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I was just wondering if it were possible to A) Orbit the moon and earth B) To orbit any two celestial bodies really?

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up vote 25 down vote accepted

The simple answer is yes.

The more complicated answer starts to look at types of orbit.

  • You could have a figure-8 orbit, which has centres around both.
  • You could have an orbit that goes around the centre of mass of the two bodies (in the case of Earth - Moon this is a point within the Earth, but for Pluto-Charon it lies between the two bodies) - this is likely to be a much wider orbit
  • You could have a Lagrange orbit, where you are orbiting a gravitational point because of the two bodies, but not actually going round them (odd edge case of the word 'orbit')

Some may be stable, others not. In fact the free-return trajectory for Apollo 8, 10 and 11 is an unstable version of the first one. It is a figure-8 that goes out past the moon and comes back. But only once.

Have a read of @TildalWave's post for more info on resonant orbits.

And an example I love - the Apollo 12 fragment (from Wikipedia):

enter image description here

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So in a lagrange orbit it'd be like playing Tug-Of-War with an evenly matched team, keeping the body central? – Josh R Mar 25 at 14:01
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Most orbits of these kinds are not very stable. The earth-moon system had a temporary satellite in an orbit around the center of mass in 2006-2007: en.wikipedia.org/wiki/2006_RH120 – Rob Mar 25 at 15:38
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Fascinating graphic! Where is it from, or how is it made? What is "The" Apollo 11 fragment? Inquiring minds want to know! – uhoh Mar 25 at 17:00
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Note that an object orbiting the Earth needs to be inside the Earth's Hill sphere, or it risks being lost into a solar orbit instead. This means that it can't orbit much further than about 3.88 times farther than the Moon, which might not be a large enough orbit to treat the Earth-Moon system as a point mass concentrated at a single point. – Michael Seifert Mar 25 at 19:38
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Yup. It came as a surprise to astronomers when they figured out what it was. – Rory Alsop Mar 29 at 18:10

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