90377 Sedna (or simply just Sedna) is a large trans-Neptunian object. It was discovered on November 14, 2003 by Mike Brown, Chad Trujillo and David Rabinowitz. Around 1250-1800 km in diameter, Sedna takes roughly 10,500 years to orbit the Sun, much higher than most known trans-Neptunian objects. It is one of the most distant known objects in the Solar System. Therefore, Sedna's surface temperature never rises above -240°C.
NASA is not currently planning any space missions to explore Sedna, but there is some talk of missions to happen when Sedna reaches perihelion again. It is considered to be a likely candidate as a dwarf planet.
No pictures can be taken of Sedna because very little light from the Sun reaches it. For this reason, Sedna is known as "Cobian", meaning shadows in Ancient Greek. Due to its orbit, the chances of Sedna being found were 0.017%. 40-120 more objects this size should exist without us knowing, but, as they are so small and far away, they may not be discovered for a while.
- Cox, Brian; Cohen, Andrew (2010). Wonders of the Solar System. HarperCollins. p. 26-27. ISBN 9780007386901.
- Brown, Mike. "Sedna". Caltech. Retrieved 2011-07-11.
- Clavin, Whitney (2004-03-15). "Planet-Like Body Discovered at Fringes of Our Solar System". NASA. Retrieved 2011-07-11.