August 16, 2006
Will we soon have 12 planets?
2500 astronomers from 75 nations are currently meeting in Prague to, among other things, hammer out a universal definition of a planet — a debate which has arisen from Pluto’s much-contested status as a planet — and to vote on a proposal to establish that there are 12 planets in our solar system. If the proposal is approved, the order of planets in our system would be Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, and an as-yet-unnamed body known as 2003-UB313.
The Pluto-Charon distinction is particularly interesting I think, because this in effect would be a “binary planet system” (my own term, not theirs). Charon is currently considered a moon of Pluto. However, it is nearly as large as Pluto itself and as such it doesn’t actually orbit Pluto — they sort of orbit each other, much like stars in a binary star system.
Since Pluto was discovered in 1930, there have been nine planets in our solar system. Should the 12-planet proposal be approved, it will have far-reaching effects on schools, teachers, and textbooks which currently describe the nine-planet system.
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