Have you seen that story on the news about how there is now twelve planets in our solar system? Please read...

Question

Well, there are now 12 planets. They are saying that one of the new ones is Charon (Pluto's moon). If Charon is a moon, then how can it be a planet?

Answer 1

The idea is that Charon and Pluto both orbit around each other, so both should be considered planets. That is different from Earth's moon, which orbits around Earth.

Also part of the idea is that if Pluto is a planet, then other objects just as big as Pluto should be planets. Or maybe it was a mistake to call Pluto a planet. So there should either be 8 planets or 12, but not the current 9.

Answer 2

There are three considerations that are going into whether a body is a 'planet' or not.

The first is gravity. I think the current recommandation is that it have at least a 12000th the mass of the Earth. The presumption is that with this amount of mass, its gravity would force it into a sperical shape. This exclude most asteroids, comets, and other space junk. Things of that size are pretty well known until you start getting way out there... most of the new 'planets' have been known for some time.

The second consideration is that it must orbit the sun. That's not hard - LOTS of stuff is in orbit around the sun. This is mitigated to a large degree by the third consideration.

This third consideration is that it must not be a moon of something else which is considered a planet. Which leads to the question of what, exactly, a moon is... fortunately this question is much less disputed. Object B is a moon of object A if the center of mass between the two lies INSIDE object A. This makes a certain sense - in the most extreme opposite, the center of mass is right between the two objects and the rotate around a common point.

This last consideration is what's producing some of the more controversial results. Jupiter has moons which are around the mass of Earth, but owing to its incredible mass and size, they still count as moons. Pluto is smaller than Earth's moon. The object which was considered by some to be it's moon is smaller yet. But the center of mass between Pluto and Charon is hundreds of miles ABOVE Pluto's surface. They are a double planet and always have been.

Hope that helps. We'll undoubtedly have far more than twelve planets once the entire Kuiper Belt is explored... already there are at least twelve more objects that may qualify as planets under what may become the new definition!

Answer 3

Pluto and Charon are so close to each other in size, they have a relationship unlike any other in the Solar System. So the International Astronomical Union is considering classifying them as part of a "double planet" system.

Hope that helps!

JIM

Answer 4

the whole thing is rediculous...they havent made it official..some scientists want to not make pluto a planet just becuase it is small. It still revolves around the sun. I highly doubt that charon will become a planet.

Answer 5

Is Charon orbiting around pluto, then its a moon, otherwise unless it's actually orbiting around the sun, then it's a planet.

Answer 6

it can't.

The debate is coming about because the definition of a planet is being debated as the definition has never really been scientifically defined.

The 3 new planets are 2 moons of Pluto and an asteroid.

Also, when it comes to space, nothing will ever be settled.

It is infinite and infinitely changing.

Answer 7

Actually, there are more planets than that...the scientific community is voting whether or not to include those planets in text books...

Answer 8

It is categorized as a "double planet"

Answer 9

What about Chiron?