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RE: Sedna

New Solar Object!. The most distant object orbiting the sun has been detected. Its about 1/3 the size of the earth, 3 billion kilometres further away from the Sun than Pluto. This object has been provisionally named "Sedna", after the Inuit goddess of the sea. Measurements suggest that Sedna has a diameter between 1,180 to 2,360km in diameter and is a half-rock and half-ice mixture.
This would make it the biggest find in the solar system since Pluto was discovered 74 years ago.

An official
spacer.gif Sedna


NASA announcement was made at 1800 UTC 15th March 2004.

It was discovered by astronomers using the 48-inch Samuel Oschin Telescope at California's Mount Palomar Observatory on November 14, 2003.
The Spitzer Space Telescope and the Tanagra Observatories made follow-up studies. Although Sedna could be a so-called Kuiper Belt object, its discoverers are unsure if it is as they consider it unlike any other object yet found.
The importance of Sedna is that it is the first such world discovered in a `normal` orbit. Other similar but smaller worlds, like Quaoar and Varuna, originated in the Kuiper Belt but have since been perturbed into different orbits. The discovery will reignite the debate about what is a planet.
Sedna, or 2003 VB16, as it was originally designated, will have follow-up studies to measure its thermal radiation to determine how hot it is, and therefore provide a better estimate of its size. The planetoid is usually cold; the temperatures never rise above minus 240 degrees Celsius.
There is indirect evidence that Sedna may have a moon; it seems to rotates very slowly, once every approximately 40 days...(now proven not to be the case; the rotation is 10.273+/-0.003 hours, Which is consistent with typical rotation periods of solar system objects, thus obviating the need for a massive companion to slow its rotation. )
A notable feature of Sedna is its reddish colour and it`s very shiny.
. It is currently 13 billion kilometres away, in the Constellation Cetus Position J2000: RA: 3h15m10s Dec: +5d38m15s), and over the next 72 years it will become brighter and closer, after which it will head out into the oort cloud again, reaching 130 billion kilometres from the Sun, taking 10,500-years for one solar orbit.

ORBIT new pictures







2003 VB12






q: perihelion distance (AU)
Q: aphelion distance (AU)
H: absolute visual magnitude
i: inclination of orbit
e: eccentricity of orbit

"Sedna is the Inuit goddess of the sea who was originally a woman thrown into icy Arctic waters by her father. He was attempting to appease another god who had tricked Sedna into marrying him and from whom she was fleeing. When she tried to get back into the boat, her father beat her frozen hands, which when they broke off, turned into whales and other large mammals. While she sank, she did not die but became the goddess of the sea."

Computer simulations
spacer.gif Computer simulations

Computer simulations

show a close encounter with a passing star about 4 billion years ago may have given our solar system its abrupt edge and put small, alien worlds into distant orbits around our sun.
This may explain Sedna`s highly elongated orbits.

They have also identified another Kuiper Belt Object, 2000 CR105, that is the most likely solar system member to have been captured from a passing star, based on the highly elliptical and inclined orbit
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The relative reflectance spectrum of Sedna
spacer.gif reflectance spectrum

Reflectance spectrum

(black circles) and the spectrum of the background sky (grey circles). Gray curves are the model 3 upper limits to the surface fraction of water ice (smooth gray line) and methane ice (jagged gray line). Surface fractions that cause more absorption than the indicated lines are ruled out by observations at the 3 level. Spectrum error bars are computed from the reproducibility of the spectral data in each spectral point.
Because it is so isolated and remote, a lack of collisions and impacts might explain Sedna's red ice-free surface.
Sedna, is probably made up of an equal mixture of ice and rock, and covered with a metre or so of hydrocarbon sludge. This sludge is produced when the Sun's ultraviolet radiation and charged particles alter the chemical bonds between atoms in the ice.
"You just get this big tangle of carbon and hydrogen bonds, which turns the surface dark like asphalt or tar - Chad Trujillo, researcher at the Gemini Observatory.
A similar "space weathering" process occurs on the 190-kilometre-wide minor planet 5145, called Pholus, which lies near Saturn and is also very red.
Astronomers have new evidence
spacer.gif 2002 AW197

2002 AW197

that KBOs (Kuiper Belt Objects) are smaller than previously thought. KBOs - icy cousins to asteroids and the source of some comets - are the leftover building blocks of the outer planets. Astronomers using the worlds most powerful telescopes have discovered about 1,000 of these objects orbiting beyond Neptune since discovering the first one in 1992. Many astronomers had assumed that KBO albedos - like comet albedos - are around four percent and have used that number to calculate KBO diameters. However, early results from the Spitzer Space Telescope survey of 30 Kuiper Belt Objects, astronomers found that a distant KBO designated 2002 AW197 reflects 18 % of its incident light and is about 700 kilometres in diameter; considerably smaller and more reflective than expected.
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-- Edited by Blobrana at 16:56, 2008-01-02



Posts: 131433

The object designated 2003 VB12 was discovered with the Palomar 1.2-m Schmidt telescope on November 14, 2003 and has also been found on sky photographs taken in 2001 and 2002. Orbit computations show that the object's distance from the Sun varies between 76 and about 900 Astronomical Units. Its current distance is about 86 AU, about twice Pluto's distance. A very uncertain diameter of around 1800 km has been estimated from the brightness of the object.

Since the object appears to be somewhat smaller than Pluto and has an extremely elongated orbit with a period of around 10,000 years, compared to 248 years for Pluto, The International Astronomical Union has deemed it appropriate to designate the object as an asteroid and not as the 10th planet.

The name Sedna was proposed after an Inuit ocean goddess, but the name has not yet been endorsed by the IAU and needs to be reviewed first by the IAU Committee on Small Bodies Nomenclature.

Source IAU

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