November 10, 2009 by Dr. Tony Phillips

This year's Leonid meteor shower peaks on Tuesday, Nov. 17th. If forecasters are correct, the shower should produce a mild but pretty sprinkling of meteors over North America followed by a more intense outburst over Asia. The phase of the Moon will be new, setting the stage for what could be one of the best Leonid showers in years.

"We're predicting 20 to 30 meteors per hour over the Americas, and as many as 200 to 300 per hour over Asia," says Bill Cooke of NASA's Meteoroid Environment Office. "Our forecast is in good accord with independent theoretical work by other astronomers."

Leonids are bits of debris from Comet Tempel-Tuttle. Every 33 years the comet visits the inner solar system and leaves a stream of dusty debris in its wake. Many of these streams have drifted across the November portion of Earth's orbit. Whenever we hit one, meteors come flying out of the constellation Leo.

"We can predict when Earth will cross a debris stream with pretty good accuracy," says Cooke. "The intensity of the display is less certain, though, because we don't know how much debris is in each stream." Caveat observer!

The first stream crossing on Nov. 17th comes around 0900 UT (4 a.m. EST, 1 a.m. PST). The debris is a diffuse mix of particles from several old streams that should produce a gentle display of two to three dozen meteors per hour over North America. Dark skies are recommended for full effect.

"A remarkable feature of this year's shower is that Leonids will appear to be shooting almost directly out of the planet Mars," notes Cooke.

It's just a coincidence. This year, Mars happens to be passing by the Leonid radiant at the time of the shower. The Red Planet is almost twice as bright as a first magnitude star, so it makes an eye-catching companion for the Leonids.

The next stream crossing straddles the hour 2100-2200 UT, shortly before dawn in Indonesia and China. At that time, Earth will pass through a pair of streams laid down by Comet Tempel-Tuttle in 1466 and 1533 AD. The double crossing could yield as many as 300 Leonids per hour.

"Even if rates are only half that number, it would still be one of the best showers of the year," says Cooke.

The Leonids are famous for storming, most recently in 1999-2002 when deep crossings of Tempel-Tuttle's debris streams produced outbursts of more than 1000 meteors per hour. The Leonids of 2009 won't be like that, but it only takes one bright Leonid streaking past Mars to make the night worthwhile.

Enjoy the show.

Source: Science@NASA, by Dr. Tony Phillips

Thanks to Paulette for sending the details.

Celestial Spectacle over City Next Week—by George Skaria

Here is a news item from Sakaal Times 11 November 2009 of Pune Maharashtra India:

A celestial spectacle is round the corner: The Leonid meteor shower on the night between November 17 and 18. Sky-gazers are expecting a semi-storm, a real splash of meteors touching in excess of 500 per hour.

“Debris left by Comet Temple Tuttle will literary sparkle the Pune skies on a moonless night,” Jyotirvidya Parisanstha’s (JVP) Deepak Joshee told Sakaal Times. JVP is all geared up to record and experience the celestial spectacle, he said.

“There are many comets in the sky and many a time these comets leave some debris, which revolves round the sun in the same orbit. However, there is one special comet, Temple Tuttle, that is interfaced to earth and the orbit revolving around the Sun,” Joshee said.

Temple Tuttle visits the solar system every 33 years and it keeps on leaving behind debris in the orbit. As a result, each year during mid-November, the Earth passes through the debris and one could witness large number of meteors falling on the Earth in the form of Leonid meteor. Although the comet orbits around the Sun, the debris moves at a huge speed of 78 km per second and when the earth collides with the object it penetrates into the atmosphere.

Due to the high velocity, large amount of friction is created when the debris hits the atmosphere. This movement leads to a trail of lights moving in the sky as the meteors shower, Joshee added.

"This year everything seems to be in place for a semi-storm, meaning meteors in the excess of 500 per hour. The peak is expected at 3.20 am, which means Leonid will be well above the horizon on a moonless night,” he said.

Puneites have been enjoying this event since 1998, when the there were more than 1,000 meteors. "For the last few years, the intensity was diminishing since we had daytime in India during the peak. So we missed this spectacle," said Joshee.