At http://phys.org/print308400922.html … a cosmic body orbiting a star about 440 light years away is causing astrophysicists a bit of a knotty problem. What is the difference between a failed star (a Brown Dwarf) and a planet. They have been observing and keeping track of the object over the last seven years but can't yet determine which of either it is. The paper, in Astrophysical Journal Letters (published this week) can also be viewed at http://arxiv.org/abs/1310.4825. It is nine times the size of Jupiter but it is 30 times further away from its host star than Jupiter is from the Sun. Is an object so massive and yet so far away from its host star a planet – or a Brown Dwarf?
The consensus view is that gas giants such as Jupiter and Saturn form by core accretion whereby other planets form from a solid core that then accretes a massive gaseous envelope – and not only that, core accretion operates most effectively closer to the parent star due to the length of time required to first form a core.