The Leonids are a tough nut this year, but that doesn’t mean you should give them the cold shoulder. While the shower returns every mid-November to toss 15 meteors per hour our way in the wee hours of the morning, this year’s full moon will halve that number. Still, they’re an enjoyable diversion. If you’re out looking for Comet ISON, keep an eye open for meteors shooting from inside the Sickle of Leo just above the star Regulus.
While fewer in number this year, the Leonids are famed for fireballs that leave bright, persistent “smoke trails” called trains. These are actually tubes of air molecules excited and ionized by the meteoroid’s passage that glow briefly as they return to their neutral or pre-excited states. Traveling at an average speed of 162,000 miles per hour (261,000 km/hr) it’s no wonder Leonids leave trains. They’re one of the fastest meteor streams around.
Comet 55P/Temple-Tuttle supplies the material that comprises the shower. Vaporizing dirty ice when the comet nears the sun leaves streams of dust particles in its wake. Every November, Earth’s path intersects that of the comet and we smack into dust and debris scattered along its orbit. Because the grit hits the upper atmosphere at high speed, it burns up in a flash of light called a meteor.
Every 33 years, Comet Temple-Tuttle returns to the vicinity of the sun, and if the Earth happens to be near the comet’s orbit at the time, we see a massive increase in the number of Leonids. Two of the greatest showers on record with rates of around 100,000 per hour occurred in 1833 and 1966. The 2001 shower wasn’t bad either. Many of you will still remember that one and the many fireballs that whizzed across the sky. Here at my place the whole family came out to look; it was one of the few times I’ve had willing company at 4 a.m.
You can start watching for Leonids anytime from around 1 a.m. till dawn, when the radiant or point in the sky from which the meteors will appear to originate, rises in the eastern sky. This year’s shower features two peaks, the first at 4 a.m. CST (10 UT) and a second burst at 10 a.m. CST or 6 a.m. Hawaiian Time. The earlier peak favors the eastern half of the U.S., Canada and South America; the second the central Pacific including Hawaii. But again, remember this is an off-year for the shower and numbers will probably be low.
Watching the shower is easy. Sit down in a reclining chair facing toward the south or southeast and kick back. While the Leonids are sparse except at those 33-year intervals, upticks and outbursts aren’t uncommon. In 2008 and 2009 the maximum hourly rate recorded by pro meteor observers reached the mid-70s, so who knows.
You can track the pulse of the Leonids during and after the shower by visiting the live ZHR graph on the International Meteor Organization’s (IMO) website. The ZHR or Zenithal Hourly Rate is the number of meteors a single observer would see under a clear, dark sky with the radiant high in the sky near the zenith.
Another cool way to stay in touch with the shower and see quickly-posted photos is to head over to the Meteorwatch website. You can also contribute your own meteor observations there via Twitter.
Good luck and dress warmly!