How to Make a Gas Giant?

We have to watch these things cross their sun. And so basically it's best if you can see them pass a few times, so the equivalent of several of their years. So that's a long way of saying we don't have an unbiassed picture of what's going on in these other solar systems. But those other solar systems do give us a lot of clues back to jupiter. We that it must have had to form in the outer solar system, because that's basically the only place to make these big gas giants.