Can anyone identify this? A few minutes ago, at 2145 Pacific Daylight
Time, I happened to look up and saw a very bright, fast moving object
going through Ursa Major. I first saw it underneath the bend in the
handle and watched it move north until it faded out near the star at
the bottom of the dipper. It was 0 or -1 magnitude, maybe brighter,
and went to invisible over the 10 seconds or so I saw it.

The only things I've ever seen this bright were Mir or the ISS, and
the latter isn't above us right now. Could it have been a booster from
today's shuttle launch?