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. 