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
[...] This item, believe it or not, was the lead story this morning on many news networks. Yep, just last week I was talking about the solar system expanding to 12 planets, well now it’s down to 8. Pluto, an odd-ball planet if there ever was one, has been declassified as a planet. It’s now in a class called “Plutons” and is one of many objects in it’s general neighborhood. Beyond the fact that Pluto isn’t as unique as it was once thought (something required, I guess for planetary status), it’s orbit overlaps Neptune and that was the last straw (Neptune to Sun: Mom! Pluto won’t stay on his side of the ecliptic!). Here’s a quote I pulled from CNN: Instead, it will be reclassified in a new category of “dwarf planets,” similar to what long have been termed “minor planets.” The definition also lays out a third class of lesser objects that orbit the sun — “small solar system bodies,” a term that will apply to numerous asteroids, comets and other natural satellites. Source: CNN.com – Pluto gets the boot – Aug 24, 2006 [...]