Geminids to Be Outshone by Big, Bright Moon

When it comes to sky shows, sometimes a lunar blessing can be a meteor’s curse.

Friday night’s biggest, baddest full moon is sure to capture the hearts of many a skywatcher. But it also means this year’s Geminid meteor shower, due to peak the night of December 13-14, will be largely washed out by the satellite’s shining face.

In recent years the Geminids have become the most active of the annual meteor showers, with peak rates of 110 “falling stars” an hour on record for 1996.

Last year’s shower fell during a moonless night, prompting predictions of the “year’s best” sky show for 2007.


A Geminid meteor as seen from San Francisco on December 14, 2007

—Photo courtesy Mila Zinkova

Not so for 2008. Astronomers predict that during this year’s shower only the brightest meteors will cut through the moon’s glare, and the folks over at EarthSky are even suggesting would-be skywatchers should skip the frigid December vigil and wait for a clearer view of the Quadrantid shower in early January.

Die-hard fans may get lucky, though, especially if you can get away from city lights and recline in the weekend chill.

The fun part about the Geminids, no matter how many you see, is knowing where they come from—a mystery object called 3200 Phaethon.

Most annual showers are caused by comets orbiting the sun. As they get close to the hot star, bits of their ice-rock bodies start falling off, creating those iconic tails.


—Image courtesy NASA

In some cases a comet’s tail sweeps over Earth, and the bits that come streaming through our atmosphere are what we see as meteors.

The cometary pieces are itteh-bitteh (often the size of sand grains), but they’re fast, buzzing in at several miles a second and giving folks a fabulous light show as they burn up high over Earth.

Since 1862 astronomers have known that the Geminids are an annual event, and in 1983 scientists finally found their source: an object in just the right orbit to match the seeming source-point of the shower (the constellation Gemini).

Then came the kicker—the object’s chemical signatures indicted it is an asteroid, not a comet.

But rock-filled asteroids shouldn’t break up as they near the sun, so why is this one sending us an annual sky show?

Studies of the meteors themselves suggest Phaethon is a sort of defunct comet that has gathered so much dust over time that it only looks like an asteroid on the outside.

But as far as we can see the body is missing a tail, so until we can land something on it or smash something into it, the mystery endures.

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