Photograph by Wally Pacholka, TWAN
for National Geographic News
December 13, 2009
Late tonight is the peak of the year's most prolific annual cosmic fireworks show—the Geminid meteor shower (Geminids picture).
The meteor shower has been growing in intensity in recent decades and should be an even better holiday treat than usual this year, since it's falling in a nearly moonless week.
Coming fast on the heels of its more famous cousin the Leonid meteor shower—which peaked less than a month ago—the Geminid show should feature as many as 140 shooting stars per hour between Sunday evening and Monday morning.
The Geminids are slow meteors that create beautiful long arcs across the sky—many lasting a second or two.
Favoring observers in the Northern Hemisphere, the Geminids are expected to be most frequent within two hours of 1:10 a.m. ET in the wee hours of Monday.
The shower's radiant—the point in the sky from which the meteors appear to originate—is the constellation Gemini, which rises above the eastern horizon after 9 p.m. local time.
Astronomers recommend observers head outside between 10 p.m. and 5 a.m. local time.
As with any meteor shower, the Geminids will be muted in light-polluted cities, but even suburban sky-watchers may catch as many as 60 meteors per hour during peak time.
Geminid Meteor Shower: Rising Star
The Geminids have been historically overlooked, simply because of their timing so close to the busy holiday season and during frigid winter nights, astronomers say.
But that's beginning to change, thanks to the Geminids' rising intensity over the past few decades.
In fact, for many astronomers, the December meteors have now dethroned the more popular August Perseid meteor shower as the shooting star event of the year.
"It may come as a surprise to many, but the Geminids are currently richer and are brighter on average," said Anthony Cook, astronomy observer at Griffith Observatory in Los Angeles, California.
Why the sudden illumination?
Earth is plowing deeper every year into an ancient stream of rocky debris left behind by a mysterious 3.1-mile-wide (5-kilometer-wide) object that orbits the inner solar system, he said.
When Earth's atmosphere crosses paths with that debris cloud, the rocks are superheated and burn out—and new Geminids are born.
Geminids' Mystery Parent
The Geminid meteors all appear to be chips off a mysterious rocky object called 3200 Phaethon.
Other meteor showers come from material shed by melting comets—which are massive chunks of dirty ice and rock—as they pass close to the sun. (See asteroid and comet pictures.)
But no one knows for sure whether the Geminids' parent object, first identified in 1983, is an asteroid or the core of an ancient comet that simply sputtered out.
Recent observations of Phaethon, though, suggest it's a nearly dormant comet, and the Geminids' parent is now officially classified as such by NASA.
The research revealed that Phaethon is the rocky skeleton of a comet that lost its ice after too many close encounters with the sun, according to NASA.
The shooting stars' rocky, hard exterior—as well as the fact that they, unprotected by ice, get baked by the sun—may help explain why Geminids are slower and last longer in the sky than other shooting stars, said Peter Brown, a meteor expert at the University of Western Ontario in Canada.
"They have the ability to penetrate deeper into Earth's atmosphere," Brown said, "and burn up at much lower altitudes than meteors associated with the Perseids and Leonids."
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