December 7, 2005
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An old, reliable meteor shower is heading our way. The annual Geminid shower should reach its peak activity late on the night of December 13–14, 2005: late Tuesday night and early Wednesday morning. However, the glare of the nearly full Moon will hide all but the brightest meteors.
Along with the better-known Perseids of August, the Geminids are the strongest of the reliable annual meteor showers — those that hardly change from year to year. Sky & Telescope magazine predicts that late on the peak night, you might see a "shooting star" through the moonlight every 5 to 10 minutes on average.
The time to watch will be anytime from about 10 p.m. Tuesday evening, December 13th, until the first light of dawn on Wednesday morning the 14th. You'll need no equipment but your eyes. Find a spot with an open view of the sky and no bright lights nearby. Bring a reclining lawn chair, bundle up warmly, and bring a sleeping bag; clear nights get very cold.
"Arrange the chair so the Moon is behind you out of sight, lie back, and watch the stars," says Sky & Telescope senior editor Alan MacRobert. "Be patient."
In years when there's no Moon on the peak night, meteor watchers under dark skies can see Geminids as often as once a minute. This year only the less frequent bright ones will be visible. But the best of these may sail across the heavens for several seconds, leaving brief trains of glowing smoke.
If you trace each meteor's direction of flight backward far enough across the sky, you'll find that the imaginary line you're drawing crosses a spot in the constellation Gemini near the stars Castor and Pollux. This spot is the shower's radiant, the perspective point from which all the Geminids would appear to come if you could see them approaching from the far distance. The radiant is well up in the east by 10 p.m., nearly overhead around 2 a.m., and high in the west by the first light of dawn. But you don't have to look there. Just watch whatever part of your sky offers the darkest view.
The Geminid shower is active for several days, not just on its peak night. You may see a few meteors per hour for two or three nights beforehand and one night after.
The Geminid meteoroids (particles) are tiny, sand-grain- to pea-size bits of rocky debris shed from a small asteroid named Phaethon. Over the centuries these bits have spread all along the asteroid's orbit to form a sparse, moving "river of rubble" hundreds of millions of miles long. Earth's own annual orbit around the Sun carries us through this stream of
particles every mid-December.
The particles are traveling 22 miles per second with respect to Earth at the place in space where we encounter them. So when one of them strikes Earth's upper atmosphere (about 50 to 80 miles up), air friction vaporizes it in a quick, white-hot streak.
More information on meteor showers and how to watch them is available online at SkyandTelescope.com in Observing > Celestial Objects > Meteors.
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