Reply to post: Re: They were correct

YOU! DEGRASSE! It's time to make Pluto a proper planet again, says NASA boffin

Martin
Headmaster

Re: They were correct

The satellites of all planets, if present, rotate around the planet. But Pluto and Charon rotate around one another in a "dumbbell" configuration. Charon doesn't revolve around Pluto any more than Pluto revolves around Charon.

I happen to agree that Pluto shouldn't be a planet. But I don't think the argument that Pluto and Charon rotate around each other is relevant.

Pluto and Charon rotate around the the centre of gravity of the Pluto/Charon system, just like, for example, the Earth and the Moon rotate around the centre of gravity of the Earth/Moon system. Pluto and Charon are much closer in mass to each other that Earth and the Moon, and so the centre of gravity is somewhere between them. In the case of the Earth and the Moon, the centre of gravity is about a thousand miles below the surface of the Earth.

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