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How large does an object need to be for something to orbit it?

The Earth currently has over 2,000 man-made satellites in orbit.

Asked by: Vicky Robson, Leeds

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There is no magic size or mass required for an object in order to have a ‘satellite’. An ‘orbit’ occurs when the gravitational pull from a nearby object exactly matches the forward motion or momentum of the orbiting body. All objects (with mass) have gravity, however small they are. So, theoretically, any object can have another object in orbit around it; as long as that object moves slowly enough to be ‘captured’ by the gravitational pull. Of course, this is unlikely unless these objects are both moving extremely slowly, are close to each other, and are completely isolated from all other forces.


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