Wednesday, February 11, 2015

Dwarf Planets: Science and Facts

Pluto was demoted to dwarf planet status in 2006, joining Eris, Haumea, Makemake and Ceres.

Credit: Karl Tate,

In 2006, an assembly of the International Astronomical Union voted to define a planet as a celestial body that a) is in orbit around the sun, 2) has enough mass for its gravity to pull it into a rounded shape (hydrostatic equilibrium), and 3) has cleared the neighborhood of its orbit of other, smaller objects.

This last criterion is the point at which planets and dwarf planets differ. A planet's gravity either attracts or pushes away the smaller bodies that would otherwise intersect its orbit; the gravity of a dwarf planet is not sufficient to make this happen.

Astronomers estimate that there could be as many as 200 dwarf planets in the solar system and Kuiper Belt. But the differences between planets and dwarf planets may not be obvious at first. 

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