90377 Sedna 90377 Sedna /naɪn oʊ ˈθri sevən seˈdnɑ/

noun

1. A planetoid of rock and ice about three-quarters the size of Pluto discovered in 2003; the most distant object known to orbit around the sun  ( Sedna , 90377 Sedna )
   a planetoid of rock and ice about three-quarters the size of Pluto discovered in 2003; the most distant object known to orbit around the sun