The Adler Planetarium offers free admission to Illinois Residents on various days throughout the year. Passes must be purchased at the planetarium on the free day, with no advance purchase. Free dates are: January 3, 4, 7-12, 15-19, February 2, 5-9, 14, 19-22, June 21, August 27-31, September 9-16, October 8, 21, 24, 25, November 11, 12, 14, 15, December 1, 3-7, 10.