Our perception of the outer edge of our solar system has changed dramatically in the last few years. Since 2002, we have found several objects in our solar system half Pluto's size or larger. These "planetoids" are too small to be considered planets, but large enough that they retain some of the properties commonly associated with planets. The most extreme of these, Sedna, is significantly farther from the Sun than anything else known in our solar system, and its orbit gives us clues to how the solar system formed 4.5 billion years ago. It is very likely that several more such planetoids will be discovered in the next few years, possibly including something larger than the planet Pluto.

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