90377 Sedna

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90377 Sedna
Image:Sedna-NASA.JPG
Sedna is located in the center of the green circle
Discovery
Discovered by: M. Brown,
C. Trujillo,
D. Rabinowitz
Discovery date: November 14, 2003
Orbital characteristics[1]
Epoch September 26, 1990 (JD 2448160.5)
Aphelion1.459×1014 m (975.56 AU)
Perihelion: 1.1393×1013 m (76.156 AU)
Semi-major axis: 7.8668×1013 m (525.86 AU)
Eccentricity: 0.855
Orbital period: around 4404480 d (12059.06 a)
Avg. 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: 1180–1800 km
Mass: 1.7-6.1×1021 kg
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 period: 0.42 d (10 h) 1
Albedo: >0.2?
Temperature: below 33 K
Spectral type: (red) B-V=1.24; V-R=0.78 [2]
Apparent magnitude: 20.4 (Perihelic)[3]
Absolute magnitude: 1.6

90377 Sedna (pronounced /ˈsɛdnə/ sed'-nə) is a trans-Neptunian object, discovered by Michael Brown (Caltech), Chad Trujillo (Gemini Observatory) and David Rabinowitz (Yale University) on November 14, 2003. At the time of its discovery it was the most distant observed natural solar system body. Sedna will qualify as a dwarf planet if it proves to be in hydrostatic equilibrium, as currently suspected.

Contents

[edit] General information

Image:Nasa sedna art.jpg
Artist's impression of 90377 Sedna. Courtesy of NASA

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 also pointed toward the object, but could not detect it – putting an upper-bound on its diameter at roughly three-quarters that of Pluto.

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.

[edit] Orbital characteristics

Image:Oort cloud Sedna orbit.jpg
Panels showing the location of Sedna in relation to other astronomical objects. Image courtesy of NASA / JPL-Caltech / R. Hurt

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 at about 90 AU from the Sun. It was the farthest from the Sun that any solar system object had up to then been observed, although some objects like long-period comets originally observed at closer distances were most likely further from the Sun than Sedna but too dim to be observed. Eris was later detected at 97 AU.

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[4][1] to mid 2076.[3] Sedna will overtake Eris as the furthest known spheroid orbiting the Sun in 2114.[3]

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.[5]

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.[6] They proposed another, less probable scenario that managed to explain Sedna's orbit very well —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.

Another possible explanation, advanced by Gomes, involves perturbations of Sedna's orbit by a hypothetical distant ‘planet’ (a planetary-sized companion in the inner Oort cloud). Recent simulations show that Sedna's orbit characteristics could be explained by perturbations by a Neptune-mass object at 2000 AU (or less), a Jupiter-mass at 5000AU or even an Earth-mass object at 1000AU.[7]

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.

[edit] Physical characteristics

<imagemap> Image:EightTNOs.png|thumb|410px|left|Sedna compared with Eris, Pluto, (136472) 2005 FY9, (136108) 2003 EL61, Varuna, Orcus, Quaoar, and Earth.

  1. Earth

rect 646 1714 2142 1994 The Earth

  1. Eris and Dysnomia

circle 226 412 16 Dysnomia circle 350 626 197 (136199) Eris

  1. Pluto and Charon

circle 1252 684 86 Charon circle 1038 632 188 (134340) Pluto

  1. 2005 FY9

circle 1786 614 142 (136472) 2005 FY9

  1. 2003 EL61

circle 2438 616 155 (136108) 2003 EL61

  1. Sedna

circle 342 1305 137 (90377) Sedna

  1. Orcus

circle 1088 1305 114 (90482) Orcus

  1. Quaoar

circle 1784 1305 97 (50000) Quaoar

  1. Varuna

circle 2420 1305 58 (20000) Varuna

desc none

  1. - setting this to "bottom-right" will display a (rather large) icon linking to the graphic, if desired
  1. Notes:
  2. Details on the new coding for clickable images is here: mw:Extension:ImageMap
  3. While it may look strange, it's important to keep the codes for a particular system in order. The clickable coding treats the first object created in an area as the one on top.
  4. Moons should be placed on "top" so that their smaller circles won't disappear "under" their respective primaries.

</imagemap> Sedna has an estimated diameter of between 1180 and 1800 kilometres (730 to 1120 miles). At the time of its discovery it was the largest object found in the solar system since Pluto was discovered in 1930. It is now generally believed to be the 5th largest known trans-Neptunian object after Eris, Pluto, 2005 FY9, and 2003 EL61. Sedna is so far from the Sun that the temperature never rises above 33 kelvin (−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.[8] Its surface is homogeneous in colour and spectrum; this is probably because Sedna, unlike objects nearer the sun, is rarely impacted by other bodies, which would expose bright patches like that on 8405 Asbolus.[9]

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.[10]

[edit] Classification

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 Kuiper belt 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.

