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Science & Space

Leonid meteor shower to light up night sky

By Kate Tobin
CNN

Italian astrophotographer Lorenzo Lovato captured this Leonid fireball in 1998.
Italian astrophotographer Lorenzo Lovato captured this Leonid fireball in 1998.
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(CNN) -- The annual Leonid meteor shower is set to rain space dust over Earth for the next few days, putting on a show for night skygazers. Astronomers disagree as to when the shower will peak -- some say Wednesday, others Friday.

Every year at this time, Earth passes through the dusty debris trail of the comet Tempel-Tuttle. As the tiny meteors -- most no bigger than a grain of sand -- hit earth's atmosphere, they burn up in a fiery streak. They are also known as shooting stars.

It generally takes a couple of days for Earth to pass completely through the debris cloud, and it is hard to say exactly when the shower will peak. Scientists do not expect this year's shower to be particularly spectacular, with only 15 to 20 meteors per hour visible under optimal conditions. But exactly how intense the shower will be has been notoriously hard to predict accurately.

Comet Tempel-Tuttle orbits the sun once every 33 years. It last passed close to Earth in March 1998, laying down a fresh debris trail. As a consequence, astronomers predicted the 1998 and 1999 Leonid meteor showers could be spectacular. The 1998 event was a disappointment, with only about 250 meteors per hour observed at the shower's peak. But the 1999 Leonids met expectations, with the shower becoming a storm of nearly 4,000 meteors per hour over Europe and the Middle East.

Skywatchers who hope to catch the show should try to get out to an area where the sky is dark, away from city lights. While the Leonids are so-named because they appear to come from the area of the sky where the constellation Leo is found, the best way to view them is to find a place with a good unobstructed view of the whole sky. No telescopes or binoculars are necessary.

In those years when the shower reached "storm" proportions, meaning thousands of meteors per hour, the streaks of light filled the whole sky.

Obviously, cloudy weather could ruin the whole show.

While meteor showers may make for entertaining skygazing, the risk of getting hit by a meteorite is practically zero. The largest of the Leonid meteors -- a very small number -- might be the size of baseballs. But after striking the atmosphere at 44 miles per second, few if any will survive long enough to hit the ground.

Meteor showers do pose a slight risk to satellites in orbit. Even the ones the size of a grain of sand, because they are moving 200 time faster than a speeding bullet, could damage a satellite beyond repair if it were to hit it just right. Another danger from the impact of a meteor on a satellite is an effect called "charging" in which the collision creates a tiny cloud of electrically charged gas, called plasma, that can short out electrical systems.

Many satellite operators take precautions during meteor showers, such as angling sensitive optics away from the oncoming meteors, or turning solar arrays on edge to the shower.

However, NASA scientist Don Yeomans noted that the risk of a satellite getting "taken out" by a Leonid is quite small, less than 0.1 percent. He said satellites are more at risk every day from man-made space junk.


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