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Sedna

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TRANS-NEPTUNIAN OBJECT

Sedna

An extreme trans-Neptunian object with a 10,000-year orbit — possibly a first member of the inner Oort Cloud.

Orbits Sun

Physical Properties

498 km
0.32

Orbit

Sun
506 AU
0.8549
11.93°
76.26 AU
937 AU
11400 yr

Sources & Further Reading

Numerical values (radius, mass, orbital elements, temperatures) are drawn from NASA NSSDC Planetary Fact Sheets, JPL Horizons, and the JPL Small-Body Database. Last refreshed: 2026-04-18 18:19:28.

90377 Sedna is a distant trans-Neptunian object on one of the most extreme orbits known. Its aphelion is ~937 AU and its orbital period about 11,400 years. Its highly eccentric, distantly-bound orbit — never coming closer than 76 AU from the Sun — makes it a candidate first member of the hypothetical inner Oort Cloud. Its orbit is part of the observational evidence supporting the hypothesized “Planet Nine.”