The 2006 Geminid Meteor Shower

Dec 13, 2006
The 2006 Geminid Meteor Shower
Geminid meteors photographed in Dec. 2004 by Jason A.C. Brock of Roundtimber, Texas. Credit: NASA

The best meteor shower of the year peaks this week on Dec. 13th and 14th.

"It's the Geminid meteor shower," says Bill Cooke of NASA's Meteoroid Environment Office in Huntsville, Alabama. "Start watching on Wednesday evening, Dec. 13th, around 9 p.m. local time," he advises. "The display will start small but grow in intensity as the night wears on. By Thursday morning, Dec. 14th, people in dark, rural areas could see one or two meteors every minute."

The source of the Geminids is a mysterious object named 3200 Phaethon. "No one can decide what it is," says Cooke.

The mystery, properly told, begins in the 19th century: Before the mid-1800s there were no Geminids, or at least not enough to attract attention. The first Geminids appeared suddenly in 1862, surprising onlookers who saw dozens of meteors shoot out of the constellation Gemini. (That's how the shower gets its name, the Geminids.)

Astronomers immediately began looking for a comet. Meteor showers result from debris that boils off a comet when it passes close to the Sun. When Earth passes through the debris, we see a meteor shower.

For more than a hundred years astronomers searched in vain for the parent comet. Finally, in 1983, NASA's Infra-Red Astronomy Satellite (IRAS) spotted something. It was several kilometers wide and moved in about the same orbit as the Geminid meteoroids. Scientists named it 3200 Phaethon.

Just one problem: Meteor showers are supposed to come from comets, but 3200 Phaethon seems to be an asteroid. It is rocky (not icy, like a comet) and has no obvious tail. Officially, 3200 Phaethon is catalogued as a "PHA"—a potentially hazardous asteroid whose path misses Earth's orbit by only 2 million miles.

If 3200 Phaethon is truly an asteroid, with no tail, how did it produce the Geminids? "Maybe it bumped up against another asteroid," offers Cooke. "A collision could have created a cloud of dust and rock that follows Phaethon around in its orbit."

This jibes with studies of Geminid fireballs. Some astronomers have studied the brightest Geminid meteors and concluded that the underlying debris must be rocky. Density estimates range from 1 to 3 g/cm3. That's much denser than flakes of comet dust (0.3 g/cm3), but close to the density of rock (3 g/cm3).

So, are the Geminids an "asteroid shower"?

Cooke isn't convinced. 3200 Phaethon might be a comet after all--"an extinct comet," he says. The object's orbit carries it even closer to the Sun than Mercury. Extreme solar heat could've boiled away all of Phaethon's ice long ago, leaving behind this rocky skeleton "that merely looks like an asteroid."

In short, no one knows. It's a mystery to savor under the stars—the shooting stars—this Thursday morning.

A note about time: All times in this story are local to the reader. So "Thursday morning" means Thursday morning wherever you happen to live.

Source: by Dr. Tony Phillips, Science@NASA

Explore further: Is the universe finite or infinite?

add to favorites email to friend print save as pdf

Related Stories

The "magic hour" for Geminid meteors

Dec 13, 2013

As arctic air and record cold sweeps across the USA, amateur astronomers are looking at their calendars with a degree of trepidation. A date is circled: Dec. 14th. And below it says: "Wake up at 4 AM for the ...

Phaethon confirmed as rock comet by STEREO vision

Sep 10, 2013

The Sun-grazing asteroid, Phaethon, has betrayed its true nature by showing a comet-like tail of dust particles blown backwards by radiation pressure from the Sun. Unlike a comet, however, Phaethon's tail ...

Geminid meteors set to light up winter sky

Dec 13, 2012

(Phys.org)—On the evening of 13 and the morning of 14 December, skywatchers across the world will be looking up as the Geminid meteor shower reaches its peak, in potentially one of the best night sky events ...

The 2011 Geminid meteor shower

Dec 13, 2011

The 2011 Geminid meteor shower peaks on the night of Dec. 13-14, and despite the glare of a nearly-full Moon, it might be a good show.

Recommended for you

Is the universe finite or infinite?

Mar 27, 2015

Two possiblities exist: either the Universe is finite and has a size, or it's infinite and goes on forever. Both possibilities have mind-bending implications.

'Teapot' nova begins to wane

Mar 27, 2015

A star, or nova, has appeared in the constellation of Sagittarius and, even though it is now waning, it is still bright enough to be visible in the sky over Perth through binoculars or a telescope.

Dark matter is darker than once thought

Mar 27, 2015

This panel of images represents a study of 72 colliding galaxy clusters conducted by a team of astronomers using NASA's Chandra X-ray Observatory and Hubble Space Telescope. The research sets new limits on ...

Galaxy clusters collide—dark matter still a mystery

Mar 26, 2015

When galaxy clusters collide, their dark matters pass through each other, with very little interaction. Deepening the mystery, a study by scientists at EPFL and the University of Edinburgh challenges the ...

Using 19th century technology to time travel to the stars

Mar 26, 2015

In the late 19th century, astronomers developed the technique of capturing telescopic images of stars and galaxies on glass photographic plates. This allowed them to study the night sky in detail. Over 500,000 ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.