It appears to be a glitch in the imagery, I suppose it would have been the glare from the sun.
And by the way, Welcome to GEH!
Seems that there is some spacecraft at Pollux, but I have no idea of what it is... will anyone check this one??
No it is some type of human lunar space exploration vehicle... Though I cant find anything that would be up there -.-
"I don't expect you to understand the principle's of intelligance,
but for god sake's, the television is NOT a bathroom!"
It looks like a satellite in orbit around earth to me.
With the massive number of things we have in orbit these days, I would be very surprised if there were no other examples of this in Sky. Depending on how many photos were taken each night, and at what resolution, then there may be many, many more waiting to be found.
Great catch though, no doubt about it.