Quick, how many planets are there? Don’t answer so fast …
I just heard this on CBC radio and then found it on Forever Geek, that the definition of a planet has now been updated/changed to:
A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet.
So, according to Scientific American:
By these criteria, the sun has 12 planets: the nine conventional ones plus Charon, Xena, and the largest asteroid, Ceres (which has been there before — it was regarded as a planet for a half-century after its discovery). More may soon join them. Astronomers could find that other asteroids such as Vesta have a round shape, and new discoveries of Xena-like bodies are almost guaranteed.
Nine was such a nice number. Oh well. Now I have to find a solar system map to learn where these new planets are.
1 Comment