By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - A baseball-sized meteor blasted over the southeastern United States on Monday night, creating a bright streak of light, a sonic boom and a ruckus on Twitter, officials said on Tuesday.
The meteor appeared at 9:18 p.m. EDT over Alabama, traveling at about 76,000 mph. It exploded 25 miles above Woodstock, Alabama, located about 30 miles from Birmingham.
"Objects of this size hit the Earth's atmosphere on a daily basis, but this one happened near Birmingham, which is a fairly decently sized city and lot of people saw it," Bill Cooke, head of NASA's Meteoroid Environment Office at the Marshall Space Flight Center in Huntsville, Alabama, told Reuters.
Many of the more than 180 eyewitness reports came from people attending a Mumford & Sons concert in Birmingham.
"This one wasn't at 2 in the morning, so a lot of people were out and about," Cooke said.
"I saw what I first thought was a falling star and then it turned bright green," an observer from Anniston, Alabama, posted on the American Meteor Society website.
"I saw it near Dallas Highway in Marietta, (Georgia), near the National Battlefield," wrote another witness. "At first, I thought it was an errant firework, but it was bigger, neon green, came straight down and then disappeared."
Scientists calculated the meteor's orbit and determined that it came from an unknown comet. It exploded so low in Earth's atmosphere that it triggered a sonic boom.
The meteor was too bright to be picked up by NASA's All-sky Fireball Network, which tracks meteors brighter than Venus with 12 cameras in the eastern United States and New Mexico but whose parameters are set to screen out things like lightning.
The network did detect nearly two dozen other meteors on Monday night, including five that are part of the little-known annual Epsilon Perseids meteor shower, which peaks in early- to mid-September.
Sky watchers also are on the lookout for Comet ISON, which is due to pass by Mars this month and by Earth in November.
The comet, which was discovered last September by a pair of amateur astronomers in Russia, is expected to pass relatively close to the sun on November 28. As it approaches, heat from the sun vaporizes ice in the comet's body, creating a bright tail.
But so far, Comet ISON hasn't brightened as much as astronomers had predicted.
"People are no longer thinking it is going to be visible in daylight," Cooke said.
(Editing by Jane Sutton and Phil Berlowitz)