Sedna waa meeraha yar ee weyn ee ku yaalla meelaha ka baxsan ee Nidaamka Qorraxda oo ahaa, ilaa 2015, masaafo qiyaastii 86 astronomical units (1.29×10 km; 8.0×109 mi) oo ka socota Qorraxda, qiyaastii saddex jeer sida Neptune. Spectroscopy ayaa shaaca ka qaaday in Sedna's dusha sare uu la mid yahay kuwa qaar ka mid ah walxaha kale ee ka baxsan Neptune, oo inta badan isku dar ah biyaha, methane, iyo barafka nitrogen oo leh tholins.
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