Sedna

Dwarf Planet· orbits the Sun

Sedna is a distant, very red world on one of the most extreme orbits known — swinging from about 76 AU out to roughly 937 AU and taking around 11,400 years to circle the Sun, never approaching the planets. That 'detached' orbit makes it a candidate inner-Oort-cloud object. No spacecraft has visited, and even its size, mass and rotation are only loosely known.

Open in 3D viewSee Sedna in the live, interactive 3D map

Key facts

Radius

500 km

8% of Earth's radius

Day length

10.00 hours

Year

~13,000 Earth years

Distance from Sun

541 AU

Moons

None

none known

Science

Physical

Radius: 500 km · 8% of Earth's radius

Orbital

Distance from the Sun: 82.9 AU
Semi-major axis: 541 AU
Eccentricity: 0.8593
Inclination: 15.29 °
Orbital period: 12594.16 years
Perihelion: 76.2 AU
Aphelion: 1.01e+03 AU
Mean orbital velocity: 1.28 km/s

Rotation

Rotation period: 10.00 hours

Composition

Bulk composition: One of the reddest known surfaces, consistent with tholins (sunlight-processed organics) over methane, nitrogen and water ices inferred from spectroscopy. With no detected moon its mass is unmeasured and the interior is entirely unconstrained — the data is genuinely limited.
Surface imagery: No real surface imagery exists — this object has never been visited; color is approximate, inferred from spectroscopy.

Radiation & temperature

Insolation: 0.00000341 S⊕ · 1/293,009 of the sunlight Earth receives
Geometric albedo: 0.32
Equilibrium temperature: 11 K (-262 °C)

Discovery & history

Discovered: November 14, 2003
By: Mike Brown, Chad Trujillo and David Rabinowitz
Method: Photographic plates
Name: Sedna, the Inuit goddess of the sea who lives in the cold depths of the Arctic Ocean — chosen for the most distant, coldest known body at the time.

Sedna was discovered on 14 November 2003 by Mike Brown, Chad Trujillo and David Rabinowitz (provisional designation 2003 VB12) and announced in March 2004. It moves on one of the most extreme orbits known, swinging from about 76 AU out to roughly 937 AU over some 11,400 years and never coming near the planets — a 'detached' object that may belong to the inner Oort cloud. Its deep-red surface is among the reddest in the Solar System. Brown named it for Sedna, the Inuit goddess who lives in the frigid depths of the Arctic Ocean, befitting the coldest, most remote world then known.

Images

Artist's impression of Sedna, lit by a tiny, distant Sun — not a photograph — NASA, ESA & Adolf Schaller (STScI) (public domain) · Wikimedia Commons

Images from open archives · credit shown per image