Christmas lights are not the only splashy displays brightening our winter nights. The Geminids, an annual meteor shower, will streak across the heavens in mid December in a light show that promises to be as captivating as store-bought twinklers.
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Named Geminids because they appear to radiate from the constellation Gemini, this is one of the best meteor showers of the year and rarely disappoints. To skywatchers, meteors look like flares from Fourth of July fireworks as they arc across the heavens (hence the name shooting stars or falling stars). But that flash of light is actually from the grit and debris in a dead comet's orbital path. When Earth intersects a comet's orbit, it gets hit by swarm of these fast-moving particles, most of them smaller than a grain of sand. The Geminid particles hit Earth's atmosphere at 22 miles per second, heat up to incandescence, and create a yellowish-white streak of light.
"It's a complicated atomic process," says Stephen Maran, author of Astronomy for Dummies, who describes the action as "energizing and exciting air molecules as the particles go by" to create trails of glowing light.
The Geminids shower cranks up on December 7 and stays around until December 17. The meteors start out at a rate of 10 to 15 an hour. By their peak, on December 14, with optimal conditions of a clear dark night as many as 120 to 180 per hour will whiz across the sky. Then they begin to taper off, diminishing in frequency over the next several days.
A patient skywatcher might observe a shooting star on almost any given night, but not nearly as many as one sees during the Geminids, says Robert Bruce Thompson, author of Illustrated Guide to Astronomical Wonders. "In four hours, you might see a dozen," he says. "The meteors are up there, but they're too dim to be noticed." It's the "concentration" that makes the Geminids so spectacular.
"The smallest meteor particles are hitting the Earth all the time," Maran explains. "There are some in your hair right now, but they're microscopic and can't be seen with the naked eye."
Lucky observers might occasionally see a fireball—a pea-to walnut-size chunk of comet dust that becomes a stunningly bright meteor. "Fireballs are rare," says Thompson. "One the size of a large pebble can light up the entire landscape."
Observers all over the world will have an opportunity to see the Geminids. The very best vantage points, however, will be in East Asia—China, Japan and nearby mid-northern latitude countries. The Geminids hours of maximum activity occur when it's nighttime in those regions. That translates to about noon Eastern Standard Time in the United States. Visibility is obscured when the sun is high, but as darkness falls there are plenty of places around the United States to catch the show.
Here are some tips to get the best view of the Geminids:
- The darker the location, the more you're going to see. Head 15 to 20 miles out of town, away from city lights and smog. Pick a high altitude location that has you looking away from the city.
- Turn off white light sources or cover them with red cellophane. Vehicle headlights, cell phones, computer screens, even flashlights are sources of light pollution.
- Leave telescopes and binoculars at home when viewing the Geminids. The high-powered devices will actually limit your viewing because you may be focused on one part of the sky when the meteors streak across another.
- Get horizontal and comfortable. Stretch out on a lawn chaise lounge or a sleeping bag for a good peripheral view of the sky.
- Bundle up. The December air can be quite cold when you're sedentary. Dress as if the temperature were 30 degrees colder.
- Plan to stay up. The best viewing is after the moon has set, between midnight and just before dawn, but you'll see some meteors by 10 p.m EST.
- Be patient.
- Contact your local amateur astronomy club for information about skywatching in your area.