Hulk was betrayed by the Reed Richards, Tony Stark, Dr. Strange, and Black Bolt (the Illuminati). He was sent into space to stop a global threat. Hulk saves the world and when they sent him his ride home (a space ship) it started going in the wrong direction. Richards gave him some speech about how they did it for his better interest. They wanted to let him live on another planet with no intelligent life where he can finally be left alone.
Well, things went wrong and he got sucked into a wormhole and was spat out onto some other planet. The wormhole drained his power (which is slowly returning) and now he's on this planet where people have technology that can actually harm him! So Hulk is being paired up with a motley crew of aliens from different reaches of space.
Greg Pak's writing is perfect for the Hulk. This is an event that will last until feb. 2007 (If I remember correctly)
The first four-issue arc has already come out, and the first issue of the second arc has already come out. It is really good. It shouldn't be too hard to track down the last four issues, so I recommend you try to catch up because this really is the best Hulk story in years.
For more info on how Hulk got sent to space check out the New Avengers: Illuminati one shot. It's really well written.
Anyway, because Hulk will be in space this whole time he will not be a part of Civil War. It kinda sucks but don't worry, he'll have plenty of fun wreaking havoc when he returns.
Hope this helped!
OVER A YEAR OF PLANET HULK!!! Hope this helps! 
