Sedna

dwarf planet · distant · icy world · mysterious

Ultra-far dwarf planet. Sedna orbits the Sun far beyond Neptune, in the outermost reaches of the Solar System. It takes an incredibly long time to complete one orbit.

Frozen surface. Sedna's surface is made of solid water ice, carbon dioxide ice, and ethane ice mixed with reddish chemicals called tholins. This icy mixture is similar to other distant objects orbiting the Sun.

Roughly 1,000 km wide. Sedna is huge, about 1,000 kilometers across. It's tied with Ceres as the largest dwarf planet that we know has no moons orbiting it.

Discovered in 2003. Astronomers found Sedna in 2003 using telescopes. Its name comes from an Inuit goddess of the ocean, fitting for such a mysterious, isolated world.