Assertion: andromeda's star | /r/CapableOf | orbit around their common center of mass
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Source sentences:
text: When we think of planets we are used to the idea of planets around the sun in a single star system but in fact a surprising number (about one in two) of the stars we see in the night sky are really multiple star systems; that is, a group of two or more stars orbiting around their common center of mass (they appear as single points of light because of sheer distance).