I don't know how much you know about Marvel Civil War (or if any of my strange posts about it made sense), but slightly before it happened, Hulk rampaged in Nevada, which caused a few innocent deaths (which he never did before, lots of injuries, yes, but no deaths).

So this secret inner circle group of heroes called the Illuminati (Iron Man, Mr. Fantastic, Dr. Strange, and Black Bolt) launched Hulk into space. They aimed for a peaceful uninhabited planet, but instead, Hulk landed on another planet full of strange and diverse aliens. The Hulk is currently involved in a year-long story (I think it's on month 5, actually) called Planet Hulk, which has been REALLY good so far. The planet has put limits on Hulk's strength, and he has some smarts (he likes to smash, but he talks somewhat intelligently).