Nov. 8, 2011 at 5:53 PM ET
Astronomers watched the asteroid 2005 YU55 spin as it zoomed harmlessly past Earth, and everybody else was looking over their shoulders. You can expect to see a huge pile of pictures now that the coal-dark space rock has passed by.
Even before the closest pass, NASA's Jet Propulsion Laboratory provided a six-frame "movie" based on radar data acquired by the Goldstone radio telescope on Monday. This sequence was captured from a distance of 860,000 miles (1.38 million kilometers).
The closest approach to Earth came at 6:28 p.m. ET Tuesday, when the quarter-mile-wide (400-meter-wide) asteroid slipped just barely within the orbit of the moon at a distance of 198,000 miles (319,000 kilometers). YU55 is due to come closest to the moon at 2:14 a.m. ET Wednesday, NASA said.
Neither the moon nor Earth was at risk during this flyby, but the information gathered this time around could help astronomers know what they're dealing with during potentially riskier encounters.
Here's a parting shot of YU55 from the 25-inch telescope at the Clay Center Observatory in Massachusetts, which tracked the asteroid as it swept past at 29,000 mph:
In a Twitter update, NASA said that YU55 will make its next Earth flyby in 2015, "but at a greater distance than today." Today's encounter wasn't close enough to perturb the near-Earth asteroid's orbit, but experts are wondering whether a close flyby of Venus in 2029 will change its orbital path slightly.
Even if that Venus encounter does cause a change, Earth is in no danger from this particular space rock, at least for the next 100 years or so. Which is a good thing. If an object the size of YU55 were to hit land, experts say it would blast a 4-mile-wide, 1,700-foot-deep crater and set off a 7.0 earthquake. If it hit at sea, it would create a catastrophic tsunami with 70-foot-high waves.
The last time an asteroid as big as YU55 came this close was in 1976, and the next time will be in 2028 — or could it be sooner? Scientists recently estimated that thousands of asteroids around the size of YU55 remain to be discovered, so learning about this rock's composition and motion could help us deal with many other rocks to come.
YU55 is particularly interesting because it has a high carbon content, which makes it coal-black. Such carbonaceous chondrites have been found to contain amino acids, and may have played a role in the origin of life on Earth. NASA's Osiris-Rex mission, due for launch in 2016, will target a carbonaceous asteroid called 1999 RQ36 and try to bring a sample back to Earth for study.
NASA's current space vision calls for sending astronauts to a near-Earth asteroid sometime in the mid-2020s, and the head of NASA's Near Earth Object Program, Don Yeomans, said that if he got the chance to decide the destination, he'd pick a carbon-bearing rock like YU55.
"This would be an ideal object," he told The Associated Press.
Still more about the encounter:
Correction for 3:45 p.m. ET: I originally wrote that the Clay Center Observatory's telescope was a 15-incher, but it's actually a 25-incher.
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