BLOOMINGTON - Don't expect spectacular fireworks when the Leonid meteor shower peaks overnight Saturday. This year's shower is classified as "weak."

Astronomers say the annual November occurrence is being upstaged by the arrival of a mysterious comet that shares the same last name as the fictional detective, Sherlock Holmes. The comet is visible to the naked eye at night even in towns where light pollution will block the Leonids.

Explaining the comet's odd appearance isn't so elementary, astronomers say. Other comets brighten gradually as they near the sun. But, Comet Holmes quickly flared up recently. It did the same thing the last time it approached Earth in 1892.

"Because of its unique behavior, it (Comet Holmes) is a once-in-a-lifetime thing," said Thomas Willmitch, director of the Illinois State University Planetarium. "This is a comet that likes to surprise people. We've never seen a comet so unexpectedly brighten as this one has. It was not expected to do this, and no one knows how long it will continue. This definitely has been a unique event. This is the biggie."

Comets are the mothers of meteor showers, which occur when the Earth passes through bits of dust and metal that comets leave behind. Like bugs hitting a windshield, pieces of debris heat up and streak across the sky as the Earth's atmosphere hits them.

The Leonid shower occurs when the Earth strikes the tail of Comet Tempel-Tuttle. The intensity of the resulting meteor shower depends on the density of the debris at the point the Earth passes through the tail and the length of time since the comet's last flyby.

The Leonid shower was so intense in 1833 that the night sky was ablaze with 200,000 shooting stars every hour. People awoke from their sleep afraid. The last time the comet passed was 1999, and its dust is dissipating, Willmitch said. This time, comet forecasters believe the shower at its peak will add just 10 to 15 meteors an hour, or about one every six minutes, to the eight meteors that occur every hour on a routine night.

"Then again, surprises are always possible with the Leonids," Willmitch said.

Michael Rogers, vice president of Twin City Astronomers, is hoping for a real show. When meteors come slowly, he's usually looking the other direction when someone shouts, "Did you see that? Did you see that?"

"Two hundred thousand an hour; that must have been unbelievable," Rogers said. "It would have looked like the sky was exploding. I'd like to see a storm like that. No matter where I look, I would see something."

The Leonids - so named because the meteors appear to originate from the constellation Leo the Lion - will be most visible to people in rural areas after midnight Saturday. Town lights will block them. To find Leo, form a straight line from the two stars in the cup of the Big Dipper. Follow the line out of the bottom of the cup east across the sky to the bright star named Regulus low on the horizon. Regulus is the "period" at the bottom of a backward question mark, which is Leo.

To find Comet Holmes, look northeast to the "W"-looking Cassiopeia constellation. Then, look right below it to Perseus, which resembles the stick figure of a person with two distinct legs bent at the waist to the right. The fuzzy object at the waist is the comet. It will be very close to a bright star. Binoculars or a telescope will help to see detail.

On the Net

http://www.skyandtelescope.com

Sky viewing tips

• Get as far from city lights as possible

• Moonlight interferes. Go after midnight.

• Be patient when viewing the Leonid shower. Expect just one meteor every six minutes.

• Visit www.skyandtelescope.com for directions on where to look.

• Check out http://leonid.arc.nasa.gov/estimator for a graph on when peak meteor activity will occur.