90377 Sedna (or simply just Sedna) is a 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. 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 planning any missions to explore Sedna. 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%. Hypothetically, 40-120 more objects this size should exist without our knowledge.
- Cox, Brian; Cohen, Andrew (2010). Wonders of the Solar System. HarperCollins. p. 26-27. ISBN 9780007386901.
- Brown, Mike. "Sedna". Caltech. http://www.gps.caltech.edu/~mbrown/sedna/. Retrieved 2011-07-11.
- Clavin, Whitney (2004-03-15). "Planet-Like Body Discovered at Fringes of Our Solar System". NASA. http://www.nasa.gov/vision/universe/solarsystem/planet_like_body.html. Retrieved 2011-07-11.