Some astronomical questions are mysteries with a capital M -- questions about giant galaxies, exploding stars, and the size and fate of the universe. But others have a little m -- mysteries that aren't as grand, but that are still fun to look into.
Two of the "little" mysteries are related to the Geminid meteor shower, which is at its best this weekend. The gibbous Moon gets in the way, though, so only the brightest of the "shooting stars" will shine through.
The first mystery was the shower's origin.
The Geminids first appeared in the 1860s. Most other meteor showers have been around for centuries, so the appearance of a new one was unusual. And over the decades, the shower kept getting better, with more meteors every year.
But no one could find the source of the Geminids. Meteor showers occur when Earth flies through the orbital path of a comet, sweeping up bits of debris left in the comet's wake. But no known comet matched the Geminids.
Then in 1983, astronomers discovered an object that appeared to be a rocky asteroid, not an icy comet. But its orbit matched that of the Geminid shower, so it had to be the source of the meteors.
And that raised the second mystery: Is the object, known as 3200 Phaethon, really an asteroid? It's possible that it's the burned-out core of a comet that lost its ice. If so, then perhaps other asteroids are really ex-comets as well -- another little mystery for astronomers to ponder.
Script by Damond Benningfield, Copyright 2008
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