Sky Talk December 2009: The Geminid Meteor Shower

December brings skywatchers one of the year’s richest and most dependable displays of “shooting stars” — the Geminids. They’re named for the constellation from which they appear to radiate or “shoot” across the sky. But unlike most other meteor displays whose host constellations typically don’t rise until the hours after midnight, this one is already above the horizon after dark, making this shower ideal for early evening viewing.

One of the most-observed annual meteor showers is the Geminids due to its consistent intensity of as many as 100 shooting stars per hour during its peak activity as seen under a dark sky. They appear to radiate from near the bright star Castor, one of the two “Twin Stars” marking Gemini, the mythological twins (the other being the star Pollux). To find them, set your Scientifics Star and Planet Locator (#30092-27) for about 8:00 p.m. around mid-December and face northeast, where you’ll see the pair just clearing the horizon. The shower will be best viewed on the late evening of November 13th into the early morning hours of the 14th, with maximum activity expected around 2:00 a.m. EST. The Moon will be nearing its New phase on the 16th, so will offer no interference to visibility of this year’s display.

If you watch through the evening hours, you’ll notice that the number of meteors seen increases as the night grows later and Gemini continues to rise ever-higher in the sky. But there’s also another less obvious factor at work here. In the evening, we’re on the side of our planet “facing away” from the direction the meteors are approaching and so they have to “catch up” with us. But after midnight we’re turned into the direction of the radiant, causing them to slam into the atmosphere at much higher speeds and resulting in many more of them being seen. So the later you observe up to the time of the peak, the more activity you’ll see.

Observing shooting stars is basically a naked-eye activity in order to survey as large an area of sky as possible, a helpful technique here being to face east toward the radiant and concentrate your attention on the sky overhead — preferably comfortably reclining on a lawnchair. Use of your Celestron SkyMaster binoculars from Edmund (#30311-02) is also encouraged for following the smoke trails or “trains” often left behind by many of the brighter meteors. And there’s even something here for telescope users as well. Using a low-power, wide-field glass such as the Edmund Astroscan (#30050-01), you may well see faint streaks of light passing through the eyepiece from time-to-time while observing other sights around the sky. Known as telescopic meteors, these are also Geminids that in most cases are much too faint to be seen with the eye alone. Pointing your telescope or binoculars at the radiant itself, you may even see meteors coming directly at you — appearing from out of nowhere as brightening stars. And, if you’re really lucky, you may even experience the ultimate thrill of having a bright naked-eye meteor suddenly flash across the eyepiece field in a blinding burst of light!

–James Mullaney
Former assistant editor at Sky & Telescope magazine and author of eight books on stargazing.


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