On yesterday's
Coast to Coast AM, host George Noory interviewed Seth Shostak of SETI. His findings are that the object appears to be approx. 1300 miles in altitude. It transected 35 degrees of the sky in 20 minutes, meaning it venured 5000 miles in the duration of the image capture. His best guess at this time is that it represents a fuel discharge (excess fuel dump) from a Centaur rocket that launched a DISH Network satellite into geosynchronous orbit.
However, also interviewed was planetary scientist David Grinspoon who stated it is currently a genuine mystery. He finds the satellite theory credible, but he said "it's not an open and shut case."
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There is an ongoing discussion of this phenomenon here:
http://bb.nightskylive.net/asterisk/viewtopic.php?t=291