90377 Sedna

Sedna PRC2004-14d.jpg
Sedna as imaged by the Hubble Space Telescope
Discovery [1]
Discovered byMichael Brown
Chad Trujillo
David Rabinowitz
Discovery date14 November 2003
MPC designation(90377) Sedna
Named after
Sedna (Inuit goddess of sea and marine animals)
2003 VB12
TNO[2] · detached
Orbital characteristics[2]
Epoch 13 January 2016 (JD 2457400.5)
Uncertainty parameter 2
Observation arc9240 days (25.30 yr)
Earliest precovery dateSeptember 25, 1990
Aphelion≈ 936 AU (Q)[4]
1.4×1011 km
0.015 ly
Perihelion76.0917±0.0087 AU (q)
1.1423×1010 km
506.8 AU[5][4]
7.573×1010 km
≈ 11400 yr[4][a]
1.04 km/s
0° 0m 0.31s / day (n)
Inclination11.92872° (i)
144.546° (Ω)
311.29°±0.014° (ω)
Physical characteristics
Dimensions995±80 km
(thermophysical model)
1060±100 km
(std. thermal model)[7]
10.273 h (0.4280 d)
10.3 h ± 30%[2][8]
Temperature≈ 12 K (see note)
(red) B−V=1.24; V−R=0.78[9]
20.5 (perihelic)[11]

90377 Sedna is a large minor planet in the outer reaches of the Solar System that was, as of 2015, at a distance of about 86 astronomical units (1.29×1010 km; 8.0×109 mi) from the Sun, about three times as far as Neptune. Spectroscopy has revealed that Sedna's surface composition is similar to that of some other trans-Neptunian objects, being largely a mixture of water, methane, and nitrogen ices with tholins. Its surface is one of the reddest among Solar System objects. It is most likely a dwarf planet. Among the eight largest trans-Neptunian objects, Sedna is the only one not known to have a moon.[12][13]

For most of its orbit, it is even farther from the Sun than at present, with its aphelion estimated at 937 AU[4] (31 times Neptune's distance), making it one of the most distant-known objects in the Solar System other than long-period comets.[b][c]

Sedna has an exceptionally long and elongated orbit, taking approximately 11,400 years to complete and a distant point of closest approach to the Sun at 76 AU. These facts have led to much speculation about its origin. The Minor Planet Center currently places Sedna in the scattered disc, a group of objects sent into highly elongated orbits by the gravitational influence of Neptune. This classification has been contested because Sedna never comes close enough to Neptune to have been scattered by it, leading some astronomers to informally refer to it as the first known member of the inner Oort cloud. Others speculate that it might have been tugged into its current orbit by a passing star, perhaps one within the Sun's birth cluster (an open cluster), or even that it was captured from another star system. Another hypothesis suggests that its orbit may be evidence for a large planet beyond the orbit of Neptune.[15]

Astronomer Michael E. Brown, co-discoverer of Sedna and the dwarf planets Eris, Haumea, and Makemake, thinks that it is the most scientifically important trans-Neptunian object found to date, because understanding its unusual orbit is likely to yield valuable information about the origin and early evolution of the Solar System.[16][17]



Sedna (provisionally designated 2003 VB12) was discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory), and David Rabinowitz (Yale University) on 14 November 2003. The discovery formed part of a survey begun in 2001 with the Samuel Oschin telescope at Palomar Observatory near San Diego, California using Yale's 160-megapixel Palomar Quest camera. On that day, an object was observed to move by 4.6 arcseconds over 3.1 hours relative to stars, which indicated that its distance was about 100 AU. Follow-up observations were made in November–December 2003 with the SMARTS telescope at Cerro Tololo Inter-American Observatory in Chile, the Tenagra IV telescope in Nogales, Arizona, and the Keck Observatory on Mauna Kea in Hawaii. Combining those with precovery observations taken at the Samuel Oschin telescope in August 2003, and from the Near-Earth Asteroid Tracking consortium in 2001–2002, allowed to accurately determine its orbit. The calculations showed that the object was moving along a distant highly eccentric orbit, at a distance of 90.3 AU from the Sun.[18][15] Precovery images have later been found in images of the Palomar Digitized Sky Survey dating back to September 25, 1990.[2]


Brown initially nicknamed Sedna "The Flying Dutchman", or "Dutch", after a legendary ghost ship, because its slow movement had initially masked its presence from his team.[19] For an official name for the object, Brown settled on "Sedna", a name from Inuit mythology, which Brown chose partly because the Inuit were the closest polar culture to his home in Pasadena, and partly because the name, unlike Quaoar, would be easily pronounceable.[20] On his website, he wrote:

Brown also suggested to the International Astronomical Union's (IAU) Minor Planet Center that any future objects discovered in Sedna's orbital region should also be named after entities in arctic mythologies.[21] The team made the name "Sedna" public before the object had been officially numbered.[22] Brian Marsden, the head of the Minor Planet Center, said that such an action was a violation of protocol, and that some members of the IAU might vote against it.[23] No objection was raised to the name, and no competing names were suggested. The IAU's Committee on Small Body Nomenclature accepted the name in September 2004,[24] and also considered that, in similar cases of extraordinary interest, it might in the future allow names to be announced before they were officially numbered.[22]

Other Languages
Afrikaans: 90377 Sedna
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