Sedna which is most likely a dwarf planet was discovered by Michael Brown, Chad Trujillo and also David Rabinowitz on the 14th November 2003.It is 88AU from the Sun at the present, approximately 3 times as distant as Neptune. Sedna is the furthest orbit from the Sun compared to other dwarf planet candidate. It can be detected by using advanced software together with long exposures.

Its aphelion is about 975 AU and perihelion at 76.16 AU approximately, which results in a high elliptical orbit. It was the furthest object ever observed in a solar system when it was first discovered. Eris was found at 97 AU later on. Its orbital period is not known precisely. However, it was calculated that it is in between 10.5 to 12 thousand years. Thus, in year 2114, Sedna will overtake Eris and become the farthest spheroid which orbits the Sun.

Sedna was said to have a long rotational period usually from 20 to 50 days. Hence, a search was made for a natural satellite which is most likely the cause for long rotation. However, there was none that orbits the planetoid.

Besides that, it has an absolute magnitude the value of 1.6. Estimation has been made where it has an albedo of 0.16 to 0.30 which then give it a diameter between 1200 km to 1600 km. It was considered the largest object found at the time of its discovery. Now, it is assumed to be the fifth largest trans-Neptunian object, after Eris, Pluto, Makemake and Haumea.

Observations done from Chile imply that Sedna is among the reddest object that exists in the solar system. It appears to have little methane ice on its surface, unlike Pluto and Charon. Chad Trujillo and his colleagues said that the red colour is mostly likely caused by tholin.

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