Sedna never comes closer to the Sun than 76 AU and takes more than 11,000 years to go round
Sedna is about 1,000 km across, one of the reddest objects known. Mike Brown, Chad Trujillo and David Rabinowitz found it in November 2003 and named it for the Inuit goddess of the sea. Its orbit is so stretched that it never comes closer than 76 AU, far beyond Neptune's reach, and it travels out to about 1,000 AU. Something must have pulled it into that orbit: a passing star when the Sun was young, or an undiscovered planet far out. It reaches its closest point to the Sun around 2076, the best chance for a spacecraft flyby for thousands of years.
Sedna is now about 83 AU from the Sun and closing in.
What is known about the surface of Sedna
Atmosphere
none
Reflectivity
reflects about 32% of sunlight
Day
10.27 hours
Sedna compared with Pluto
Pluto is the yardstick for the outer solar system: 2,376 km across, 39.5 AU from the Sun on average, on a 248-year orbit.
Sedna is beyond the reach of backyard telescopes
At about magnitude 20.7, Sedna is far too faint for amateur telescopes and is followed with some of the largest telescopes on Earth.
Sedna among the dwarf planets and distant worlds
Dwarf planets and candidates beyond Neptune, by distance27
| Name | Region | Average distance (AU) | Diameter (km) |
|---|---|---|---|
| Pluto | Kuiper Belt | 39.24 | 2,376 |
| Orcus | Kuiper Belt | 39.34 | 910 |
| Ixion | Kuiper Belt | 39.35 | 697 |
| Achlys | Kuiper Belt | 39.63 | 772 |
| Ritona | Kuiper Belt | 41.55 | 679 |
| Máni | Kuiper Belt | 41.59 | 796 |
| Goibniu | Kuiper Belt | 41.81 | 680 |
| Salacia | Kuiper Belt | 42.12 | 866 |
| Uni | Kuiper Belt | 43 | 610 |
| Haumea | Kuiper Belt | 43.01 | 1,595 |
| Quaoar | Kuiper Belt | 43.15 | 1,110 |
| Varuna | Kuiper Belt | 43.18 | 668 |
| Makemake | Kuiper Belt | 45.51 | 1,430 |
| Varda | Kuiper Belt | 45.54 | 740 |
| Chaos | Kuiper Belt | 46.11 | 600 |
| Aya | Kuiper Belt | 47.3 | 768 |
| 2013 FZ27 | Kuiper Belt | 48.14 | 570 |
| Chiminigagua | Scattered disc | 58.79 | 742 |
| Gonggong | Scattered disc | 66.89 | 1,230 |
| Eris | Scattered disc | 68 | 2,326 |
| Gǃkúnǁʼhòmdímà | Scattered disc | 74.59 | 614 |
| 2015 RR245 | Scattered disc | 81.3 | 670 |
| 2014 UZ224 | Scattered disc | 109.9 | 635 |
| 2012 VP113 | Detached / inner Oort cloud | 262.3 | 450 |
| 2015 BP519 | Scattered disc | 449 | 584 |
| Sedna | Detached / inner Oort cloud | 549.5 | 995 |
| Leleākūhonua | Detached / inner Oort cloud | 1,190 | 220 |
Sedna physical and orbital data
Every value in the planets dataset for Sedna
| Classification | dwarf planet candidate |
| Designation | (90377) Sedna (2003 VB12) |
| Discovered | 2003 |
| Discoverer | Michael Brown, Chad Trujillo, David Rabinowitz |
| Named for | Sedna, Inuit goddess of the sea |
| Average distance from the Sun | 549.541 AU |
| Closest to the Sun (perihelion) | 76.223 AU |
| Farthest from the Sun (aphelion) | 1022.858 AU |
| Orbital eccentricity | 0.861 |
| Orbital inclination | 11.93° |
| Orbital period | 12882 years |
| Average orbital speed | 1.27 km/s |
| Diameter | 995 km |
| Rotation period | 10.27 hours |
| Albedo | 0.32 |
| Brightest magnitude | 20.7 |
| Atmosphere | none |
| Moons | 0 |
| Rings | No |
From the site's planets dataset (planets_q426). Each row in the dataset lists its sources.