Geminid Meteor Shower

A Geminid meteor cuts across star trails over Arizona's Meteor Crater in a long-exposure picture.

A holiday light show is on offer for sky-watchers this week, as the annual Geminid meteor shower peaks during the overnight hours of December 13 and 14.

This year's Geminid shower should be filled with colorful shooting stars and fireballs—but catching the spectacle will be a matter of timing.  The best times are probably before the moon rises when it will be completely dark.  Once the moon is up its light will drown out fainter meteors.

Little Star of Sweden:  A Geminid meteor bursts above a thousand-year-old Viking church in Vallentuna, Sweden.

If you're out under clear skies, face northeast and look for meteors racing out from the shower's radiant constellation, Gemini, which will be low on the horizon.

The other best chance will be in the very early morning of December 14 when the shower's radiant will be very high overhead.  At that point face west -- away from the moon -- and look for meteors streaking down from the sky.

California Stars:  Seen from southern California's Anza-Borrego Desert, a flurry of meteors dart around the well-known Big Dipper star formation.

The Geminids peak will feature rates of up to 30 to 40 meteors an hour as seen from suburban locations and up to 100 meteors an hour from the dark countryside.

Despite the number of meteors likely visible, the Geminids don't usually get as much attention as the August Perseids, perhaps because the December shower falls close to the holiday season and during frosty weather in the Northern Hemisphere, where most of the shooting stars will be visible.

Valley of Fire:  A lone Geminid meteor appears to plummet in front of a rock formation in the Valley of Fire State Park in Nevada.

Meteor observing requires patience.  Recline and look skyward for the best chance of viewing some of the meteor shower.

Slow-Moving Geminids Easy to Spot

While the shower's peak will last only a few hours each night, dozens of shooting stars will be visible over the entire week. 

Geminid meteors are fairly slow travelers, moving less than half the speeds of meteors in other showers.

Orange Flash:  A shooting star brightens orange-tinted skies above Iran's Zagros Mountains.

Despite the glare of the waning moon, the Geminids may have a few surprises  for observers.

The Geminids have a good reputation for producing fireballs which are much brighter than average meteors and occasionally explode (see Major Green Meteor Lights Midwest Night Sky).

The Geminids can also be quite colorful compared with other showers, with some yellow and even occasionally red, green, and blue streaks.

Meteors Come From Mystery Object

Meteors are mostly sand grain-sized particles that enter Earth's atmosphere at high speed, burning up and superheating the air around them, which creates the characteristic short-lived streaks of light.

Shooting stars from the Geminid meteor shower zip across the night sky above the Zagros Mountains, yesterday.

Most annual showers occur when Earth passes through clouds of debris left behind by passing comets, causing tons of cosmic dust to rain down on the planet in short periods of time.

The Geminids are unusual, though, because they're thought to be the only annual meteor shower created by a mysterious asteroid-like object named 3200 Phaethon.

Discoverd in 1983 by a NASA satellite, Phaethon is roughly three-mile-wide (5 km.) space rock.  Its year-and-a-half-long orbit precisely matches the appearance of the Geminids, making the body a prime candidate for the source of the meteors.

Star Reserve:  Star trails streak over Lake Tekapo in New Zealand in a long-exposure picture.  The lake was one of the first sites designated as a Starlight Reserve as part of a UN-supported initiative to preserve the quality of the night sky and its cultural, scientific, or natural value.

Unlike icy comets, Phaethon doesn't release gases or produce a visible tail of debris as it nears the sun.  However, it is possible that is because the object has been thoroughly baked by its frequent passages close to our star's intense heat.

Fairly recently, astronomers detected anomalous brightening of Phaethon whenever it approached the sun, which suggests that the space rock might be releasing small caches of frozen gases that had been trapped within the asteroid.

Although 3200 Phaethon is widely considered to be an asteroid, it might in fact be better to classify it as a nearly dead comet.