To just about everyone’s mind, the most famous meteor shower of all is the Perseids of August. Actually, however, the Geminids of December consistently offers more “shooting stars” than any other display—typically at least 100 per hour, and occasionally as many as 120 or two meteors per minute at its peak! But alas, apparently the cold nights of winter keep many people indoors, relegating this great display of celestial fireworks to undeserved obscurity.
Watching shooting stars is so much fun for the casual stargazer! It requires no optical aid at all—just a clear night with little or no moonlight to interfere with visibility and a good view of the sky overhead. Nothing is as thrilling as the sudden appearance out of the darkness of a bright meteor with its trail of debris as it burns up in the atmosphere. This year’s Geminid Meteor Shower will be at peak activity on the late evening of December 13th into the morning of the 14th. The Moon this time will be present as a fat crescent, brightening the sky to some extent (but not enough to spoil the fun) until it sets about midnight. The best time to begin observing the display will be around 10 p.m. on the 13th and continuing into the morning hours. The meteors will appear to radiate from near Castor, one of the two bright “Twin Stars” (the other being Pollux) marking Gemini. To find them, set your Scientifics Star and Planet Locator for about 10 p.m. and face east, where you’ll see the pair about halfway up the sky.
This early rising of the radiant helps make the Geminids so special to sky watchers: those of most showers lie below the horizon during the evening hours. But in this case, it’s already well up and you’ll see meteors streaming outward from it, with their numbers steadily increasing as the night grows later and Gemini climbs ever-higher. BTW—it’s actually the horizon “setting” as the Earth spins ever-eastward at over 900 mph (depending on your latitude) rather than celestial objects themselves rising. This is most striking in the case of the Sun and Moon, as they dramatically seem to pop-up into the sky from out of nowhere!)
There’s a subtle but fascinating reason why meteor showers increase in activity towards dawn. During the evening hours, we’re on the side of our planet “facing away” from the direction the meteors are approaching, so they essentially 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. This results in many more meteors being seen right up until the dawn twilight interferes, which is when the impact-effect is at its maximum. Their higher velocity also makes those that are seen in the morning hours brighter than in the evening.
— James Mullaney
Former assistant editor at Sky & Telescope magazine & author of 10 books on stargazing. His latest, Celebrating the Universe!, is available from HayHouse.com.