Discovery of a candidate inner oort cloud planetoid

Michael E. Brown, Chadwick Trujillo, David Rabinowitz

Research output: Contribution to journalArticlepeer-review

193 Scopus citations


We report the discovery of the minor planet (90377) Sedna, the most distant object ever seen in the solar system. Prediscovery images from 2001, 2002, and 2003 have allowed us to refine the orbit sufficiently to conclude that Sedna is on a highly eccentric orbit that permanently resides well beyond the Kuiper Belt with a semimajor axis of 480 ± 40 AU and a perihelion of 76 ± 4 AU. Such an orbit is unexpected in our current understanding of the solar system but could be the result of scattering by a yet-to-be-discovered planet, perturbation by an anomalously close stellar encounter, or formation of the solar system within a cluster of stars. In all of these cases a significant additional population is likely present, and in the two most likely cases Sedna is best considered a member of the inner Oort Cloud, which then extends to much smaller semimajor axes than previously expected. Continued discovery and orbital characterization of objects in this inner Oort Cloud will verify the genesis of this unexpected population.

Original languageEnglish (US)
Pages (from-to)645-649
Number of pages5
JournalAstrophysical Journal
Issue number1 I
StatePublished - Dec 10 2004
Externally publishedYes


  • Kuiper Belt
  • Oort Cloud
  • Planetary systems: formation
  • Solar system: formation

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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