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11/13/2001

Leonids

Filed under:General — eric @ 1:11 am

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The Leonid meteor shower is upon us this weekend. The cool dry air usually makes this shower worth watching, but sometimes this shower turns into a full-fledged storm. In 1966, for example, an estimated 500,000 meteors were seen in an hour’s time. I can’t imagine that; it would be like watching a rather intense fireworks display, I suppose. It has always been a tricky affair predicting the intensity of these things. It was known that they are caused by the earth travelling through the debris field of a comet, the remnants of the cometary tail, but we didn’t know much about the debris itself. It was supposed that it was a cloud of dust, and if we were lucky enough to travel through a dense part of the cloud, we saw a good show. In the last few years, though, a few astronomers have made a breakthrough. We now know that a comet leaves behind a small but dense trail behind it. With each orbit, it leaves behind another track, but not exactly in the same place as the last, so the net effect is rather like a grape vine wreath. The tracks do eventually dissipate, but the last several hundred years’ worth are still there. These astronomers have now mapped out the precise positions of these trails and can predict amazingly well when we will cross one of them. Usually, we go through mostly empty space, hitting the dissipated dust. This year, though, we’ll go straight through the heart of one of the trails. It’s an older one, so the models differ on exactly how many meteors we’ll see, but the range is (over my new house) between 500 and 2000 an hour. In a typical year, we see maybe 20 an hour, so this should be quite a show. Check the predictions for your area, set your alarm clock for early Sunday morning, and join me outside!