Expert and amateur astronomers question if a bright light reportedly seen by people across six Midwestern states on Thursday night was a chunk of rock or ice, or perhaps burning space junk.

Social media and online reports detail a bright green, yellow and red "fireball" that burned for seconds over central Iowa skies about 5:40 p.m. Thursday. The sighting was detailed in more than 600 online reports from witnesses in Iowa, Illinois, Kansas, Minnesota, Missouri and Nebraska received by the American Meteor Society, a nonprofit organization that promotes meteoric research.

Video from an Iowa camera provided to Minneapolis TV station KARE 11 shows the glowing object moving from south to north about 5:41 p.m. The video's authenticity has yet to be confirmed. One person in West Virginia and three people in Michigan also reported seeing the streak of light, according to the AMS.

A south-to-north flight path would be consistent with a piece of space junk - scraps from a satellite or a rocket's booster engine - re-entering the earth's atmosphere, said Steven Spangler, a professor of physics and astronomy at the University of Iowa.

Surveillance satellites commonly orbit the earth from north to south, rather than around the equator, because the path provides better coverage of the earth's surface, Spangler said. Spangler told The Des Moines Register on Friday that he was looking into videos and reports of the object to determine what it might have been.

"When you see something, these flashing lights in the sky, we call these meteors," he said. "I think most of those are actual natural objects, ... but we've been launching stuff up into space for 56 years now and some of that comes down in the form of space junk."

Pieces of so-called "space junk" are regularly tracked by the U.S. Strategic Command, which is tasked with overseeing the nation's space operations, including military satellites, Spangler said.

"Even space junk could make some sort of visible effect," said Greg Woolever, observatory director for the Des Moines Astronomical Society. "It could be pretty spectacular."

Woolever, an amateur astronomer, did not know if the object was space junk or a meteor. Although meteors are not uncommon, what would make Thursday's different was its brightness, Woolever said.

"It's uncommon for it to be making such a bright flare and being seen by so many people," Woolever said. "Since it was brighter, one wants to assume it is therefore larger, but even that comes under scientific question."

By examining the object's flight path in videos and from eyewitness reports, it's possible to track an object's path before entering the earth's atmosphere, Spangler said. Often, pieces of meteorites and ice can be tracked back to the asteroid belt, a region of space between the planets Jupiter and Mars, he said.

There were no meteor showers expected Thursday, but "sporadic meteors" often come into the earth's atmosphere, Spangler said.