My husband and i were driving east on I-90 from La Crosse just a couple miles from Sparta, Wis. when we saw at the exact same time what we both thought was an explosion in the sky. It was 11:39 p.m. 9/10/17 by our car clock. We both instantly said in unison "What the hell was that?". It was located high in the sky, about the height of the moon, there was no trail or tail at all, it was like a star exploded, not like any meteor that we have ever seen (and we have been sky watchers for decades). The flash was all at once, lasted just over a second, it was blue white like an electrical arch. We once had a transformer on our property hit by lightening and explode, it caused the night to look like daylight, this object did the same, and it left a lasting image in our eyes like when a camera flash goes off close to your face, It was frankly terrifying. We considered that it might have been a missle or a bomb exploding because we were in close proximity to both Fort McCoy and Camp Douglas, but it had absolutely no trail of any kind, and left no smoke or any trace that it had been there, it just flare out of nowhere, it was blinding, and then it was gone.