B737-700
Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 423; Flight Crew Type 423
Situational Awareness
Conflict NMAC
Flight Crew Took Evasive Action
Human Factors
We were level at 5000 ft on the ENDEE 4 Arrival into MDW just before KEMPZ when ATC gave us a traffic call with 'type and altitude unknown.' About a minute later with still no TCAS alert or symbol; we visually acquired a low wing general aviation aircraft heading southeast left to right approximately 100 ft low; less than a mile in front of us. We disengaged the autopilot and executed a turn to the left to avoid. We estimate we cleared him by 100 ft vertically and 500 ft feet laterally. We contacted ATC and continued uneventfully. After the flight we did not get any questions from the passengers or Flight Attendants. I don't think they even noticed. I called Dispatch to report the event. We feel we did everything correctly and just wished all GA aircraft were more aware of jet traffic flight paths and got flight following everywhere they went.
B737-700 Captain reported an NMAC with a light aircraft in the vicinity of MDW.