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parsec

[pahr-sek]
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noun Astronomy.
  1. heliocentric parallax
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Origin of parsec

First recorded in 1910–15; par(allax) + sec(ond)2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for parsec

parsec

noun
  1. a unit of astronomical distance equal to the distance from earth at which stellar parallax would be 1 second of arc; equivalent to 3.0857 × 10 16 m or 3.262 light years
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Word Origin

C20: from parallax + second ²
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

Word Origin and History for parsec

n.

interstellar distance measure, 1913, from first elements of parallax second. It is the distance at which an object has parallax (viewed from Earth) of one second of arc, or about 3.26 light-years.

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Online Etymology Dictionary, © 2010 Douglas Harper

parsec in Science

parsec

[pärsĕk′]
  1. A unit of astronomical length equal to 3.26 light-years. It is based on the distance from Earth at which a star would have a parallax of one second of arc. Its metric equivalent is about 30.8 trillion km (19.1 trillion mi). It is used in measuring distances in interstellar and intergalactic space. The closest star to Earth, Alpha Centauri, is about 1.3 parsecs away. Compare astronomical unit light-year.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.