See also: Sedna

(90377) Sedna ( female name ) is an object of the Solar system of approximately 1  500 kilometers diameter, orbiting at long distance from the Sun. She was discovered by Michael (Mike) E. Brown (Caltech), Chadwick (Chad) A. Trujillo (Gemini observatory) and David L. Rabinowitz (Université Yale) the November 14th 2003. The discovery was announced the March 15th 2004. Revealed with the Telescope Samuel Oschin of the Mount Palomar in California, its existence was confirmed the following days by many teams. The Space telescope Spitzer was also pointed in its direction but did not detect anything; that makes it possible to put a limit upper than the size of Sedna.

One in the beginning had measured one period of rotation supplements very slow object (20 or 40 days), which let think that the rotation of Sedna had was slowed down by a gravitational transfer of energy to a satellite, comparable with the situation of the couple Ground - the Moon. The Space telescope Hubble had then been pointed in its direction in order to seek the possible moon, without success. In April 2005 a more precise measurement of the star made it possible to determine one period of rotation of approximately 10 hours.

At the time of its discovery, Sedna was the largest object discovered in the solar system since the discovery of Pluton. Since, however, larger objects (dwarf planets) were discovered, such as for example (136199) Éris.

Weaker reason than Éris, Sedna played a part in the awakening of the astronomers of the urgency of a clear definition of a planet. Thus Sedna paradoxically contributed to the new definition which brought back planets of the solar system to eight, whereas itself was sometimes called to it tenth planet (before Éris, that one called Xéna at the time, does not charm this false title to him).

Characteristics

Sedna has a diameter ranging between 1  180 and 1  800 kilometers. Further away from the Sun than the couple Pluto - Charon, it has a very elliptic orbit. Its Aphélie is with approximately 942 ua Sun, its Périhélie, which it should reach in 2076, is estimated at 76 ua. It carries out a revolution in 11  486 years.

The scientists estimate that its distance prevents its temperature of surface from rising above -240 °C; moreover, it is about the reddest object of the Solar system after Mars, which is atypical (but frequent at the transneptuniens).

Type of object

Even if its size prevents from qualifying this object of planet, its classification is not obvious (it remains candidate with the new statute of dwarf Planet). Its discoverers estimate that it does not form part of the Ceinture of Kuiper but would be perhaps the first object of the Nuage of discovered Oort, although this one is much more remote; other scientists dispute this vision of the things. Indeed, according to David C. Jewitt, discoverer of the first Asteroid of the Belt of Kuiper, the following possibilities are to be considered:

• Sedna is an object of the Ceinture of Kuiper. For a few years, the scientists have observed the rarefaction of the number of objects of the Ceinture of Kuiper beyond 47 ua. While being moved away much more, even with its Perihelion, it is thus not easy to regard it as such an object. In fact, Sedna never penetrates the zone considered today as the Ceinture of Kuiper.

• Sedna is an object of the Nuage of Oort. David C. Jewitt excludes this assumption: indeed, the Nuage of Oort is much more remote (at least 10  000 ua). Moreover, these objects can have very tilted orbits compared to the plan of the ecliptic (until 180°). Sedna with its 23° of slope, and its proximity with the Sun, is not appropriate.

• For David C. Jewitt, Sedna, with discovered a few years earlier, are the “emerged part of the iceberg” of a new class of objects evolving/moving between the Ceinture of Kuiper and the Nuage of Oort. No particular name was advanced for this new type of object.

Formation

According to David C. Jewitt, Sedna could not be formed where it is: the disc protoplanétaire was too thin at this place to generate an object of this size. According to the scientist, Sedna was formed either in the Ceinture of Kuiper, or in the area of planets. It is later that its aphelion was ejected and, finally, it is probably another gravitational interaction which would have moved its perihelion out of the orbit of Neptune. Besides that starts again the speculations on a obscure companion with our sun which would belong to a binary system.

Name

Owing to the fact that this object is cold and very far away from the Sun, Michael E. Brown had proposed with the international astronomical Union the name Sedna , a goddess Inuit of the ice, which is supposed to live in the depths of the Arctic Ocean. It had to be waited until the elements of its orbit are specified before (its provisional designation) is numbered (90377) and is baptized, which was made in September 2004.

External bonds

• Given '' Minor Planet Center '' on (90377) Sedna
• Page of Michael Brown on (90377) Sedna
• Astrofiles: Sedna
• Article announcing the discovery of the object on futura-sciences.com
• Sedna - pioneer-astro
• '' a revolution-flash '', in connection with the confirmation of the absence of the moon around the object

Be-X-old: Сэдна