Editor's Note: This slideshow is a supplement to the Feature "The Chaotic Genesis of Planets" from the May 2008 issue of Scientific American.

Barely a decade ago scientists who study how planets form had to base their theory on a single example—our solar system. Now they have dozens of mature systems and dozens more in birth throes. No two are alike.

The basic idea behind the leading theory of planetary formation—tiny grains stick together and swoop up gas—conceals many levels of intricacy. A chaotic interplay among competing mechanisms leads to a huge diversity of outcomes.

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