The object, which lit up the sky shortly after 10 p.m. 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. Wednesday night, said William Ailor, director of the Center for Orbital and Reentry Debris Studies at the Aerospace Corporation 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.

(The University of Wisconsin-Madison’s Department of Atmospheric and Oceanic Sciences has a series of time lapse photos of the event as seen from Madison; an Iowa sheriff’s department captured video of the flash that’s been posted on YouTube.)

Christine McMorris was in her Woodstock 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 last 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.

Becky Hoffman, who lives on a farm near Dixon, said she and her husband were getting ready for bed when they looked out and saw a “big glow” in the sky. She found it strange because the air was clear of storm clouds. She said she is about an hour and a half from the Wisconsin border and noticed the light north of her home.

“We thought it might have been a transformer blowing up in the area,” she said, but she dismissed it because she did not hear any explosions.

She said it was a reddish orange glow to it and she didn’t think anything of it until she turned on the radio this morning and heard that it was a meteor.

“That’s what it was, I saw it,” said Hoffman. “I thought it was pretty exciting, I just want to know where it ended up at. Did it disintegrate into the skyline or did it actually hit ground?”

In a statement on its Web site, the National Weather Service office in the Quad Cities said: 
“Just after 10 pm CDT Wednesday evening April 14th, a fireball or very bright meteor was observed streaking across the sky. The fireball was seen over the northern sky, moving from west to east. 

“Well before it reached the horizon, it broke up into smaller pieces and was lost from sight. The fireball was seen across Northern Missouri, Illinois, Indiana, and Southern Wisconsin. Several reports of a prolonged sonic boom were received from areas north of Highway 20, along with shaking of homes, trees and various other objects including wind chimes. As of late Wednesday evening, it is unknown whether any portion of this meteorite hit the ground.”

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.

WGN Radio’s Greg Jarrett and Jim Wiser contributed to this story.

— William Mullen, Liam Ford and Carlos Sadovi

Click HERE to see a WGN-Radio video and audio report on this story.