Barring comets

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Barring comets Empty Barring comets

Post by kosovohp on Sun Nov 14, 2010 4:13 am

Barring comets, Sedna has the longest orbital period of any known object in the Solar System, calculated at between 11,800 and 12,100 years.[2] This represents a best-fit solution, as Sedna has only been observed over a brief part of its orbital arc. Its orbit is extremely eccentric, with an aphelion estimated at 960 AU and a perihelion at about 76 AU. At its discovery it was approaching perihelion at 89.6 AU[16] from the Sun, and was the most distant object in the Solar System yet observed. Eris was later detected by the same survey at 97 AU. Although the orbits of some long-period comets extend farther than that of Sedna, they are too dim to be discovered except when approaching perihelion in the inner Solar System. Even as Sedna nears its perihelion in late 2075[c] to mid 2076,[9] the Sun would appear merely as a bright star in its sky: with an angular diameter too small to resolve as a disc, it would be only 100 times brighter than a full Moon on Earth.[17]
When first discovered, Sedna was believed to have an unusually long rotational period (20 to 50 days).[17] It was initially speculated that Sedna's rotation was slowed by the gravitational pull of a large binary companion, similar to Pluto's moon Charon.[12] A search for such a satellite by the Hubble Space Telescope in March 2004 found nothing,[18][e] and subsequent measurements from the MMT telescope suggest a much shorter rotation period, only about 10 hours, rather typical for bodies of its size.[19]

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