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| Credit for image: Dr Alex Harrison Parker supporting NASA |
I for one, am looking forward to the viewing the closest images ever seen of these distant and cold worlds at the edge of our solar system.
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| Images of Pluto and its moon Charon moving around the binary system's common centre of gravity, captured by the space-craft in July 2014 using its best telescopic camera Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute |
Pluto and Charon are a very long way away and very small. Pluto has a diameter roughly two thirds of our Moon and a mass less than 0.24% of Earth. Charon is even smaller at roughly half Pluto's size. However, in terms of relative size, Charon compared with Pluto is the largest known moon in the solar system. The common point of gravity about which both move is therefore somewhere in space between the two bodies but closer to the larger body of Pluto. In the above movie clip you can clearly see that as Charon revolves, so does Pluto. The physics of gravity in action, how brilliant is that!
Our Earth is also part of a binary system with our Moon but because our Moon has a mass significantly lower than that of Earth, the common point of gravity about which both revolve remains inside the Earth's crust . It is however, not located at the Earth's centre but displaced towards the Moon along a line that runs between the Earths centre of mass and the Moon's centre of mass . So in a sense the Moon does not revolve about the Earth!
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