Aurora Borealis

According to Triton College astronomer Dan Joyce, this was the Chicago area's first significant northern lights event in nearly seven years.  By most accounts, the display peaked between 8:30 and 9:15 p.m.

http://www.chicagotribune.com/news/local/breaking/chi-aurora-borealis-makes-a-rare-area-appearance-20111025,0,6390834.story

One photographer west of Madison, Wis., claims the display was so bright "it lit up the ground."

http://dakotalapse.com/?p=581