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Meteor shower from the 'Twilight Zone'
By Richard Stenger
(CNN) -- Meteors known for their graceful, slow and bright yellow trails put on a display each December, but the dependable celestial shower springs from a rather strange source. The Geminids, which peaked over the weekend, do not come from cometary debris like most meteors. Rather, they originate from a mysterious object in the inner solar system that defies astronomical classification. "I enjoy the Geminids because they come from the Twilight Zone," joked NASA scientist Bill Cooke in a statement. Conventional meteor showers like the Leonids and Perseids come from comets, boulders of ice and rock that shed material when they approach the sun, creating picturesque tails and leaving clouds of gas and dust. When the Earth plows through such debris patches, minuscule comet fragments burn up in the atmosphere and light up the nighttime sky. But the Geminids are linked to 3200 Phaethon, an inner solar system object that lacks many qualities of comets in the neighborhood. "3200 Phaethon doesn't sprout a tail when it comes close to the sun. It doesn't have a halo or a coma," Cooke said in a NASA bulletin. "In fact, based on its orbit and the way it reflects sunlight, it seems much more like an asteroid," he said. But 3200 Phaethon's size and association with a meteor shower give it some comet-like qualities, boosting speculation that 3200 Phaethon is a combination asteroid-comet. "It has become quite obvious in recent years that our nomenclature in astronomy is not keeping pace with our discoveries," Cooke said. "We like to place objects in neat, well-defined categories even though Mother Nature makes no such distinctions," he said, citing debate over whether Pluto is a small planet or a large Kuiper Belt Object, one of many giant ice chunks beyond the planets. 'Rocky comet corpse'Astronomers theorize that 3200 Phaethon is the remnant of a comet that gradually lost its ice supply after repeated brushes with the sizzling heat of the sun. "Now all that's left is a rocky comet corpse," Cooke said. Regardless of the source, the Geminids provide one of the most consistent annual meteor shows. They hardly match the Leonids and Perseids at their best, which during good years produce thousands of shooting stars an hour. But the latter two are much sporadic from year to year. And the Geminids are growing in intensity each year. During the peak hours Saturday, more than 100 meteors an hour were expected for viewers in ideal conditions -- dark and clear skies. The Geminids gradually increased in the weeks before the main event. But within days afterward, meteor counts will plummet.
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