90377 Sedna: Wikis


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90377 Sedna
Sedna, highlighted by the green circle
Discovered by M. Brown,
C. Trujillo,
D. Rabinowitz
Discovery date November 14, 2003
MPC designation 90377 Sedna
Pronunciation /ˈsɛdnə/ SED-nə
Alternate name(s) 2003 VB12
Minor planet
Trans-Neptunian object
detached object[2]
Epoch September 26, 1990 (JD 2 448 160.5)
Aphelion 1.459 × 1014 m (975.56 AU)
Perihelion 1.139 3 × 1013 m (76.156 AU)
Semi-major axis 7.866 8×1013 m (525.86 AU)
Eccentricity 0.855
Orbital period around 4,404,480 d (12,059.06 a)
Average orbital speed 1.04 km/s
Mean anomaly 357.457°
Inclination 11.934°
Longitude of ascending node 144.514°
Argument of perihelion 311.123°
Physical characteristics
Dimensions 1,200–1,600 km[3]
<1,600 km[4]
Mass 8.3 × 1020–7.0 × 1021 kg[5]
(0.05–0.42 Eris)
Mean density 2.0? g/cm³
Equatorial surface gravity 0.33–0.50 m/s²
Escape velocity 0.62–0.95 km/s
Sidereal rotation
0.42 d (10 h) 1
Albedo 0.16–0.30[3]
Temperature below 33 K
Spectral type (red) B-V=1.24; V-R=0.78[6]
Apparent magnitude 21.1[7]
20.4 (Perihelic)[8]
Absolute magnitude (H) 1.56[9]

90377 Sedna is a trans-Neptunian object and a likely dwarf planet discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. It is currently 88 AU from the Sun,[7] about three times as distant as Neptune. For most of its orbit Sedna is farther from the Sun than any other known dwarf planet candidate.[10]



What came to be known as Sedna was discovered during a survey conducted with the Samuel Oschin telescope at Palomar Observatory near San Diego, California (USA) using Yale's 160 megapixel Palomar Quest camera and was observed within days on telescopes from Chile, Spain, and the USA (Arizona, and Hawaii). NASA's orbiting Spitzer Space Telescope was later pointed toward the object, putting an upper-bound on its diameter at roughly three-quarters that of Pluto (less than 1,600 km).[4]

The object is named after Sedna, the Inuit goddess of the sea, who was believed to live in the cold depths of the Arctic Ocean. Before Sedna was officially named it had provisional designation 2003 VB12.


Sedna has a highly elliptical orbit, with its aphelion estimated at 975 AU and its perihelion at about 76.16 AU. At its discovery it was approaching perihelion and about 89.6 AU from the Sun. At the time of its discovery it was the most distant object in the solar system yet observed; although the orbits of some objects—like long-period comets—extend farther than that of Sedna, they are basically too dim to be observed except near perihelion. Eris was later detected at 97 AU.

Panels showing the location of Sedna in relation to other astronomical objects.

Sedna's precise orbital period is not yet known, but it is calculated at between 10.5 and 12.0 thousand years. It should reach perihelion in late 2075[2][11] to mid 2076.[8] Sedna will overtake Eris as the farthest known spheroid orbiting the Sun in 2114.[8]


When first discovered, Sedna was believed to have an unusually long rotational period (20 to 50 days). A search was thus made for a natural satellite, the most likely cause for such a long rotation, but investigation by the Hubble Space Telescope in March 2004 observed no such object orbiting the planetoid. New measurements from the MMT telescope suggest a much shorter rotation period, only about 10 hours, rather typical for bodies of its size.[12]

Physical characteristics

Artist's impression of 90377 Sedna.

Sedna has an absolute magnitude (H) of 1.6,[9] and it is estimated to have an albedo of 0.16 to 0.30,[3] thus giving it a diameter between 1,200 and 1,600 km.[3] At the time of its discovery it was the largest object found in the solar system since the discovery of Pluto in 1930. It is now generally believed to be the fifth largest known trans-Neptunian object after Eris, Pluto, Makemake, and Haumea.[3][13] In 2004, the discoverers placed an upper limit of 1,800 kilometers on its diameter,[14] but by 2007 it was revised downward to being less than 1,600 after observations from the Spitzer Space Telescope.[4]

Sedna is so far from the Sun that the temperature never rises above 33 kelvins (−240 °C; −400 °F).

Observations from Chile show that Sedna is one of the reddest objects in the solar system, nearly as red as Mars. Unlike Pluto and Charon, Sedna appears to have very little methane ice or water ice on its surface; Chad Trujillo and his colleagues at the Gemini Observatory in Hawaii suggest that Sedna's dark red color is caused by a hydrocarbon sludge, or tholin, like that found on 5145 Pholus.[15] Its surface is homogeneous in colour and spectrum; this may be because Sedna, unlike objects nearer the sun, is rarely impacted by other bodies, which would expose bright patches like that on 8405 Asbolus.[16]

Sedna's and Triton's spectra have been recently compared suggesting the following common model of the surface: 24% Triton tholin, 7% amorphous carbon, 26% methanol ice with 33% methane.[17]

Amateur astronomers using advanced software and long exposures have been able to detect Sedna.[18]


The Earth Dysnomia Eris Charon Pluto Makemake Haumea Sedna Orcus 2007 OR10 Quaoar File:EightTNOs.png
Comparison of Eris, Pluto, Makemake, Haumea, Sedna, Orcus, 2007 OR10, Quaoar, and Earth (all to scale).

