The Geminids are the most reliable meteor shower of the year because it is an old shower and the therefore the individual meteors are evenly distributed throughout the meteor stream. The particles that enter our atmosphere are the remnants of a defunct comet, now identified as asteroid 3200 Phaethon. The radiant point in Gemini, near the stars Castor and Pollux, is well above the eastern horizon at 10:00 pm, allowing us to begin observing before midnight. As the night progresses and Gemini rises higher into the sky, the number of meteors seen should increase.
Because the Earth intercepts the stream of particles at a right angle, the meteors hit our atmosphere at a moderate speed of 21.75 miles per second. In a dark sky an observer should expect to see about 75 meteors per hour, though there is potential to observe perhaps two shooting stars per minute (110 to 130 per hour). The Geminids are characterized by their multi-colored display (65% being white, 26% yellow, and the remaining 9% blue, red and green). They are fairly bright and also have a reputation for producing exploding meteors called fireballs.
In addition, the Geminid shower also now sports two different peaks about six hours apart. An observer may therefore possibly see several increases and decreases in the number of meteors during the course of the night. Whether or not we see both those peaks entirely depends upon the time the Earth intercepts the meteor stream and its tributaries.
You’ll know you’ve seen a Geminid if you can trace the path of the meteor trail back to the radiant point in Gemini. However, you also do not want to stare directly at Gemini. Seldom does a meteor begin right at that point in the sky. An observer needs to scan as much of the sky as possible, constantly shifting your gaze high and low, right and left.