Until a few years ago, scientists believed our Solar System contained nine planets. The discovery of a planet-like object called Eris in 2005 changed all that, leading to the creation of a new class of objects called dwarf planets. Now we have eight planets and an ever-growing family of dwarf planets. There are five official dwarf planets, and a large group of other objects that meet the criteria to be dwarf planets but have not yet been designated as such. One of these is 90377 Sedna, also known as TNO Sedna (TNO is short for Trans Neptunian Object). Learn more:
– Sedna was discovered on November 14, 2003, by a team consisting of Mike Brown from the California Institute of Technology, Chad Trujillo from the Gemini Observatory, and David Rabinowitz from Yale University.
– Sedna is located in the region of space beyond the planet Neptune, known as the scattered disc. It is currently about 86 Astronomical Units from the Sun, though its closest distance is about 76 AU, and its farthest is a whopping 960 AUs! One AU is equal to the distance between the Earth and the Sun — about 92,957,000 miles.
– It takes Sedna approximately 11,400 years to orbit the sun, giving it one of the longest orbital periods of any known object in our Solar System. Scientists believe it takes Sedna about 10 hours rotate once on its axis.
– The surface of Sedna is believed to be comprised mainly of ices — made of water, methane, and nitorgen — as well as tholins, complex organic molecules created by the effects of ultraviolet light on simpler organic molecules. Sedna’s surface color is an exceptionally bright red, which is probably caused by the tholins.
– The size of Sedna is estimated to be between 800 and 1,100 miles in diameter, making it a bit smaller than Pluto.
– Sedna, is named after the Inuit goddess of the sea, said to live at the bottom of the Arctic Ocean. The name was chosen due to the frigid region of space where it is located.
– Sedna has no known moons.
– The average temperature on Sedna is less than -400° F, making it the coldest known body in our Solar System.
– Sedna is probably too small to have an appreciable atmosphere. Ice on its surface sublimates directly into vapor and escapes into space.
– Sedna, like most Trans Neptunian Objects, can only be seen through very high-powered telescopes.