Dwarf Planet

space · pluto · solar system · discovery

Small but round. Dwarf planets are massive enough that their own gravity pulls them into a ball shape, just like real planets. But they're much smaller and don't have enough power to clear their neighborhoods of other space rocks.

Pluto's big change. Pluto was thought to be the ninth planet for 76 years until 2006, when scientists decided it was actually a dwarf planet instead. This decision surprised people all around the world.

Direct Sun orbiters. Dwarf planets orbit directly around the Sun, which makes them different from moons that orbit planets. They're real members of our Solar System, just in a smaller category.

Not quite planets. Some scientists think dwarf planets should count as planets, but since 2006 most astronomers say they don't meet all the requirements. A true planet needs to clear other objects out of its path around the Sun.