passed as close to Earth was in 1976, NASA said. The next similar encounter is projected for 2028, Brozovic said.
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As the object neared Earth, NASA studied the asteroid with the Goldstone radar antennas in California's Mojave Desert. Goldstone antennas are very sensitive radio telescopes used to investigate quasars, radar mapping of planets and comets.
Scientists plan to reconstruct the shape of the asteroid with a resolution as fine as 13 feet (4 meters) using the antennas.
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The approach also provides a rare opportunity for amateur astronomers to directly observe an asteroid with optical telescopes. But because the object is so dark, NASA said stargazers would need a telescope with an aperture of 6 inches (15cm) or larger to see it.
"It's visible across North America in the ensuing hours, dim at 11th or 12th magnitude and moving fast," Sky & Telescope magazine said.