[uh-pas-truh n, -tron]
noun, plural ap·as·tra [uh-pas-truh] /əˈpæs trə/. Astronomy.
  1. the point at which the stars of a binary system are farthest apart (opposed to periastron).

Origin of apastron

< New Latin < Greek ap- ap-2 + ástron star, constellation; on the model of apogee
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apastron in Science


  1. The point at which an object, such as a planet or comet, is farthest from the center of mass of the star it is orbiting. Compare periastron.
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