Around the world, astronomers and amateur stargazers headed for fields, beaches, deserts and mountaintops Wednesday to watch what could be the most spectacular meteor shower since 1966 and for decades to come.
The annual Leonid meteor shower was expected to reach its peak overnight Wednesday. However, predicting timing and intensity is an inexact science, and the quarter moon, the lights of civilization and cloud cover could obscure the view.
"It could be spectacular, or it could be a dud," said Williams College astronomer Jay Pasachoff, who picked a beach outside Valencia, Spain, for his viewing spot.
The best American viewing of the shooting-star show was expected on the East Coast in the wee hours Thursday morning. The National Weather Service forecast thickening clouds across much of the Northeast, but mostly clear skies southward.
However, astronomical calculations put the best spectacle in the Middle East and Europe.
Up to 20,000 shooting stars per hour were predicted during the meteor shower, which occurs when dust and ice shed by the comet Tempel-Tuttle streak into the Earth's atmosphere at 40 miles a second and burn up.
Since the orbiting comet dumps extra debris every 33 years when it races past the sun, the chances for a meteor storm rise very 33 years. The last great storm was 1966, with a peak of 144,000 shooting stars per hour. A typical year might yield just 20 per hour.
A NASA network of observing stations tallied the Leonid meteor count at 20 to 40 per hour early Wednesday, according to staffer Steve Roy, at the Marshall Space Flight Center in Huntsville, Ala. The number of shooting stars and fireballs was expected to swell during the night.
On Tuesday night, fireballs streaked across the sky and stirred panicky calls to police across the Midwest. Some feared plane crashes or UFOs. Blazing meteors also streaked across the sky above the Mediterranean Sea.
Roy said the reports could well have been the vanguard of the Leonid shower.
NASA is studying the composition of the Leonids with special equipment aboard two airplanes, hoping for clues to how organic chemicals were first brought to Earth.
But astronomy teacher David Howell at Deerfield Academy in Deerfield, Mass., said that even most professionals, like amateur stargazers, were mainly chasing "the thrill of it."
The shooting stars and fireballs can dart anywhere overhead, but all appear to come from the direction of the constellation Leo, which gives the shower its name. Look for it in the eastern sky near the horizon.