Sedna (dwarf planet)

90377 Sedna
Single fuzzy white dot with lots of background noise
Low-resolution image of Sedna by the Hubble Space Telescope, March 2004
Discovery[1]
Discovered byMichael Brown
Chad Trujillo
David Rabinowitz
Discovery date14 November 2003
Designations
(90377) Sedna
Pronunciation/ˈsɛdnə/
Named after
Sedna (Inuit goddess of sea and marine animals)
2003 VB12
TNO[2] · detached
sednoid[3] dwarf planet
AdjectivesSednian[4]
Symbol⯲ (mostly astrological)
Orbital characteristics[2]
Epoch 31 May 2020 (JD 2458900.5)
Uncertainty parameter 2
Observation arc30 years
Earliest precovery date25 September 1990
Aphelion937 AU (140 billion km)[5][a]
Perihelion76.19 AU (11.4 billion km)[6][5][7]
506 AU (76 billion km)[5] or 0.007 ly
Eccentricity0.8496[5]
11390 yr (barycentric)[a]
11,408 Gregorian years
1.04 km/s
358.117°
0° 0m 0.289s / day
Inclination11.9307°
144.248°
≈ 18 July 2076[6][7]
311.352°
Physical characteristics
Dimensions906+314
−258 km[8]
> 1025±135 km
(occultation chord)[9]
10.273±0.002 h
(~18 h less likely)[10]
0.410+0.393
−0.186[8]
Temperature≈ 12 K (see note)
(red) B−V=1.24; V−R=0.78[11]
20.8 (opposition)[12]
20.5 (perihelic)[13]
1.83±0.05[14]
1.3[2]

Sedna (minor-planet designation: 90377 Sedna) is a dwarf planet in the outermost reaches of the Solar System, orbiting the Sun beyond the orbit of Neptune. Discovered in 2003, the planetoid's surface is one of the reddest known among Solar System bodies. Spectroscopy has revealed Sedna's surface to be mostly a mixture of the solid ices of water, methane, and nitrogen, along with widespread deposits of reddish-colored tholins, a chemical makeup similar to those of some other trans-Neptunian objects. Within the range of uncertainties, it is tied with the dwarf planet Ceres in the asteroid belt as the largest dwarf planet not known to have a moon. Its diameter is roughly 1,000 km (most likely in between those of Ceres and Saturn's moon Tethys). Owing to its lack of known moons, the Keplerian laws of planetary motion cannot be employed for determining its mass, and the precise figure remains as yet unknown.

Sedna's orbit is one of the widest known in the Solar System. Its aphelion, the farthest point from the Sun in its elliptical orbit, is located 937 astronomical units (AU) away.[5] This is some 31 times the distance of Neptune's aphelion, and 19 times that of Pluto, spending most of its highly elongated orbit well beyond the heliopause, the boundary beyond which the influence of particles from interstellar space dominates over that of the Sun. Sedna's orbit is also one of the most narrow and elliptical discovered, with an eccentricity of 0.8496. This means that its perihelion, or point of closest approach to the Sun, at 76 AU is around 12.3 times closer than its aphelion. At perihelion, Sedna is only 55% further than Pluto's aphelion. As of January 2024, Sedna is near perihelion, 83.55 AU (12.50 billion km) from the Sun,[15] and 2.8 times farther away than Neptune. The dwarf planets Eris and Gonggong are presently farther away from the Sun than Sedna. It is suggested that an exploratory fly-by mission to Sedna near its perihelion through a Jupiter gravity assist could be completed in 24.5 years.[16]

Due to its exceptionally elongated orbit, the dwarf planet takes approximately 11,400 years, over 11 millennia, to return to the same point in its orbit around the Sun. The International Astronomical Union (IAU) initially considered Sedna to be a member of the scattered disc, a group of objects sent into high-eccentricity orbits by the gravitational influence of Neptune. However, several astronomers who worked in the associated field contested this classification as even its perihelion is far too distant for it to have been scattered by any of the currently known planets. This has led some astronomers to informally refer to it as the first known member of the inner Oort cloud. The dwarf planet is also the prototype of a new orbit class of objects named after itself, the sednoids, which include 2012 VP113 and Leleākūhonua, all celestial bodies with large perihelion distances and extremely elongated orbits.

The astronomer Michael E. Brown, co-discoverer of Sedna, believes that studying Sedna's unusual orbit could yield valuable information on the origin and early evolution of the Solar System.[17][18] It might have been perturbed into its orbit by a star within the Sun's birth cluster, or captured from a nearby wandering star, or to have been sent into its present orbit through a close gravitational encounter with the hypothetical 9th planet, sometime during the solar system's formation. The statistically unusual clustering to one side of the solar system of the aphelions of Sedna and other similar objects is speculated to be the evidence for the existence of a planet beyond the orbit of Neptune, which would by itself orbit on the opposing side of the Sun.[19][20][21]

  1. ^ Cite error: The named reference discovery was invoked but never defined (see the help page).
  2. ^ a b c Cite error: The named reference jpldata was invoked but never defined (see the help page).
  3. ^ Cite error: The named reference DES was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference sednian was invoked but never defined (see the help page).
  5. ^ a b c d e Cite error: The named reference barycenter was invoked but never defined (see the help page).
  6. ^ a b Cite error: The named reference Perihelion2076 was invoked but never defined (see the help page).
  7. ^ a b Cite error: The named reference AstDyS2076 was invoked but never defined (see the help page).
  8. ^ a b Lellouch, E.; Santos-Sanz, P.; Lacerda, P.; Mommert, M.; Duffard, R.; Ortiz, J. L.; Müller, T. G.; Fornasier, S.; Stansberry, J.; Kiss, Cs.; Vilenius, E.; Mueller, M.; Peixinho, N.; Moreno, R.; Groussin, O. (29 September 2013). ""TNOs are Cool": A survey of the trans-Neptunian region: IX. Thermal properties of Kuiper belt objects and Centaurs from combined Herschel and Spitzer observations⋆⋆⋆". Astronomy & Astrophysics. 557: A60. Bibcode:2013A&A...557A..60L. doi:10.1051/0004-6361/201322047. hdl:10316/80307. ISSN 0004-6361.
  9. ^ Cite error: The named reference Rommel2020 was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Gaudi2005 was invoked but never defined (see the help page).
  11. ^ Cite error: The named reference Tegler was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference AstDys was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference Horizons2076 was invoked but never defined (see the help page).
  14. ^ Cite error: The named reference herschel was invoked but never defined (see the help page).
  15. ^ "Star Maps of Asteroid 90377 Sedna (2003 VB12) | TheSkyLive". 10 January 2024. Archived from the original on 10 January 2024. Retrieved 10 January 2024.
  16. ^ Cite error: The named reference McGranaghan was invoked but never defined (see the help page).
  17. ^ Cite error: The named reference fussman was invoked but never defined (see the help page).
  18. ^ Cite error: The named reference Chang_2016 was invoked but never defined (see the help page).
  19. ^ Cite error: The named reference Mike was invoked but never defined (see the help page).
  20. ^ Cite error: The named reference Lakdawalla_2014 was invoked but never defined (see the help page).
  21. ^ Cite error: The named reference Evidence for a Distant Giant Planet was invoked but never defined (see the help page).


Cite error: There are <ref group=lower-alpha> tags or {{efn}} templates on this page, but the references will not show without a {{reflist|group=lower-alpha}} template or {{notelist}} template (see the help page).