"We got a rock."

Remember It's the Great Pumpkin, Charlie Brown?  Each house the kids go to for trick or treating grants plenty of candy to brag over and everybody's feeling good...until Charlie Brown says, "I got a rock"?  Well our rock for Halloween came about a week late but it got here.

An asteroid the size of an aircraft carrier came within 202,000 miles of Earth yesterday.  That's within the Moon's orbit.  Despite such proximity, Asteroid 2000 YU55 never posed any real threat to us.  If anything, scientists at NASA, astronomical observatories, and anyone with an interest in space science have been looking forward to this close approach.  As one said on Space.com:

"We would really like to characterize it as much as possible, and learn about its past and about its future," said Marina Brozovic, a scientist with NASA's Near-Earth Object Office at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., before today's flyby. "I really can't wait to see the images."

Much will be gleaned in terms of the orbits of asteroids and how we can be better able to track such objects in space.  After, this buzz-by should teach us that there are monster planet-killers out there and there is no reason to believe that there couldn't be one with our name on it.  Meg Urry, the chairwoman of the Department of Physics at Yale University, wrote an opinion piece for CNN pointing out the very real risk of an asteroid strike.  She admits that though rocks the size of the one that is thought to have killed off the dinosaurs are fairly rare, an asteroid the size of YU55 would still cause considerable damage to our planet.  Since large rocks have pelted both Earth and the Moon in centuries past, there is no reason we won't have to deal with a threat in the future.   This is no time to sit around in a kef and believe it could never happen to us.

But much will be learned from this encounter.  The downside is that the asteroid will not be visible to the naked eye as its dark surface will not reflect enough light to make its presence known.  Amateur skywatchers with telescopes might be able to catch a glimpse before YU55 heads back out into deep space.


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