At 3:12, I stepped out for a cigarette. It's hazy tonight along the horizon here. Almost straight up in the atmosphere, I saw a yellowish star-like object ascending at a rapid speed. I thought it might be a plane at first, but there was no sound. And it did not strobe.I live between Midway and O'Hare, and I'm familiar with the way commercial aircraft look and sound at varying altitudes. This object had no strobes, and made no sound. It was not a case of take-off lights dimming to strobes. This object was going straight up and moving away from my line of vision. When I first saw it, it looked like a very bright star and became a very small, unwavering speck in six seconds or less. I caught it out of the corner of my eye, from the south, goinging slightly north. It was well above the haze on the horizon. I was looking straight up from my balcony when I saw it. Absolutely no sound, and I have never seen nothing move out of sight that quickly, so clearly.