parsec

American  

[pahr-sek] / ˈpɑrˌsɛk /

noun

Astronomy.

1. a unit of distance equal to that required to cause a heliocentric parallax of one second of an arc, equivalent to 206,265 times the distance from the earth to the sun, or 3.26 light-years.

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parsec British  

/ ˈpɑːˌsɛk /

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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parsec Scientific  

/ pär′sĕk′ /

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.

2. Compare astronomical unit light-year

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Etymology

Origin of parsec

First recorded in 1910–15; par(allax) + sec(ond) ²

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Example Sentences

See Examples For:

parsec

A parsec is a unit of distance used in astronomy equal to about 3.26 light years, or 30.9 trillion kilometers.

From Science Daily ● Oct. 4, 2026

No matter how many times I watch my favorite sci-fi films and series, I still can’t tell a parsec from a cylinder of drugstore plutonium.

From New York Times ● Dec. 13, 2022

Maybe there’s literally a better bounty hunter living exactly one parsec away and Herzog is a stickler for accuracy.

From Slate ● Oct. 29, 2019

The closest star, a red dwarf, is over 1 parsec away.

From Textbooks ● Oct. 13, 2016

Its length is equal to the distance of a star whose parallax is one second of arc; that is, one parsec is equal to about three and a quarter light-years.

From Astronomy: The Science of the Heavenly Bodies by David Peck Todd

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