Planet
Sedna
Trans-Neptunian object
Distant body in the outer Solar System
Photo: NASA · Public domain · Wikimedia Commons
Sedna is a dwarf planet in the outermost reaches of the Solar System, orbiting the Sun far beyond the orbit of Neptune. It was discovered in 2003, and is roughly 1,000 km in diameter. Spectroscopic analysis has revealed its surface to be a mixture of the solid ices of water, carbon dioxide, and ethane, along with sedimentary deposits of methane-derived, reddish-colored tholins, a chemical makeup similar to the surfaces of other trans-Neptunian objects. Sedna is not expected to have a substantial atmosphere. Within the range of uncertainty, it is tied with Ceres in the asteroid belt as the largest dwarf planet not known to have a moon. Owing to its lack of known moons, Sedna's mass and density remain unknown.
Description from Wikipedia (CC BY-SA 4.0).
Key facts
Distance
Outer solar system
Orbital period
12,883 years
Discovered
2003 · Michael E. Brown
