Dull steady white light, high altitude, fast moving then faded (ascended) N to S in south Cook County IL skyI was observing the sky for a few minutes and noticed several aircraft going in different directions. I spotted (and heard) a propeller driven and also several jet aircraft. As they progressed across the sky I could hear them as well. They were at varying altitudes as observed. All these aircraft had typical blinking lights as commonly seen on commercial aircraft. I spotted, then heard, a jet coming south, and it passed my location slightly to the east. I could hear its engine sound and I estimate its altitude at approximately 5000 feet. Then I spotted another light object trailing behind the jet by several seconds and going in the same general direction. It was a very steady non-blinking white light and seemed to be at a much higher altitude. It was unusual. The light was bright but not glaringly so. No sound came from this object as it passed which added to the impression it was at very high altitude. It proceeded across the sky in about the same time fram! e as the previous jet. So I estimate its speed to be much faster than the jet in order for it to cover the same distance in the sky in that short amount of time. Then it quickly faded out. The visual impression is that it just ascended out of the atmosphere.I have observed objects before in the sky that I could not identify. I reported one here several years ago, and one to MUFON. I received a follow-up inquiry. In that case, I made further observations of the area of the sky where I'd seen the later object for many days, to be fair and thorough and possibly see an explainable repeat of the sighting. After my followup observations I determined I could have seen explainable, if even unlikely, naturally occurring phenomena, and I explained that in detail in my followup answers. That is how I answered the follow-up inquiry. I keep a healthy skepticism. I do not go looking for unexplained sightings, I simply occasionally sit and relax and look at the night sky. I am always ready to accept the most likely reasonable explanation. I think that what sightings are most likely to be, they probably are, and have no illusions or belief agenda to see them to be labeled as “extraterrestrial.” I will not report a sighting unless I can't understand what it is. Only then I think it is my obligation to file a report that might be corroborated or possibly support another's sighting of the same object.