The discoverers have argued that Sedna is actually the first observed body belonging to the Oort cloud, saying that it is too far out to be considered a scattered disk object. Because it is a great deal closer to the Sun than was expected for an Oort cloud object, and has an inclination roughly in line with the planets and the Kuiper belt, they described the planetoid as being an inner Oort cloud object, situated in the disc reaching from the Kuiper belt to the spherical part of the cloud. By 2006 it was considered a detached object.[19][20]

A number of explanations for Sedna's unusual orbit have been put forward since, including the gravitational influence of a passing star[21][22], Nemesis a hypothetical dim companion to the sun,[23] or a distant, planet-sized object.[24]

Sedna, together with a few other objects (e.g. 2000 CR105), prompted suggestions of a new category of distant objects named extended scattered disc (E-SDO),[25] detached objects,[26] distant detached objects (DDO)[24] or scattered-extended in the formal classification by the Deep Ecliptic Survey.[27]

The last classification, introduces a formal distinction between scattered-near objects (which could be scattered by Neptune) such as Eris from scattered-extended objects like Sedna. The distinction is made formally, using the orbital elements (see Tisserand's parameter).

The discovery of Sedna resurrected the question of which astronomical objects should be considered planets and which should not. On March 15, 2004 articles in the popular press reported that a tenth planet had been discovered. This question was answered under the new International Astronomical Union definition of a planet, adopted on August 24, 2006. It is unknown whether or not Sedna is in hydrostatic equilibrium. If, as currently suspected,[28] it is, then it would qualify as a dwarf planet. Sedna has a Stern–Levison parameter estimated at between 8 × 10−5 and 6 × 10−3 times that of Pluto,[29] and therefore cannot be considered to have cleared the neighborhood of its orbit, even though no other objects have yet been discovered in its vicinity.

Mathematical speculation

A study done by Hal Levison and Alessandro Morbidelli of the Observatoire de la Côte d'Azur (OCA) in Nice, France, suggested that the most likely explanation for Sedna's orbit was that it had been perturbed by a close (~800 AU) pass by another star in the first 100 million years or so of the solar system's existence, possibly one of the other stars that formed out of the same collapsing nebula as the Sun.[21][30] They proposed another scenario, which may explain Sedna's orbit more accurately: Sedna could have formed around a brown dwarf about 20 times less massive than the Sun and have been captured by the solar system when the brown dwarf passed through it.

Rather than within a collapsing nebula or around a brown dwarf, one commonly accepted hypothesis[31] is that our solar system was once within an open cluster which gradually dissociated over time.[31][32] A close neighboring star located within the same stellar cluster and which later moved away then could have dragged Sedna out farther from the Sun to its present orbit.[31]

Another possible explanation, advanced by Gomes, involves perturbations of Sedna's orbit by a hypothetical planetary-sized body in the inner Oort cloud. Recent simulations show that Sedna's orbital characteristics could be explained by perturbations by a Neptune-mass object at 2000 AU (or less), a Jupiter-mass at 5000 AU, or even an Earth-mass object at 1000 AU.[24][31] Another object, 2000 CR105, has an orbit similar to Sedna's but a bit less extreme: perihelion is 44.3 AU, aphelion is 394 AU, and the orbital period is 3240 years. Its orbit may have resulted from the same processes that produced Sedna's orbit.

It has also been proposed that Sedna's orbit is the result of influence by and in resonance with Nemesis, a theorized dim companion to the Sun which has been proposed to be responsible for the periodicity of mass extinctions on Earth from cometary impacts, the lunar impact record, and the common orbital elements of a number of long period comets.[23]

Mission to explore

Sedna's perihelion will be reached within this century, before Sedna moves back out and farther away from the Sun again for another estimated 12 thousand years. Though an exploration target within our solar system,[33] NASA is not considering any type of exploration mission at this time.

