Sedna

Overview: Sedna is one of the most distant known objects in the solar system, residing in a region sometimes called the “inner Oort Cloud.” Its extreme orbit and size make it a fascinating dwarf planet candidate.

Discovery: Sedna was discovered on November 14, 2003, by Mike Brown, Chad Trujillo, and David Rabinowitz using the Palomar Observatory. Its discovery sparked significant interest due to its extremely distant and elongated orbit.

Orbit: Sedna has a highly eccentric orbit, ranging from about 76 AU at perihelion to over 937 AU at aphelion. Its orbital period is approximately 11,400 Earth years, making it one of the longest-known orbits in the solar system. Its inclination is ~11.9°.

Size and Composition: Sedna’s diameter is estimated at 995–1,000 km. Spectroscopic observations show the presence of methane and water ice on its surface, with a reddish tint attributed to tholins. Its extreme distance results in an incredibly cold surface, likely below 30 K.

Interesting Notes: Sedna’s distant orbit may be influenced by a past stellar encounter, unseen massive objects in the outer solar system, or even a hypothetical Planet Nine. Its unique location and orbit make it a subject of ongoing dynamical studies.