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Geminids Meteor Shower
Geminids Meteor Shower (click to enlarge)

Geminids Meteor Shower
Date: 13 Dec 1985

Star trails and a Geminid meteor over Brasstown Bald Mountain, Ga, in 1985.

The Geminids are not ordinary meteors. While most meteor showers come from comets, Geminids come from an asteroid -- a near-Earth object named 3200 Phaethon.

Comets create meteor showers by evaporating. When a comet flies close to the sun, intense heat vaporizes the comet's "dirty ice" resulting in high-speed jets of comet dust that spew into interplanetary space. When a speck of this comet dust hits Earth's atmosphere, it disintegrates in a bright flash of light -- a meteor.

Asteroids don't normally spew dust into space. Evidence suggests 3200 Phaethon used to be a comet. Phaethon's orbit is highly elliptical, like the orbit of a typical comet and brings Phaethon extremely close to the sun, twice as close as Mercury itself. Every 1.4 years, Phaethon swoops through the inner solar system where repeated blasts of solar heat could easily reduce a comet to the rocky skeleton we see today.

If this scenario is correct, Phaethon may have produced many rich streams of dust that spent hundreds or thousands of years drifting toward Earth until the first Geminid meteors appeared during the U.S. Civil War. Since then, Geminids have been a regular shower peaking every year in mid-December.

Credit: Jimmy Westlake

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