12 Planets, Maybe More???

The International Astronomical Union has finally taken up the task of creating an official scientific definition of what constitutes a planet: http://www.msnbc.msn.com/id/14364833/

I’ve been watching astronomers argue about this for the past few years. The debate heated up with the recent discoveries of Sedna and 2003 UB313 (“Xena”) in the outer reaches of the solar system.

The definition gaining the most favor is this:
"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."

Under this plan, not only would Sedna and Xena both be considered planets, but so would the asteroid Ceres, which orbits the Sun in the asteroid belt between Mars and Jupiter. There is also a weird corollary to the definition that means Charon, Pluto’s moon, would also be considered a planet. Since it isn’t technically a satellite of Pluto, it’s part of a “double planet system,” which means Pluto and Charon count separately.

That raises the official tally of planets to 12, and I can think of a few more that might have to be added: Quaoar and (perhaps) Ixion. Both reside in the Kuiper Belt with Sedna and Xena.

I’m just wondering what others think of this: would you like to see the number of planets possibly raised to include as many as 53 objects, or would you rather stick with the “official” 9 planets, even though it’s scientifically arbitrary?

As for myself, I think the definition currently under consideration is about as scientifically sound as it can possibly be. Any other standard sacrifices science for tradition and convenience. If it’s massive enough for gravity to make it round, and it orbits a star, it’s a planet. There might be sub-classifications, like gas giant, dwarf planet, etc., but it’s still a planet.

Here’s a graphic of our “new” solar system:


http://msnbcmedia.msn.com/j/msnbc/Co..._2p.hlarge.jpg

Actually, I think you have 13 then. Charon, Ceres, Sedna and Xena added to the current 9.

A specific definition is needed for clarification and I have no problem with what is proposed. I haven't been paying attention like you but I find astronomy fascinating.

I realized after I posted that Sedna wasn't included in that graphic for some reason...perhaps because its orbit is so odd. It still seems to qualify under the rules the IAU is considering.

Personally, I think adding Charon to the list of planets is stretching it a bit far. Maybe it isn't a satellite of Pluto technically, but it isn't out there on its own, either. Instead of listing Charon seperately, I would rather put a footnote next to Pluto indicating that it's really a double planetary system.

Who said Uranus??? Oh..sorry. Nobody.

Actually I am a bit of an astronomer too and have a 10" dob that I cart around.

Anyone check out www.heavens-above.com?

I wonder how they would classify the two bodies they found recently, which are basically a star and a planet revolving around each other...could the planet be considered to be in orbit of the star?

Pluto is officially NOT a planet. So we now have eight: http://www.timesonline.co.uk/article...327821,00.html

Not so fast...apparently, this has caused major hard feelings among scientists: http://www.msnbc.msn.com/id/15836050/

Quote:

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Before the dust even settled after the Great Pluto War at the International Astronomical Union's General Assembly in Prague, one thing became clear: There will never be an accepted scientific definition for the term "planet."
Rather than crafting an acceptable definition, the IAU alienated members, put the group's authority in jeopardy and fueled schisms among astronomers on theoretical grounds and even nationality.
And the whole affair was scientifically pointless, many astronomers say.

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On top of that, many astronomers weren't even allowed to vote. The article also goes on to explain why defining a planet based on our solar system is inadequate to describe other objects we already know about throughout the galaxy.

There is also a nice picture there of Pluto with its three moons.

Don't forget to count the planet I live on.:D