Asteroid 2005 YU55 Passes Earth Within Moon's Orbit
AP — LOS ANGELES -- An asteroid as big as an aircraft carrier zipped by Earth on Tuesday in the closest encounter by such a massive space rock in more than three decades. Scientists ruled out any chance of a collision but turned their telescopes skyward to learn more about the object known as 2005 YU55.
Its closest approach to Earth was pegged at a distance of 202,000 miles at 6:28 p.m. EST. That's just inside the moon's orbit; the average distance between Earth and the moon is 239,000 miles.
The last time a large cosmic interloper came that close to Earth was in 1976, and experts say it won't happen again until 2028.
Scientists at NASA's Deep Space Network in the California desert have tracked the quarter-mile-wide asteroid since last week as it approached from the direction of the sun at 29,000 mph.
Astronomers and amateur skygazers around the world kept watch, too.
The Clay Center Observatory in Brookline, Mass., planned an all-night viewing party so children and parents could peer through research-grade telescopes and listen to lectures. The asteroid can't be detected with the naked eye.
For those without a telescope, the observatory streamed video of the flyby live on Ustream, attracting several thousand viewers. The asteroid appeared as a white dot against a backdrop of stars.
"It's a fantastic opportunity to educate the public that there are things out in space that we need to be aware of," including this latest flyby, said observatory director Ron Dantowitz.
Dantowitz added: "It will miss the Earth. We try to mention that in every breath."
If an asteroid that size would hit the planet, Purdue University professor Jay Melosh calculated the consequences. The impact would carve a crater four miles across and 1,700 feet deep. And if it slammed into the ocean, it would trigger 70-foot-high tsunami waves.
Since its discovery six years ago, scientists have been monitoring the spherical, coal-colored asteroid as it slowly spins through space and were confident it posed no danger.
Asteroids are leftovers from the formation of the solar system some 4.5 billion years ago. Scientists believe their growth was stunted by Jupiter's gravitational pull and never had the chance to become full-fledged planets. Pieces of asteroids periodically break off and make fiery plunges through the atmosphere as meteorites.
Don Yeomans, who heads NASA's Near Earth Object Program, said 2005 YU55 is the type of asteroid that humans may want to visit because it contains carbon-based materials and possibly frozen water.
With the space shuttle program retired, the Obama administration wants astronauts to land on an asteroid as a stepping stone to Mars.
"This would be an ideal object," Yeomans said.
PHOTOS: Images of Asteroids
In this handout from NASA, the giant asteroid Vesta is seen in an image taken from the NASA Dawn spacecraft about 3,200 miles above the surface July 24, 2011 in Space. (Photo by NASA/JPL-Caltec via Getty Images)
This Feb. 14, 2000 photo provided by NASA shows the north pole of the asteroid Eros. The crater seen on the surface of Eros measures 4 miles across. (AP Photo/NASA)
This handout image provided by the European Space Agency, transmitted by the space craft Rosetta, shows the asteroid Lutetia at closest approach July 10, 2010 between Mars and Jupiter in outer space. (Photo by ESA 2010 MPS for OSIRIS Team via Getty Images)
This undated artist concept released by NASA and the Jet Propulsion Laboratory shows the Dawn spacecraft with Ceres and Vesta seen in the background. The spacecraft was captured into orbit around the massive asteroid Vesta after a 1.7 billion-mile journey and is preparing to begin a study of a surface that may date to the earliest era of the solar system, the space agency said Monday, July 18, 2011, in Pasadena, Calif. (AP Photo/William K. Hartmann/UCLA/NASA, JET PROPULSION LABORATORY)
This handout photo illustration provided by the European Space Agency, transmitted by the space craft Rosetta, shows the final sequence of images before the closest approach of the asteroid Lutetia July 10, 2010 between Mars and Jupiter in outer space. (Photo by ESA 2010 MPS for OSIRIS Team via Getty Images)
This handout image provided by the European Space Agency, transmitted by the space craft Rosetta, shows a close-up view of a possible landslide and boulders at the highest resolution on the asteroid Lutetia July 10, 2010 between Mars and Jupiter in outer space. (Photo by ESA 2010 MPS for OSIRIS Team via Getty Images)
This artist's concept provided by NASA illustrates the first known Earth Trojan asteroid, discovered by NEOWISE, the asteroid-hunting portion of NASA's WISE mission. The asteroid is shown in gray and its extreme orbit is shown in green. Earth's orbit around the sun is indicated by blue dots. The objects are not drawn to scale. The asteroid's orbit is well defined and for at least the next 100 years, it will not come closer to Earth than 15 million miles (24 million kilometers). (AP Photo/NASA - Paul Wiegert)
Computer modeling shows that the parent object of asteroid (298) Baptistina, which was approximately 170-kilometers in diameter with characteristics similar to carbonaceous chondrite meteorites, was disrupted 160 million years ago when it was hit by another asteroid estimated to be 60-kilometres in diameter.The extinction of the dinosaurs 65 million years ago can be traced to a collision between two monster rocks in the asteroid belt nearly 100 million years earlier, scientists reported on September 5, 2007. The two pictures on the right show remnants of the collision impacting the Earth and Moon. (DON DAVIS/AFP/Getty Images)
This image of the Asteroid Vesta, released by NASA/Jet Propulsion Laboratory on Monday, August 1, 2011, was captured by the Dawn spacecraft on July 24, 2011 at a distance of 3,200 miles (5,200 kilometers). (AP Photo/NASA, Jet Propulsion Laboratory)
This July 23, 2011 image of the Asteroid Vesta, released by NASA/JPL, was captured by the Dawn spacecraft at a distance of 3,200 miles (5,200 kilometers). (AP Photo/ NASA/JPL)
This undated artist rendition released by NASA/JPL shows the Dawn spacecraft orbiting the asteroid Vesta. (AP Photo/NASA/JPL)
This image released by NASA/JPL on Thursday July 28, 2011 shows an image of the dark side of Vesta asteroid captured by NASA'S Dawn spacecraft on July 23, 2011, and taken from a distance of about 3,200 miles (5,200 kilometers) away from the giant asteroid. (AP Photo/NASA/JPL)
This image of the Asteroid Vesta, released by the Jet Propulsion Laboratory in Pasadena, Calif., Monday, July 18, 2011, was captured by the Dawn spacecraft on July 17, 2011. The image was taken from a distance of about 9,500 miles (15,000 kilometers) away from the proto planet Vesta. (AP Photo/ NASA/JPL)
This image of the Asteroid Vesta, released by the Jet Propulsion Laboratory in Pasadena, Calif., Monday, July 18, 2011, was captured by the Dawn spacecraft on July 1, 2011. The image was taken from a distance of about 62,000 miles (100,000 kilometers) away from the protoplanet Vesta. Each pixel in the image corresponds to roughly 5.8 miles. (AP Photo/ NASA)