Geminid Meteors Arrive Thursday Night
by Joe Rao on
What’s the best annual meteor display? Many experienced skywatchers would say it’s the Geminids of December rather than the better-known Perseids of August. And this month the “Gems” ought to be as good as ever. Especially with the Moon at new phase, there will be no moonlight to interfere so observing conditions will be perfect!
The shower is due to peak during the overnight hours of Thursday, December 13 into the early hours of Friday, December 14 for North America. It shows substantial activity for about one or two days before maximum and one day after maximum, with the post-maximum part of the shower displaying meteors that tend to be especially bright. As many as 60 to 120 “Gems” might be seen under “ideal” conditions: a wide-open view of a dark sky, far away from any light pollution. Conversely, expect to see less if your observing site is compromised by (for example) obstructions such as tall buildings or trees and/or streetlights or perhaps your next-door neighbor’s security light. Simply put: a city dweller will only see a fraction of the meteors that a person situated in a rural location will see.
I've been watching the Geminids for over 40-years and they are distinctly different from the much faster Leonid or Perseid meteors. In the case of those showers, you'll usually see a streak lasting for at most a second or so; blink and you might even miss it! But the Geminids move across your line of sight at a somewhat slower pace; my own analogy is that they seem to scurry from one part of the sky to another like field mice. Sky & Telescope magazine has often described them as “slow and graceful.” Many observers have described them as yellower than the meteors of other showers. Another thing that sets the Geminids apart are that although many of them are unusually bright, few leave persistent trains – lingering incandescent trails that may last several seconds or more. In fact, statistically, only two to four percent of the Geminids leave visible trains. In sharp contrast, usually about half of the meteors belonging to the Perseids or Leonids do so.
One thing that makes the Geminids special is that unlike many of the other meteor displays, you don't have to wait until the early hours of the morning. A productive Geminid watch can begin as early as 10 p.m. because the shower’s radiant—that point in the sky where the meteors appear to fan out from—is already halfway up in the east-northeast sky. In this case, the radiant is near the bright star Castor, one of the “Twin Stars” of the constellation Gemini (hence the term, “Geminids”). The higher a shower’s radiant, the more meteors flash into view all over the sky. Most showers’ radiants are highest just before dawn. But in the case of the Geminids, if you stay out until about 2 a.m. the radiant will be almost directly overhead. That’s when they’ll be most plentiful.
Over the years, the cold weather, no doubt, has worked against the Geminids becoming better known. Watching for meteors means holding still for long periods of time in a lawn chair, whereas most people outdoors in the winter are at least slightly active and generate more body heat. Meteor watching takes place in the coldest hours of the late-night. And you have to do it under a wide-open clear sky, which guarantees that radiational cooling will deepen the chill.
So be sure to bundle all parts of yourself evenly from head to feet, paying special attention to air leaks around the face, neck, wrists, waist, and ankles. Heavy blankets, sleeping bags, groundcloths, auto cushions and pillows are essential equipment. It helps to have had a late afternoon nap, a shower, and to wear all fresh clothing. Eating and exercising beforehand will increase your heat production.
A final note: You needn’t worry about getting hit by a Geminid meteor; they are tiny bits of cosmic dust and grit and all are consumed by way of friction in our upper atmosphere dozens of miles above our heads. In case of the Geminids, the only “danger” is getting coated by frost and falling asleep.
Good luck and clear starry skies to all!