I was outside tonight and was looking up in the sky when a particularly bright star caught my eye. I looked at it and it seemed to get even brighter. I wondered if it was Mars because I remembered that when Mars was close, it was very bright.
While I was watching it, it began to dim. It continued to dim until it was barely visible and pretty much disappeared. This whole thing took about 10 seconds.
What could it have been?
Almost sounds like an iridium flare except that those satelites are pretty obviously moving. It certainly freaked me out when I saw one.
It did appear to move very, very slowly, but then it got so dim that I couldn’t really see it anymore.
If it was moving, and given your location and the time (within about 2 hours of sunset), I’d concur with WarmNPrickly that it was an Iridium flare.
Here’s a pretty cool site that lets you find out when satellites are visible overhead:
Then I’d bet pretty good money thats what you saw. Satelites other than iridium do that so you might have seen one of those. I don’t know for sure what I saw way back when, but a satelite was the only explanation. I didn’t read about these flares until years later. The one I saw was clipping along at a pretty good pace. It helped that I was at the base of the Grand Canyon at the time so I had no trouble seeing it even after the flare.
Cool! I think that’s what it was 
Don’t Iridiums have a fairly apparent, fairly quick speed across the sky? They’re only about 500 miles up right? Wouldn’t they have an apparent motion similar to the ISS, which is fairly fast? This seems to conflict a bit with FloatyGimpy’s description of “very very slow” motion.
Here’s a YouTube movie of an Iridium satellite flaring, for reference.
ETA: the ISS is apparently less than 1/2 the height of an Iridium, at 215 miles up. But I’d still think an Iridium would appear to be moving relatively quickly. No?
It was like this http://www.youtube.com/watch?v=iftO1k41fC4&feature=related