April 16, 2010 in Nation/World

Fireball lights up Midwest sky

Scientists say object most likely large meteor
William Mullen, Liam Ford And Carlos Sadovi Chicago Tribune
 
University of Wisconsin-Madison Department of Atmospheric and Oceanic Sciences photo

This photo from a rooftop webcam released Thursday by the University of Wisconsin-Madison shows a fireball as it passed over Madison, Wis., on Wednesday night. University of Wisconsin-Madison Department of Atmospheric and Oceanic Sciences
(Full-size photo)

CHICAGO – A fiery ball of light witnessed by thousands as it swept over the upper Midwest on Wednesday night was almost certainly a large meteor that probably left a trail of debris across southern Wisconsin, asteroid experts say.

The path of the meteor was tracked by Doppler radar at two National Weather Service stations.

“It has the appearance that is completely consistent with being a bright meteor,” said Mark Hammergren, an Adler Planetarium astronomer who specializes in asteroids, after viewing the Doppler images.

The object, which lit up the sky shortly after 10 p.m. CDT Wednesday across parts of Missouri, Iowa, Minnesota, Illinois and Wisconsin, was very likely a piece of an asteroid, a rocky planetoid formation that orbits the sun, he said. Almost all meteors come from asteroids.

It almost certainly was not from debris trailing a comet or part of a meteor shower associated with a comet, as earlier reports have speculated, Hammergren said.

“We won’t know for sure until we get specimens” of whatever the object was, if pieces of it survived the fiery plunge through the Earth’s atmosphere, he said. But it was so large, he said he was fairly certain some may be found. Technically, if pieces of a meteor survive the impact, they are known as “meteorites.”

There was no “space junk” satellite debris that would have de-orbited into the atmosphere over that part of the U.S. on Wednesday night, said William Ailor, director of the Center for Orbital and Reentry Debris Studies at the Aerospace Corp. in California, ruling out that it could have been a piece of an old satellite.

According to the weather service’s Milwaukee office, officials there, in LaCrosse, Wis., Davenport and Des Moines, Iowa, and in St. Louis and Kansas City, Mo. received “numerous reports of a fireball” about the same time people began contacting Milwaukee-area officials about the flare.

National Weather Service radar in LaCrosse, Wis., showed the object at between 6,000 and 12,000 feet, heading from northwest to southeast over Grant and Iowa counties.

Christine McMorris was in her Woodstock, Ill., home Wednesday evening looking out of her kitchen window as she washed dishes and talked with a friend when she noticed a bright light coming from the sky.

“All of a sudden out of the corner of my eye, I saw this huge ball of fire and a huge light,” said McMorris. “I was like, what the hell was that?”

She had seen many shooting stars during her travels to the Western United States. But Wednesday night put those to shame, she said.

“They are minuscule compared to this, it was enormous,” she said.

She said as the meteor traveled closer to the surface, its intensity diminished until she lost sight of it during the approximately five to 10 seconds it took to drop. She said it didn’t have a tail.

“It was truly spectacular,” she said.

Hammergren said the apparently large size of the meteor indicates pieces may well have survived and hit the ground.

“The strength of this was comparable to others where multiple fragments have been recovered, he said, guessing that as a meteor prior to hitting and exploding in the atmosphere may have weighed “hundreds of pounds.”

Similarly sized meteors have produced meteorite fragments from the size of grains of sand to fist size and football-sized chunks.

Meteorites are so highly prized by scientists, collectors and dealers, that teams of searchers already are preparing to go to an area in southwest Wisconsin where fragments most likely would have crashed into the ground, he said.


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