Sedna of the Outer Solar System . ... Credit Copyright: R. Hurt ( SSC-Caltech ), JPL-Caltech , NASA Explanation: What is the most distant known object in our Solar System ? A new answer to this centuries-old question was announced yesterday by NASA with the discovery of a dark red object dubbed Sedna . ... Sedna is estimated to be about three-quarters the size of Pluto and therefore the largest Solar System object found since Pluto in 1930. ... NASA Web Site Statements, Warnings, and Disclaimers . ...