See also


  1. ^ "Discovery Circumstances: Numbered Minor Planets (90001)-(95000)". IAU: Minor Planet Center. http://www.cfa.harvard.edu/iau/lists/NumberedMPs090001.html. Retrieved 2008-07-23. 
  2. ^ a b c Buie, Marc W. (2007-08-13). "Orbit Fit and Astrometric record for 90377". Deep Ecliptic Survey. http://www.boulder.swri.edu/~buie/kbo/astrom/90377.html. Retrieved 2006-01-17. 
  3. ^ a b c d e Brown, Michael E.. "The largest Kuiper belt objects" (PDF). CalTech. http://www.gps.caltech.edu/~mbrown/papers/ps/kbochap.pdf. Retrieved 2008-09-19. 
  4. ^ a b c 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. http://arxiv.org/abs/astro-ph/0702538v2. Retrieved 2008-07-27. 
  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". http://www.physics.nau.edu/~tegler/research/survey.htm. Retrieved 2006-11-05. 
  7. ^ a b "AstDys (90377) Sedna Ephemerides". Department of Mathematics, University of Pisa, Italy. http://hamilton.dm.unipi.it/astdys/index.php?pc= Retrieved 2009-03-16. 
  8. ^ a b c "Horizons Output for Sedna 2076/2114". http://home.comcast.net/~kpheider/Sedna2076.txt. Retrieved 2007-11-19.  Horizons
  9. ^ a b "JPL Small-Body Database Browser: 90377 Sedna (2003 VB12)". 2007-11-08 last obs. http://ssd.jpl.nasa.gov/sbdb.cgi?sstr=Sedna. Retrieved 2008-06-11. 
  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. ^ 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. 
  13. ^ 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. 
  14. ^ W. M. Grundy, K. S. Noll, D. C. Stephens. "Diverse Albedos of Small Trans-Neptunian Objects". Lowell Observatory, Space Telescope Science Institute. http://arxiv.org/abs/astro-ph/0502229. Retrieved 2007-03-26. 
  15. ^ McKee, Maggie (2005). "Distant planetoid Sedna gives up more secrets". NewScientist.com news service. http://www.newscientist.com/article.ns?id=dn7272. Retrieved 2005-03-05. 
  16. ^ Alexander, Amir (18 April 2005). "Sedna: Mysterious Planetoid Slowly Yielding Up Its Secrets". The Planetary Society. http://www.planetary.org/news/2005/0418_Sedna_Mysterious_Planetoid_Slowly.html. Retrieved 2006-09-15. 
  17. ^ 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. 
  18. ^ RickJ. "1.5 hour exposure of Sedna (apmag 21) and UGC 2712 (apmag 17)". Bad Astronomy and Universe Today Forum. http://www.bautforum.com/astrophotography/91384-sedna.html#post1540197. Retrieved 2009-08-01. 
  19. ^ 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.
  20. ^ 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.
  21. ^ a b 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)
  22. ^ 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. http://arxiv.org/abs/astro-ph?papernum=0412030. 
  23. ^ a b Staff. "Evidence Mounts For Companion Star To Our Sun." SpaceDaily, April 25, 2006. Accessed November 27, 2009.
  24. ^ a b c Rodney S. Gomes, John J. Matese, and Jack J. Lissauer A Distant Planetary-Mass Solar Companion May Have Produced Distant Detached Objects To appear in Icarus (2006). Preprint
  25. ^ Evidence for an Extended Scattered Disk?
  26. ^ 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)
  27. ^ 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.
  28. ^ Brown, Michael E.. "The Dwarf Planets". California Institute of Technology, Department of Geological Sciences. http://web.gps.caltech.edu/~mbrown/dwarfplanets/. Retrieved 2008-02-16. 
  29. ^ 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
  30. ^ "The Challenge of Sedna". Harvard-Smithsonian Center for Astrophysics. http://www.cfa.harvard.edu/~kenyon/pf/sedna/. Retrieved 2009-03-26. 
  31. ^ a b c d "Transneptunian Object 90377 Sedna (formerly known as 2003 UB313)". The Planetary Society. http://www.planetary.org/explore/topics/our_solar_system/trans_neptunian_objects/sedna.html. Retrieved 2010-01-03. 
  32. ^ Please refer also to Stellar kinematics. Nebulae and star clusters are no longer accepted as one in the same.
  33. ^ "Solar System Exploration: Multimedia: Gallery". NASA. http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=1504. Retrieved 2010-01-03. 


External links


Simple English

[[File:|thumb|right|What 90377 Sedna may look like.]]

File:Oort cloud Sedna
Image showing 90377 Sedna's Orbit. Moving anti-clockwise from Upper Left, the images are of: The orbits of Inner Planets including Asteroid Belt and Jupiter; The Solar System showing the Solar System known before 90377 Sedna was discovered with 90377 Sedna well outside orbits of Neptune and Pluto and even outside Kuiper Belt; The full orbit of Sedna; and the inner extent of Oort Cloud, showing that even this large, elliptical orbit is well outside of Oort Clouds inner extent.

90377 Sedna (or simply just Sedna) is classified as a scattered object, but it is debatable that it is actually a dwarf planet. When it was discovered in 2003 by Mike Brown, Chad Trujillo and David Rabinowitz, it was said to be the tenth planet. However, due to Pluto no longer being classified as a planet, it is now classified as a dwarf planet like Pluto. It takes 90377 Sedna 10,500 years to fully orbit the Sun. No pictures can be taken of Sedna because very little light from the sun reaches it. For this reason, Sedna has been known as "Cobian", meaning shadows in ancient Greek. Due to its orbit, the chances of this object being found was .017%. Hypothetically, 40- 120 more objects this size should exist without our knowledge. 90377 Sedna will complete its ~12,000 year orbit within this century; however, NASA is not planning on any mission to explore it.


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