Meet the Solar System's Dwarf Planets | Pluto, Eris, Ceres & Dwarf Planets | Solar System Exploration & Planet Definition
Artist's impression of Pluto and Charon as seen from one of Pluto's other moons.
CREDIT: David Aguilar/Center for Astrophysics
For three-quarters of a century, schoolkids learned that our solar system has nine planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto.
But things changed nearly five years ago today. On Aug. 24, 2006, the International Astronomical Union (IAU) struck Pluto from the list, demoting it to the newly created category of "dwarf planet." The move was spurred by the discovery of multiple large bodies orbiting even farther from the sun than distant Pluto — particularly an object called Eris, which appeared to be bigger than Pluto.
As a result, the IAU came up with a new definition of "planet": A body that circles the sun without being some other object's satellite, is large enough to be rounded by its own gravity (but not so big that it begins to undergo nuclear fusion, like a [...]
~~~~~~~~~~~~~~~~~
You can follow SPACE.com senior writer Mike Wall on Twitter: @michaeldwall. Follow SPACE.com for the latest in space science and exploration news on Twitter @Spacedotcom and on Facebook.
Comments
Post a Comment