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periastron

noun peri·as·tron \ ¦perē¦astrən , -ˌsträn \

Definition of periastron

plural periastra \-strə\
:the point in the orbit of a star or other celestial body where it is nearest to the primary star with reference to which it is revolving
  • the periastron of a comet
— compare apastron

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Origin and Etymology of periastron

New Latin, from peri- + Greek astron star

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