| MadSci Network: Astronomy |
You almost certainly saw a bright meteor, also called a fireball. It was seen by other people as well, from your location in Minnesota to as far east as Pennsylvania. All meteors, from the tiniest shooting stars to the biggest fireballs, are caused by the same thing: the incandescence of a particle of space debris encountering the Earth's atmosphere at a very high speed. While ordinary shooting stars are caused by debris that is sand sized, fireballs result from larger objects: pea sized up to automobile sized. Once objects become larger than that, they have enough mass to reach the ground without being significantly slowed down, and they produce craters. Fortunately, such impacts are very rare!
A small percentage of fireballs are caused by re-entering space junk, such as expended rocket bodies. Such objects are tracked, however, and there is no indication that the event you saw was this type of fireball.
About fireballs: www.cloudbait.com/science/fireballs.html
Try the links in the MadSci Library for more information on Astronomy.