单词	parsec
释义	parsec /ˈpɑːsɛk / noun A unit of distance used in astronomy, equal to about 3.26 light years (3.086 × 1013 kilometres). One parsec corresponds to the distance at which the mean radius of the earth’s orbit subtends an angle of one second of arc.But cosmologists are so comfortable with millions and billions that none of them feel the urge to invent a unit much beyond the light-year or the parsec.... I mean, all the ones that I've looked at so far are within 100 parsecs of 300 light years of the Sun. For reference, one parsec is around three light years. Origin Early 20th century: blend of parallax and second2.
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