The Geminids – one of the year’s most prominent meteor showers – radiate from near Castor, the second brightest star in the constellation Gemini. Many seasoned meteor watchers believe the Geminid shower is better than the August Perseids, and for a good reason.
The Geminid radiant is nearly as far from the Sun as one can get in mid-December, and as a result, it rises high enough above the horizon only a few hours after sundown, and remains high for the rest of the night. This means you can see the shower at a reasonably convenient hour – any time after about 9 P.M. local time.
The Geminids are active from December 7 through the 18th and peak very quickly on the night of December 13-14, Thursday night to Friday morning. Most activity occurs after midnight on the 14th, when as many as one hundred slow, graceful Geminids might be seen per hour under ideal conditions. They are bright, yellow meteors, the average magnitude being reported around +2.5.
Geminids are unique in that their parent body is not a comet, but an asteroid. This asteroid (probably a defunct comet), which has an orbital period of 1.43 years, was discovered in 1983 and was named Phaethon. It is only about three miles in diameter, but at perihelion moves to within about 13 million miles of the Sun – closer than the orbit of Mercury – though at aphelion it recedes to almost 220 million miles, beyond the orbit of the Earth.
For most observers at mid- northern latitudes, observing the Geminids requires a small dose of courage in order to face the freezing winter nights. Be sure to bundle up to keep the cold at bay, and bring a thermos of hot coffee, tea, or chocolate. You may also want to head inside every hour or so to warm up, but do not turn on any lights or you will ruin your dark adaptation.
- Geminid meteors appear to stream out of the constellation Gemini, from a single point called the radiant. Use this sky map to locate its position.
- The meteor shower is active from December 7 until December 18.
- The night of December 13-14 (Thursday night to Friday morning) is the best time to watch.
- The source of the Geminid shower is an asteroid named 3200 Phaethon.