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[per-ee-as-truh n, -tron] /ˌpɛr iˈæs trən, -trɒn/
noun, plural periastra
[per-ee-as-truh] /ˌpɛr iˈæs trə/ (Show IPA).
the point at which the stars of a binary system are closest (opposed to apastron).
Origin of periastron
1850-55; < peri- + Greek ástron star; modeled on perihelion
Related forms
periastral, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the Web for periastron
Historical Examples
  • At least, the periastron effects; there was another angle to it.

    Oomphel in the Sky Henry Beam Piper
British Dictionary definitions for periastron


(astronomy) the point in the orbit of a body around a star when it is nearest to the star, esp applied to double-star systems
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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periastron in Science
  (pěr'ē-ās'trən, -trŏn)   
Plural periastra
  1. The point at which two stars orbiting each other in a binary star system are closest together.

  2. The point at which an object, such as a planet or comet, is closest to the star it is orbiting. Compare apastron.

The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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