90377 Sedna
90377 Sedna (or simply Sedna; symbol ) is a trans-Neptunian object which is the farthest dwarf planet from the Sun. It was discovered on November 14, 2003 by Mike Brown, Chad Trujillo and David Rabinowitz. Around 1250-1800 km in diameter, Sedna takes roughly 11,400 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.