Sedna was discovered on November 14, 2003 by a CalTech team, using the 48-inch Samuel Oschin Telescope at Palomar Observatory. The object lies more than 8 billion miles from the Earth, making it the most distant object ever observed in the solar system. Its official IAU provisional designation was minor planet 2003 VB12, but as of September 28, 2004 it officially became known as Sedna after the Inuit goddess of arctic sea life.

The Growing Solar System Family

The orbit of 2003 UB 313 (shown in red) relative to the other planets in the solar system and Sedna (large white oval). 

The "original" nine planets are indicated as well as 2003 UB313 (in red) and part of Sedna's orbit. 2003 UB313 appears to cross inside of Pluto's orbit but this is due to the fact that 2003 UB313 is tilted by about 45º relative to the rest of the solar system.

SOURCE: Gemini Observatory

Recent spectroscopic studies of infrared light reflected from the surface of Sedna reveal that it is probably unlike Pluto and Charon since Sedna's surface does not display evidence for a large amount of either water or methane ice. Due to Sedna’s extreme distance from the Sun, the frigid surface has probably been untouched for millions of years by anything except cosmic rays and solar ultraviolet radiation.

Gemini Observatory astronomer Chad Trujillo led an effort by the same California Institute of Technology research team responsible for Sedna's original discovery to obtain spectra of this distant planetoid using the Near Infrared Imager (NIRI) on Gemini North. Their aim was to better understand the surface of this distant world and how it has evolved since its formation. “It is likely that Sedna has experienced an extremely isolated life in the outskirts of our solar system,” said Trujillo. “Out there beyond what we used to think was the edge of the solar system, interactions or collisions between bodies are probably very rare. Our observations confirm what you would expect from a surface that has been so far out in our solar system for such a long time and exposed to space weathering.”

SOURCE: Gemini Observatory

Image Credit: NASA, ESA, A. Feild (STScI)

• Sedna:  The coldest most distant place known in the solar system

• Astronomer David C. Hewitt - on Edgeworth-Kuiper objects at his Kuiper Belt Page.
• Sedna 90377 - Wikipedia
• NASA/JPL Small-Body Database Browser - Sedna

