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August 24

An artist's conception of Pluto based on Hubble Space Telescope images An artist's conception of Pluto based on Hubble Space Telescope images
Image Credit: C.M. Handler [CC-BY-SA-3.0 or GFDL], via Wikimedia Commons

Today in Science

Pluto Demoted

On this day in 2006, the International Astronomical Union demoted Pluto, discovered in 1930, from being the ninth planet in our solar system.

Pluto, with its erratic, angled orbit, was renamed a dwarf planet, instead.

 At that time, new guidelines were drawn up to define a planet in our solar system:

  1. It must orbit the sun.
  2. It must have gravity strong enough to maintain a roughly spherical shape.
  3. It must have cleared other large objects out of its immediate area, making it the most significant object in its surroundings.

Pluto, Eris, and Ceres, the three dwarf planets, fail to qualify as planets based on that last guideline, since they all can be found in busy sections of space -- Ceres in an asteroid belt and Pluto and Xena amidst the frozen ices of the Kuiper Belt. Makemake and Haumea, also located in the Kuiper Belt, were later added as dwarf planets in 2008. Others potential dwarf planets are awaiting confirmation of their status.

 Check out these resources from Science NetLinks on our solar system:


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