Tuesday, October 7, 2008

Its a Shooting Gallery Out There!

It has been the plot line for more than a couple high-profile movies in recent years - nerdy astronomers on remote mountaintops discover an asteroid or comet will hit the earth a couple years from now and it is up to NASA to send a crew of astronomers to deflect or destroy it before life on earth is destroyed.

The truth is that space chunks hit us all the time but yesterday was the FIRST TIME that astronomers sighted an object before it struck the earth. Yes, the earth was struck last night - did you feel it? Likely not as it landed in Sudan, Africa about 9:45pm central time. Predicted to be a couple meters in diameter (less than 10 feet), it is unlikely to do any damage in that remote area, but it likely released energy equivalent to a kiloton (one thousand tons) of conventional explosives, likely all of it in the upper atmosphere. The image here was taken in Italy with about 6 hours to go before impact. The telescope followed the chunk (I hesitate to call it an asteroid or meteoroid), so the stars appear trailed.

So how much warning did the astronomers give us? Well, as I said, this was the first time we got any warning, and in this case we got something less than 24 hours advance notice. A little too short to do anything about it, but I was amazed that in those 24 hours that the network was in place to allow orbits to be calculated and refinements to be made as additional observations come in. In all, about 25 observations were made from observatories around the world, and believe it or not, when an object is that close to us (the discovery in Arizona (!) came when it was about the moon's distance from us) parallax effects make it difficult to track. If someone from Europe and the US were looking at the moon at the same time, the position on the sky could differ by up to 2 degrees because of the separation of the observers...

Believe it or not, there are only a couple dedicated programs looking for space rocks that may collide with us, and they run on shoestring budgets. If they had as much money as those movies had brought in we would be in much better shape! There are projects down the road that will do a much better job at finding these, but that is for a future post!

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