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apastron(əpăs`trən): see apsisapsis
(pl. apsides), point in the orbit of a body where the body is neither approaching nor receding from another body about which it revolves. Any elliptical orbit has two apsides.
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apastron(ap-ass -tron) See periastron.
That point of the orbit of one member of a binary star system at which the stars are farthest apart.