The Difference Between Asteroids, Comets, and Dwarf Planets

Ceres was discovered in 1801 as the first asteroid. Pluto was discovered in 1930 as the ninth planet in the Solar System. But recently, it was reclassified as a “dwarf planet”. Let’s take a look at how the classification works for asteroids, comets, and dwarf planets:

  • Asteroid – a mostly rocky object that is smaller than a dwarf planet and orbits the Sun. There is a “belt” of asteroids inbetween the orbits of Mars (1.52 AU – from 205m km to 249m km) and Jupiter (5.2 AU – from 741m km to 817m km). The asteroid belt mostly conforms to the plane of the Solar System (the ecliptic plan), but asteroid orbits vary in their inclination by as much as 40 degrees and can be also be elliptic rather than circular. Asteroids are not confined to this belt area; it is simply where we have observed many of them.
  • Comet – an object that is composed of rock, dust, and ice. They often appear “fuzzy” because as a comet approaches the Sun, the ice is melted and then vented as gases, creating a “coma” or tail that glows in the light from the Sun.
  • Dwarf Planet – an object that is large enough for its gravity to have crushed it into a spheroid, but not large enough to have cleared its orbit of other objects, and it is not a satellite (moon) of another object but orbits the Sun directly.

Sizes of Solar System objects smaller than Mars:

  • Ganymede – 5,268 km dia, moon of Jupiter
  • Titan – 5,151 km dia, moon of Saturn
  • Mercury – 4,879 km dia, planet
  • Callisto – 4,821 km dia, moon of Jupiter
  • Io – 3,636 km dia, moon of Jupiter
  • Moon (Luna) – 3,474 km dia, moon of Earth
  • Europa – 3,100 km dia, moon of Jupiter
  • Triton – 2,700 km dia, moon of Neptune
  • Pluto – 2,374 km dia, dwarf planet (formerly a planet)
  • Eris – 2,326 km dia, dwarf planet
  • Titania – 1,578 km dia, moon of Uranus
  • 2007 OR – 1,535 km dia, dwarf planet
  • Rhea – 1,528 km dia, moon of Saturn
  • Oberon – 1,523 km dia, moon of Uranus
  • Iapetus – 1,471 km dia, moon of Saturn
  • Makemake – 1,434 km dia, dwarf planet
  • Huamea – 1,400 km dia, dwarf planet
  • Charon – 1,212 km dia, moon of Pluto
  • Umbriel – 1,170 km dia, moon of Uranus
  • Ariel – 1,158 km dia, moon of Uranus
  • Dione – 1,122 km dia, moon of Saturn
  • Quaoar – 1,070 km dia, dwarf planet
  • Tethys – 1,066 km dia, moon of Saturn
  • Sedna – 1,000 km dia, dwarf planet
  • Ceres – 945 km dia, dwarf planet (formerly an asteroid)
  • 2002 MS4 – 934 km dia, dwarf planet
  • Orcus – 917 km dia, dwarf planet
  • Salacia – 850 km dia, dwarf planet
  • 2013 FY27 – 780 km dia, dwarf planet
  • 2003 AZ84 – 727 km dia, dwarf planet
  • Varuna – 668 km dia, dwarf planet

Comments are closed.