Planet (Stern and Levison's definition)

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See also planet (astronomy), planet (alternative definition).

Astronomers Alan Stern and Harold Levison proposed in 2000 to define a planet as an object large enough for gravity to give it a round shape but not large enough to be a star ([1]). Thus the following all count as planets in our solar system:

  • the eight (classical) planets recognized by the International Astronomical Union
    • Mercury
    • Venus
    • Earth
    • Mars
    • Jupiter
    • Saturn
    • Uranus
    • Neptune
  • dwarf planets
    • five currently recognized by the IAU
      • Ceres
      • Pluto
      • Haumea
      • Makemake
      • Eris
    • as of 2012, Stern considered more than seven other then known objects to be dwarf planets, and reported an estimate that there might be more than 10,000 ([2]); another astronomer, Mike Brown, maintains a continuously updated ranking list ([3]) of the most likely dwarf planets; as of 7 September 2015, the top 9 not already recognized by the IAU are
      • 2007OR10 (code name for an object not yet given an official name)
      • Quaoar
      • Sedna
      • Orcus
      • 2002MS4
      • Salacia
      • 2003AZ84
      • 2013FY27
      • Varuna
  • "satellite planets", i.e. satellites qualifying as planets under this definition. According to Wikipedia ([4]) there are nineteen of these:
    • orbiting Earth
      • the Moon
    • orbiting Jupiter
      • Io
      • Europa
      • Ganymede
      • Callisto
    • orbiting Saturn
      • Mimas
      • Enceladus
      • Tethys
      • Dione
      • Rhea
      • Titan
      • Iapetus
    • orbiting Uranus
      • Ariel
      • Umbriel
      • Titania
      • Oberon
      • Miranda
    • orbiting Neptune
      • Triton
    • orbiting Pluto
      • Charon