Leonids light up night sky
By Richard Stenger
CNN
(CNN) -- One of the most celebrated meteor showers peaked early Tuesday, sending hundreds or thousands of fireballs streaking through the atmosphere each hour.
The annual Leonids meteor shower takes place every November when the Earth passes through a debris trail left by a comet that sheds material as it swings near the sun every 33 years.
This year, our planet plowed through two clouds of debris from Comet Temple-Tuttle, providing peak periods some six hours apart overnight between November 18 and 19.
Astronomers predicted that viewers in Europe and North America might see several thousands of meteors per hour. But a full moon, fog and clouds diminished the show for many viewers on both continents.
The tiny fragments, often no bigger than sand grains, heat up and vaporize as they bounce across the upper atmosphere at speeds of about 160,000 mph (260,000 km/h).
The meteor concentration varies sporadically from year to year, depending on whether the Earth smacks into sparse or thick bands of the comet's debris.
During the 2001 show, observers saw up to 10,000 meteors an hour, the heaviest concentration of Leonids since 1966, when there were an estimated 150,000 shooting stars an hour during peak times.
The Leonids are so named because they seem to originate from the constellation Leo, otherwise known as the Lion.
