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moon, and "triple" for minor planets with two moons. If one object is much bigger it is referred to as the primary and its companion as the secondary. The term double asteroid is sometimes used for systems in which the asteroid and its moon are roughly the same size, while binary tends to be used independently from the relative sizes of the components. When binary minor planets are similar in size, the Minor Planet Center (MPC) refers to them as "binary companions"

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