Sedna is the provisional name for the astronomical object 2003 VB16, discovered by Mike Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003, and announced on March 15, 2004.
Sedna has an estimated diameter of between 1180 and 2360 kilometres and is the largest object found in the solar system since Pluto was discovered in 1930. It is further from the sun than Pluto, and has a highly elliptical orbit, with its aphelion estimated at 850 AU and its perihelion at about 76 AU (±7 AU). Its orbit takes about 10,500 years. Too far out to be considered a Kuiper belt object, the discoverers have argued that Sedna actually belongs to the Oort cloud, although it is a great deal closer than expected for an Oort cloud object.
Because of its cold, distant nature, it is named after Sedna, the Inuit goddess of the sea, who was believed to live in the cold depths of the Arctic Ocean.
The discovery of Sedna has also re-raised the question which astronomical objects should be considered planets and which should not. Even though on March 15 2004, several news sources reported the tenth planet has been discovered, it seems unlikely that Sedna will be called a planet; however, with Sedna not being classified as a planetary body, the justification for Pluto's classification as one also becomes more questionable.