A Geminid meteor streaks over Joshua Tree National Park in 2010. (Photo: Henry Lee/Flickr)
The world probably won't end this month, despite a widespread Mayan apocalypse myth, but that doesn't necessarily mean the sky won't fall. In fact, many experts predict the heavens will begin raining down fireballs as early as this week.
Those fireballs, of course, are part of the annual Geminid meteor shower, and virtually all will burn up in the atmosphere. That may disappoint doomsayers, but it's great news for skygazers. Not only are the Geminids among the year's most reliable and bountiful meteor showers, but they should be especially visible this year thanks to the waning moon, which will go dark just as they reach their peak Dec. 13 and 14.
The yearly Geminid barrage officially starts this week, and should continue through Dec. 17. It'll be fairly sparse at either end of that window, but after midnight Dec. 13, people under dark, clear skies may see anywhere from 80 to 120 meteors per hour. While moonlight has outshone many recent showers — including last year's Geminids — the so-called "grand finale" of 2012 is widely expected to impress.
"The Geminid shower is one of the most active of any year and usually produces a good percentage of bright meteors, so it's worth watching even under less-than-favorable conditions," says Richard Talcott, senior editor for Astronomy magazine, in a 2012 Geminid preview. "This year, however, conditions are excellent."
To generate some extra buzz about the Geminids' upcoming peak, the astronomy group Meteorwatch even produced this Hollywood-style trailer:
Geminids are relatively slow and bright compared with other meteors, and often leave smoke trails that can linger for several seconds. But their differences also run much deeper: Unlike most meteor showers, which occur as Earth passes through a comet's dusty debris trail, the Geminids' cosmic origin is shrouded in mystery.
They're relatively young for a meteor shower, with the first observations recorded in 1862, and astronomers spent more than a century searching for their parent comet. Finally, in 1983, NASA's IRAS satellite found a strange asteroid whose orbit takes it unusually close to the sun — and which seemed to be the long-sought source of the Geminids. Named "3200 Phaethon," this rocky object doesn't shed debris like a comet, and scientists still aren't sure exactly how it produces the meteor shower.
Aside from the Geminids, plus a few minor annual showers like the Sigma Hydrids, some NASA computer models also predict a brand new meteor shower this month. Starting next week, Earth may pass near a decades-old debris field from the comet Wirtanen, which was discovered in 1948 and takes 5.4 years to orbit the sun.
"In the most optimistic scenario," NASA reports, "viewers could see as many as 10-30 meteors per hour radiating from a point in the constellation Pisces in the early evenings, sometime between December 10 and 15." This coincides with the Geminids' peak, the agency adds, "so skywatchers have a chance of a 'meteor night' after sunset on December 13; meteors from the new shower (if any) will be visible in the early evening, with the Geminids making their appearance later on and lasting until dawn."
For the best chance to see this month's meteors, leave your predawn schedule open Dec. 13 and 14, and get as far away from light pollution as you can. Talcott suggests traveling 40 miles from a major city, but some urban and suburban areas can work if outdoor lighting is minimal. According to StarDate.org, your eyes are adequately "dark-adapted" if you can see each star in the Little Dipper constellation. EarthSky.org also notes it can take 20 minutes before human eyes fully adjust to the dark.
No binoculars or telescopes are needed to see meteors; they'll just limit your field of view. Patience is required, though, even for a prolific shower like the Geminids, so you may want to bring a chair or blanket to sit on. Feel free to warm up with a hot toddy, but be warned: "Alcohol interferes with the eyes' dark adaptation as well as the visual perception of events," Astronomy magazine points out.
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