If a planet has to "clear the neighborhood around its orbit," does that mean there can be no binary planets??

Question

For example, what if Jupiter and Saturn orbited each other, while orbiting the sun - like Pluto and Charon? Then would they be stripped of planethood as well? Also, the requirement to orbit the sun means there can't be any extrasolar planets!

OK so to clarify: satellites all ready have an explicit definition. The moon is a satellite of earth because the center of gravity of the two bodies lies below the surface of the earth. So moons don't count towards the clearing part. But binary stars orbit each other and have a center of mass between the two stars, so I am wondering if the new definition of a planet (dictionary.com's is now obsolete!) is overlooking the possibility of a binary planet, since the neighborhood wouldn't be cleared?

Answer 1

That's exactly what it means. They would have to come up with a new term for a binary planet.

If the Earth were denser and smaller, or the moon further away, the barycenter for the system would be outside the earth. Therefore, we'd be a binary planetary system or two dwarf planets.

Answer 2

Technically, Pluto doesn't orbit Charon, but vice versa is true. And I don't know much about binary planets, so I won't say anything.

–noun 1. Astronomy. a. Also called major planet. any of the nine large heavenly bodies revolving about the sun and shining by reflected light: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, or Pluto in the order of their proximity to the sun.
b. a similar body revolving about a star other than the sun.
c. (formerly) a celestial body moving in the sky, as distinguished from a fixed star, applied also to the sun and moon.

This is from dictionary.com definition for planet, and by sense b, there can be extrasolar planets. :-)

Answer 3

Apparently, that's what they mean, since Pluto's problem (in the news story I read, anyway), was that it crosses Neptune's path.
Another thing: how close to the planet is the neighborhood around its orbit? because most planets have moons, and several (like Saturn) have rings which are chunks of rock and ice.

Good point about the requirement to orbit the sun! I hadn't thought of that!

Answer 4

Or could it also be said that any "planet" hasn't cleared it's neighborhood around its orbit if it has a satellite orbiting it. Would that bring us down to just Mercury and Venus being planets?

Answer 5

God might not play dice but I bet he plays pool. Something will disrupt this delicate balance and we'll be calling them something else then. Call them whatever you want for now as long as they stay where they are.