90377 Sedna Totally Explained

Everything about Sedna Planetoid totally explained

| spectral_type= (red) B-V=1.24; V-R=0.78 | magnitude = 20.4 (Perihelic) Sedna will overtake Eris as the furthest known spheroid orbiting the Sun in 2114.
   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. 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 orbital characteristics could be explained by perturbations by a Neptune-mass object at 2,000 AU (or less), a Jupiter-mass at 5,000 AU or even an Earth-mass object at 1,000 AU.
   Another object,, 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 3,240 years. Its orbit may have resulted from the same processes that produced Sedna's orbit.

Physical characteristics

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

Earth rect 646 1714 2142 1994 The Earth
Eris and Dysnomia circle 226 412 16 Dysnomia circle 350 626 197 (136199) Eris
Pluto and Charon circle 1252 684 86 Charon circle 1038 632 188 (134340) Pluto
2005 FY9 circle 1786 614 142 (136472) 2005 FY9
2003 EL61 circle 2438 616 155 (136108) 2003 EL61
Sedna circle 342 1305 137 (90377) Sedna
Orcus circle 1088 1305 114 (90482) Orcus
Quaoar circle 1784 1305 97 (50000) Quaoar
Varuna circle 2420 1305 58 (20000) Varuna

desc none

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Notes:

Details on the new coding for clickable images is here:

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.

Moons should be placed on "top" so that their smaller circles won't disappear "under" their respective primaries. Sedna has an estimated diameter of between 1,180 and 1,800 kilometres (730 to 1,120 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,, and . 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. 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.
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.

Classification

The discoverers have argued that Sedna is actually the first observed body belonging to the Oort cloud, saying that it's too far out to be considered a Scattered disk object. Because it's 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 and a distant, planet-sized object.
   Sedna, together with a few other objects discovered since (for example ), prompted suggestions of a new category of distant objects named Extended scattered disc (E-SDO), detached objects, Distant Detached Objects (DDO) or Scattered-Extended in the formal classification by Deep Ecliptic Survey.
   The last classification, introduces a formal distinction between Scattered-Near objects (which could be scattered by Neptune) for example 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. It is unknown whether or not Sedna is in hydrostatic equilibrium. If, as currently suspected, it is, then it would qualify as a dwarf planet. Sedna has a Stern–Levison parameter estimated at between 8 and 6 times that of Pluto, and therefore can't be considered to have cleared the neighbourhood of its orbit, even though no other objects have yet been discovered in its vicinity.

Further Information

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