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The Geminid shower occurs when Earth flies through the path of 3200 Phaethon, a rocky asteroid that sheds bits of debris as it orbits the Sun. Some of these small bits of rock streak into Earth’s atmosphere and explode as bursts of incandescent gas, forming the streaks of light known as meteors.

Unusual Parent
Most meteor showers are spawned by icy comets. As they near the Sun, some of their ice vaporizes and puffs away into space. That lets small particles of rock and ice escape, forming a cloud around the comet. Over time, the material spreads out along the comet’s orbit, forming a thin cloud of debris. When Earth flies through this path, it sweeps up some of the grains of rock and ice, which form meteors.

Phaethon, however, is a mountain-sized chunk of rock, not a comet. Scientists suspect that it began life as a comet, but after many passages close to the Sun, all of its frozen gases boiled away, leaving only bare rock.

The Name
Meteor showers are named not for their parent objects, but for the constellation in which they appear -- in this case, Gemini, the twins. That does not mean, however, that you must look at Gemini to see the meteors. They can streak across any part of the sky. But if you traced their paths back across the sky, all the meteors would appear to “rain” from Gemini.

A view of the shower’s ‘radiant’ point in Gemini. [NASA]

Getting a Look
This should be a good year for the Geminids. Phaethon is passing just 11 million miles from Earth a few days before the shower, so it should bring a fresh supply of particles. And the Moon sets in the evening, leaving most of the night for meteor watching. The best view should come in the early morning hours of December 14, when you could see up to several dozen Geminids streaking across the sky every hour.

To see them, though, you must get away from city lights, which can overpower all but the brightest meteors. A national or state park might be a good choice. Find a spot with an unobstructed view of the sky, and bundle up against the cold. Then enjoy the fireworks!

For more information, see our 2007 Meteor Showers page.

-- Damond Benningfield