Geminid meteor shower returns December 13-14

December 10, 2014 by Alan M. Macrobert, Sky & Telescope, Sky & Telescope
The Geminid meteors can flash into view anywhere in the late-night sky. But if you follow their paths back far enough, they all appear to diverge from a point in the constellation Gemini. The meteors' perspective point of origin is called the shower's radiant. Don't expect to see several meteors at once! This diagram is meant only to show their divergence from the radiant point. Click on the image for a larger version. Credit: Sky & Telescope / Gregg Dindermann

If it's clear late on Saturday and Sunday nights (the nights of December 13th and 14th), keep a lookout high overhead for the "shooting stars" of the Geminid meteor shower. "The Geminids are usually one of the two best meteor showers of the year," says Alan MacRobert, senior editor at Sky & Telescope magazine. "They are sometimes more impressive than the better-known Perseids of August."

Under a clear, dark sky, you might see a shooting star every minute from 10 p.m. local time until dawn on the peak nights. If you live under the artificial skyglow of the numbers will be reduced, but the brightest meteors will still shine through. There will be some interference as well from a last-quarter Moon, which rises close to midnight.

Lower counts of Geminid meteors should be visible earlier on those evenings, and for a few nights before and after December 13th and 14th.

To watch for meteors, you need no equipment other than your eyes. Find a dark spot with an open view of the sky and no glaring lights nearby. Bundle up as warmly as you can in many layers. "Go out late in the evening, lie back in a reclining lawn chair, and gaze up into the stars," says MacRobert. "Relax, be patient, and let your eyes adapt to the darkness."

Geminids can appear anywhere in the sky, so the best direction to watch is wherever your sky is darkest, probably straight up. Small particles create tiny, quick streaks. Occasional brighter ones might sail across the heavens for several seconds and may leave a brief train of glowing smoke.

If you trace each meteor's direction of flight backward far enough across the sky, you'll find that this imaginary line crosses a spot in the constellation Gemini near the stars Castor and Pollux. Gemini is low in the eastern sky during late evening and climbs to high overhead in the hours after midnight (for skywatchers at north temperate latitudes). The special spot is called the shower's radiant. It's the perspective point from which all the Geminids would appear to come if you could see them approaching from far away, rather than just in the last second or so of their lives as they dive into Earth's upper atmosphere.

The Source of the Geminid Meteors

During the 2004 Geminid meteor shower, Alan Dyer caught a bright fireball with a tripod-mounted digital camera. He used a wide-field, 16-mm lens for a 1-minute exposure at f/2.8 with an ISO setting of 800. Expect to shoot a lot of frames before you get this lucky. Credit: Sky & Telescope / Alan Dyer

The Geminid meteors are created by tiny bits of rocky debris (the size of sand grains to peas) shed from a small asteroid named 3200 Phaethon, which was discovered in 1983. Before then no one knew the source of the Geminid shower. Phaethon is small, only about 3 miles across, and it loops around the Sun every 1.4 years in an orbit that approaches the Sun closer than any other known asteroid.

Over the centuries bits of Phaethon have spread all along the asteroid's orbit to form a sparse, moving "river of rubble" that Earth passes through in mid-December each year. The particles are traveling 22 miles per second (79,000 mph) with respect to Earth at the place in space where we encounter them. So when one of them dives into Earth's upper atmosphere, about 50 to 80 miles up, air friction vaporizes it in a quick, white-hot streak.

More about Light Pollution

Phaethon completes an orbit around the Sun every 1.4 years. Its path is highly elongated, much like a comet's. Perhaps it is an extinct comet, or maybe it's a true asteroid that is cracking and shedding rocky bits when closest to the Sun. Credit: Sky & Telescope diagram

Light pollution in the sky doesn't interfere just with meteor watching. It's the bane of everyone from backyard nature lovers to professional deep-space researchers. But most light pollution is unnecessary. It results from wasted light beamed uselessly sideways or upward from all of the poorly designed and improperly aimed outdoor lighting for many miles around.

This waste can be prevented by installing modern, fully shielded fixtures, and by aiming fixtures more downward toward the ground where the light is wanted. These simple steps not only reduce light pollution in the sky but allow great savings of electricity. "Be aware that some LED fixtures emit harsh, blue-hued light that makes it especially difficult to see the stars," notes S&T senior contributing editor Kelly Beatty. He recommends that you install LEDs with a "color temperature" (marked on the packaging) that's no greater than 3000K.

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2 comments

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Trezktv
not rated yet Dec 10, 2014
Hey folks, can we PLEASE stop using the imperial? I know most of your views come from americans and it is normal to want to cater to them, but SI units are the international standard for a reason, at least, AT LEAST add a small parenthesis with the measures on metric.
Vietvet
5 / 5 (1) Dec 13, 2014
Just stepped outside not thinking about the meteor shower and to the east-north-east saw a meteor that appeared traveling straight down. It was spectacular. Imagine holding a new pencil at arms length. That was the width and length of its path and it was a brilliant green before it disappeared with a white flash.

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