The annual Geminid meteor shower, which peaks the night of December 13/14, is typically one of the best of the year. Occurring less than a month after the Leonids, the Geminid shower generally features brighter meteors. In 2012, New Moon occurs December 13, so it will have no effect on viewing.
The Geminids are so named because if you trace all the meteor trails backward, they would converge within the boundaries of the constellation Gemini the Twins. This point, called the radiant, lies approximately 3° northwest of the 1st-magnitude star Castor.
Geminid meteors are relatively slow moving, and many leave smoke trails that can last a number of seconds. In 2012, the shower will be active from about December 4 to 17, but the peak (the best time to see them) occurs the night of December 13 and the morning of December 14. The Geminid meteor shower has a broad peak, so observers should see an excellent show all night.
According to Astronomy Senior Editor Richard Talcott, “The Geminid shower is one of the most active of any year and usually produces a good percentage of bright meteors, so it's worth watching even under less-than-favorable conditions. This year, however, conditions are excellent.”
As the radiant approaches the zenith (the overhead point) soon after midnight, observers under dark skies should see 80 to 120 meteors per hour. This rate makes the Geminid shower one of the two best of the year, right up there with August's Perseid meteor shower. And with New Moon occurring at the peak, December's shower should surpass the Perseids this year.
Meteors are small particles of rock and metal that Earth runs into while orbiting the Sun. In space, astronomers call these particles meteoroids. When they burn up in the atmosphere, they become meteors. If they survive the fiery ordeal through our thick blanket of air and land on Earth, we then classify them as meteorites. No meteorites come from meteor showers — the particles are too small.
Most meteor showers trace their origins to comets. When a comet swings around the Sun, it leaves a trail of debris (small meteoroids). Sometimes, the orbit of this debris crosses Earth's orbit. When Earth runs into this stream of particles, we experience a meteor shower.
In 1983, after more than a century of searching for the Geminid shower's parent comet (astronomers first noted the Geminids in 1862), scientists realized that the asteroid 3200 Phaeton has an orbit almost identical to the Geminid meteoroid stream. Further study confirmed that the asteroid was the progenitor of the Geminid meteor shower.
To maximize the chances of seeing meteors, choose a dark site. “'Dark' means at least 40 miles from a major city,” Talcott says. And you can leave your telescope home. “You don't need optical aid (a telescope or binoculars) to observe the Geminids. Your eyes alone work best for meteor showers because they don't restrict your field of view.” That said, binoculars will help you follow any long-lived smoke trails. After sunset, face generally east and look halfway up. Around midnight, look generally overhead. After midnight, when you're most likely to see the most shooting stars, move your gaze to high in the western sky.
Suggested gear includes a lawn chair, lots of warm clothing, cookies or fruit, and a warm, nonalcoholic beverage. Alcohol interferes with the eye's dark adaptation as well as the visual perception of events.