90377 Sedna ne mai girma karamin duniya a cikin m kai na Solar System cewa shi ne, kamar yadda na 2015, a wani nisa na game da 86 astronomical raka'a (1.29 × 10 km; 8.0 × 109 mi) daga Sun, game da sau uku kamar yadda nisa kamar yadda Neptune. Spectroscopy ya bayyana cewa Sedna ta surface abun da ke ciki shi ne kama da wadanda na wasu sauran trans-Neptunian abubuwa, kasancewa da yawa a cakuda ruwa, methane, da kuma nitrogen kankara da tholins. Its surface ne daya daga cikin reddest tsakanin Solar System abubuwa. Yana da mafi kusantar zama wani dwarf duniya. Daga cikin takwas mafi girma trans-Neptunian abubuwa, Sedna ne kawai wanda ba a sani a yi wata. Ga mafi yawan, shi ne ko da nisa daga Sun a halin yanzu, tare da aphelion a 9371 AU.
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