Planet Formation

An artist's rendering shows one theory of how certain large planets called gas giants might form around a young star. In this recipe, gravity causes the disk of gas and dust circling the star to collapse into several dense clouds, shown as bright clumps in this drawing. Each cloud shrinks rapidly, creating a core surrounded by gas. "It's a pretty picture," says astrophysicist Alan Boss, a primary proponent of the theory. But he admits there is much work left to do to flesh out the scenario. "It's still just a fairy tale."