Heavenly half-storm nears
Meteor showerLeonids expected to make strong display next week

By Wayne Harris-Wyrick Comments 0
Published: November 3, 2009

This year has been a bit of a bust for meteor showers. For the normally good Perseids, back in August, a third-quarter moon hindered a mediocre shower. But what could prove to be the best meteor shower of the year comes Nov. 17 with the Leonid meteor shower.

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Meteor showers occur when Earth passes through the debris baked off a comet. Comets are dirty iceballs 10 miles across or so. When a comet comes into the inner solar system, the sun’s tremendous heat vaporizes the surface layer of the comet, releasing any trapped dust and rock chunks.

When that debris trail slams into Earth’s atmosphere, it creates a meteor shower. Earth reaches the same spot in its orbit on the same day each year, so meteor showers are annual events.

Some readers may remember the Leonid meteor storms in 1999 and 2001. A meteor storm is defined as 1,000 or more meteors per hour.

"On Nov. 17, we expect the Leonids to produce upward of 500 meteors per hour,” says Bill Cooke of the NASA Marshall Space Flight Center. "That’s a very strong display.”

That would make the 2009 Leonids a half-storm, like what occurred in 1998. But there is a difference between this year’s Leonid shower and 1998’s. That half-storm occurred when Earth passed through a stream of particles released from the parent comet Tempel-Tuttle in 1333, and it was rich in nugget-size pieces, which create dramatic fireballs. This year’s predicted half-storm comes from a debris trail released by the comet in 1466 and seems to be mostly dust-size particles with few nuggets. Lots of meteors, but few bright fireballs.

The bad news: The peak occurs in midafternoon for us. By the time the sun sets that evening, we likely won’t get 500 per hour, but we may still see a decent meteor shower of 100 to 200 per hour. "I hope so,” Cooke said. "It’s a long way to Mongolia.”

The good news: no moon in the sky to interfere with the show.

Astronomy notes

→Learn about meteor showers and other upcoming astronomical phenomena in the Kirkpatrick Planetarium’s main feature, "Tonight’s Sky,” which runs daily. Call 602-3761 for information or go online to www.science museumok.org.

→The Oklahoma City Astronomy Club meets at 6:45 p.m. Nov. 13. Guests are welcome. For more information, go online to the club’s Web site, www.okc astroclub.com.

→Planet visibility report: Jupiter is high in the south at sunset and sets in the west around midnight. Mars rises about 10 p.m., and Saturn follows about 2 a.m. Mercury and Venus are lost in the sun’s glare. Full moon occurred Nov. 2, with new moon coming Nov. 16, a day before the Leonid Meteor half-storm.

Wayne Harris-Wyrick is director of the Kirkpatrick Planetarium at Science Museum Oklahoma. Questions or comments may be e-mailed to wwyrick@sciencemuseumok.org.