1. "Discovery Circumstances: Numbered Minor Planets (90001)-(95000)". IAU: Minor Planet Center.
2. Buie, Marc W. (2007-08-13). "Orbit Fit and Astrometric record for 90377". Deep Ecliptic Survey. 
3. Brown, Michael E.. "The largest Kuiper belt objects" (PDF)
4. Stansberry, John; Will Grundy, Mike Brown, Dale Cruikshank, John Spencer, David Trilling, Jean-Luc Margot (2007). "Physical Properties of Kuiper Belt and Centaur Objects: Constraints from Spitzer Space Telescope". University of Arizona, Lowell Observatory, California Institute of Technology, NASA Ames Research Center, Southwest Research Institute, Cornell University
5. Radius of 590 km and density of 0.97 = 8.3 × 10²⁰ kg mass. Radius of 900 km and density of 2.3 = 7.0 × 10²¹ kg mass
6. Tegler, Stephen C. (2006-01-26). "Kuiper Belt Object Magnitudes and Surface Colors"
7. "AstDys (90377) Sedna Ephemerides". Department of Mathematics, University of Pisa, Italy
8. "Horizons Output for Sedna 2076/2114" Horizons
9. "JPL Small-Body Database Browser: 90377 Sedna (2003 VB12)". 2007-11-08 last obs
10. At present, though, Eris (dwarf planet) is farther from the Sun than Sedna.
11. Lowell DES Perihelion Epoch = 2000.0 + (2479283.2278 − 2451545.0)/365.25 = 2075.9431 = (2076-1-1 - 20.7768 days) = 2075-12-11 (Julian Date Converter)
12. Morbidelli, Alessandro; Harold F. Levison (2004). "Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12 (Sedna)". The Astronomical Journal '128': 2564–2576. doi:10.1086/424617. (Original Preprint)
13. "The Challenge of Sedna". Harvard-Smithsonian Center for Astrophysics
14. Gomes, Rodney S.; John J. Matese, and Jack J. Lissauer (2006). "A distant planetary-mass solar companion may have produced distant detached objects". Icarus 184: 589–601. doi:10.1016/j.icarus.2006.05.026. http://adsabs.harvard.edu/abs/2006Icar..184..589G
15. Gaudi, B. Scott; Krzysztof Z. Stanek, Joel D. Hartman, Matthew J. Holman, Brian A. McLeod (CfA) (2005). "On the Rotation Period of (90377) Sedna". Astrophys.J. 629: L49–L52. doi:10.1086/444355. http://arxiv.org/abs/astro-ph/0503673
16. D. L. Rabinowitz; K. M. Barkume, M. E. Brown, H. G. Roe, M. Schwartz, S. W. Tourtellotte, C. A. Trujillo (2006). "Photometric Observations Constraining the Size, Shape, and Albedo of 2003 EL₆₁, a Rapidly Rotating, Pluto-Sized Object in the Kuiper Belt" (preprint on arXiv). The Astrophysical Journal 639 (2): 1238–1251. doi:10.1086/499575
17. M. Grundy, K. S. Noll, D. C. Stephens. "Diverse Albedos of Small Trans-Neptunian Objects". Lowell Observatory, Space Telescope Science Institute.
18. McKee, Maggie (2005). "Distant planetoid Sedna gives up more secrets". NewScientist.com news service
19. Alexander, Amir (18 April 2005). "Sedna: Mysterious Planetoid Slowly Yielding Up Its Secrets". The Planetary Society
20. Barucci, M. A.; D. P. Cruikshank, E. Dotto, F. Merlin, F. Poulet, C. Dalle Ore, S. Fornasier and C. de Bergh (2005). "Is Sedna another Triton?". Astronomy & Astrophysics 439: L1–L4. doi:10.1051/0004-6361:200500144
21. Jewitt, David, Morbidelli, Alessandro, & Rauer, Heike. (2007). Trans-Neptunian Objects and Comets: Saas-Fee Advanced Course 35. Swiss Society for Astrophysics and Astronomy. Berlin: Springer. ISBN 3540719571
22. Lykawka, Patryk Sofia & Mukai, Tadashi. (2007). Dynamical classification of trans-neptunian objects: Probing their origin, evolution, and interrelation. Icarus Volume 189, Issue 1, July , Pages 213-232. doi:10.1016/j.icarus.2007.01.001
23. Kenyon, Scott J.; Benjamin C. Bromley (2 December 2004). "Stellar encounters as the origin of distant Solar System objects in highly eccentric orbits". Nature 432: 598–602. doi:10.1038/nature03136
24. Evidence for an Extended Scattered Disk?
25. Jewitt, D., A. Delsanti, The Solar System Beyond The Planets in Solar System Update : Topical and Timely Reviews in Solar System Sciences , Springer-Praxis Ed., ISBN 3-540-26056-0 (2006) Preprint of the article (pdf)
26. Elliot, J. L., S. D. Kern, K. B. Clancy, A. A. S. Gulbis, R. L. Millis, M. W. Buie, L. H. Wasserman, E. I. Chiang, A. B. Jordan, D. E. Trilling, and K. J. Meech The Deep Ecliptic Survey: A Search for Kuiper Belt Objects and Centaurs. II. Dynamical Classification, the Kuiper Belt Plane, and the Core Population. The Astronomical Journal, 129 (2006), pp. preprint
27. Brown, Michael E.. "The Dwarf Planets". California Institute of Technology, Department of Geological Sciences
28. Stern–Levison parameter (using unlikely highest estimated mass) = ((7 × 10²¹) / (5.9736 × 10²⁴))^2 / 12,059 yr = 1.14 × 10⁻¹⁰ (Sedna 1.14 × 10⁻¹⁰) / (Pluto 1.95 × 10⁻⁸) = 5.8 × 10⁻³

• Discovery of a candidate inner Oort cloud planetoid (Brown et al., submitted to ApJ Letters, March 16, 2004)
• Hurt, Robert. Artist's Concept of Sedna. California, USA: Infrared Processing and Analysis Center. March 15, 2004.
• Hurt, Robert. Sedna's Orbit Comparisons. California, USA: Infrared Processing and Analysis Center. March 15, 2004.
• JPL. Most Distant Object in Solar System Discovered. Press release: Jet Propulsion Laboratory. March 15, 2004.
• Whitehourse, David. Sedna has no moon, say astronomers. BBC News, April 14, 2004.

• NASA's Sedna page (Discovery Photos)
• Mike Brown's Sedna page
• Official press release by NASA JPL/SCC
• Astronomy Picture of the Day 04 July 2004 – Artist's rendering of view from Sedna
• Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR₁₀₅ and 2003 VB₁₂ (Sedna) by Alessandro Morbidelli and Harold F. Levison
• MPEC 2004-S73: Comment on the naming of Sedna
• Distant Object Could Hold Secrets to Earth's Past
• Sedna on The Nine Planets Solar System Tour
• Hubblesite image April 14, 2004
• Orbital simulation from JPL (Java) / Ephemeris