A number of explanations have been put forward since, including a passing star[6][11] and a distant, planet-sized object.[7]

Sedna, together with a few other objects discovered since (e.g. 2000 CR105), prompted suggestions of a new category of distant objects named Extended scattered disc (E-SDO),[12] detached objects,[13] Distant Detached Objects (DDO)[7] or Scattered-Extended in the formal classification by Deep Ecliptic Survey.[14]

The last classification, introduces a formal distinction between Scattered-Near objects (which could be scattered by Neptune) e.g. 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 "the tenth planet has been discovered". This question was answered under the new International Astronomical Union definition of a planet, adopted on August 24, 2006. Sedna may be made a candidate for consideration as a dwarf planet. It is not, however, considered to be a planet.

[edit] See also

[edit] References

  1. ^ a b Marc W. Buie (2007-08-13). Orbit Fit and Astrometric record for 90377. Deep Ecliptic Survey. Retrieved on 2006-01-17.
  2. ^ Tegler, Stephen C. (2006-01-26). Kuiper Belt Object Magnitudes and Surface Colors. Retrieved on 2006-11-05.
  3. ^ a b c Horizons Output for Sedna 2076/2114. Retrieved on 2007-11-19. Horizons
  4. ^ Lowell DES Perihelion Epoch = 2000.0 + (2479283.2236 − 2451545.0)/365.25 = 2075.9431 = (2076-1-1 - 20.7768 days) = 2075-12-11
  5. ^ 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.
  6. ^ a b Alessandro Morbidelli and Harold F. Levison Scenarios for the Origin of the Orbits of the Trans-Neptunian Objects 2000 CR105 and 2003 VB12 (Sedna) The Astronomical Journal, (2004) 128, pp 2564-2576. Preprint
  7. ^ a b c 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.
  8. ^ McKee, Maggie (2005). Distant planetoid Sedna gives up more secrets. NewScientist.com news service. Retrieved on 2005-03-05.
  9. ^ Alexander, Amir (18 April 2005). Sedna: Mysterious Planetoid Slowly Yielding Up Its Secrets. The Planetary Society. Retrieved on 2006-09-15.
  10. ^ M. A. Barucci, 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.
  11. ^ 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.
  12. ^ Evidence for an Extended Scattered Disk?
  13. ^ D.Jewitt, 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)
  14. ^ J. L. Elliot, 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.

[edit] Bibliography

[edit] External links

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Sedna


Minor planets
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Scattered disc:2002 TC302  · Eris  · 2004 XR190  · Sedna
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For a complete listing, see List of asteroids. See also Pronunciation of asteroid names and Meanings of asteroid names.
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<imagemap>

Image:Solar System XXVII.png

  1. The Sun

circle 0 0 90 35 The Sun

  1. Mercury

circle 112 18 6 Mercury

  1. Venus

circle 153 18 8 Venus

  1. Earth and the Moon

circle 203 8 4 The Moon circle 194 18 8 Earth

  1. Mars and satellites

circle 239 13 3 Phobos and Deimos circle 233 18 8 Mars

  1. Ceres and the asteroid belt
  2. - by placing the rectangle code for the asteroid belt AFTER Ceres, Ceres is "on top" (and can co-exist)

circle 271 18 8 Ceres rect 256 0 288 35 The asteroid belt

  1. Jupiter and satellites

circle 316 18 15 Jupiter circle 329 5 6 Moons of Jupiter

  1. Saturn and satellites

circle 372 18 10 Saturn circle 381 7 6 Moons of Saturn

  1. Uranus and satellites

circle 418 18 9 Uranus circle 427 10 6 Moons of Uranus

  1. Neptune and satellites

circle 471 10 3 Moons of Neptune circle 462 18 12 Neptune

  1. Pluto, satellites, and the Kuiper belt
  2. - by placing the rectangle code for the Kuiper belt AFTER Pluto, Pluto is "on top" (and can co-exist)

circle 508 13 3 Moons of Pluto circle 504 18 8 Pluto rect 492 0 527 35 The Kuiper Belt

  1. Eris, Dysnomia, and the Scattered disc
  2. - by placing the rectangle code for the Scattered disc AFTER Eris, Eris is "on top" (and can co-exist)

circle 544 14 3 Dysnomia circle 540 18 8 Eris rect 528 0 567 35 The Scattered Disc rect 568 0 597 35 The Oort Cloud

desc none

  1. - setting this to "bottom-right" will display a (rather large) icon linking to the graphic, if desired
  1. Notes:
  2. Details on the new coding for clickable images is here: [1]
  3. The smaller planets have a bit of an overlap just to ensure they're locatable, especially in the belts.
  4. While it may look strange, it's important to keep the codes for a particular system in order. The clickable coding treats the first object created in an area as the one on top.
  5. - I've placed moons on "top" so that their smaller circles won't disappear "under" their respective planets or dwarf planets.
  6. The "poly" code would be more appropriate for the moons of Jupiter, Saturn, and Uranus. However, there appears to be a bug with that aspect of the code.
  7. - I've compensated by using oversized circles for those moon groups, and tucking them UNDER their planets for now.
  8. The Sun is a rectangle as that approximates the edge closely enough for the purposes of this template.
  9. I've guessed as to the boundaries for the KB, SD, and OC - if they need adjustment, load the image into Paint and use the pencil tool to find the appropriate coordinates.

</imagemap>

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ar:سيدنا

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