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: Thermonuclear X-ray bursts on neutron stars set speed record

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

How can we find tiny particles in exoplanet atmospheres?

20 hours ago

It may seem like magic, but astronomers have worked out a scheme that will allow them to detect and measure particles ten times smaller than the width of a human hair, even at many light-years distance.  ...

Spitzer telescope witnesses asteroid smashup

Aug 28, 2014

(Phys.org) —NASA's Spitzer Space Telescope has spotted an eruption of dust around a young star, possibly the result of a smashup between large asteroids. This type of collision can eventually lead to the ...

Witnessing the early growth of a giant

Aug 27, 2014

Astronomers have uncovered for the first time the earliest stages of a massive galaxy forming in the young Universe. The discovery was made possible through combining observations from the NASA/ESA Hubble ...

User comments : 0