Parsec

Parsec
Stellarparallax parsec1.svg
A parsec is the distance from the Sun to an astronomical object which has a parallax angle of one arcsecond. (the diagram is not to scale).
Standard:	astronomical units
Quantity:	length
Symbol:	pc
Expressed in:	1 pc =
SI units	3.0857×1016 m
imperial & US units	1.9174×1013 mi
other astronomical	2.0626×105 AU
units	3.26156 ly

The parsec (symbol: pc) is a unit of distance used in astronomy. It is the distance that light travels in 3.26 years, or just under 31 trillion kilometres (about 19 trillion miles).

This is from the definition: a parsec is the distance from the Sun to an object which has a parallax angle of one arcsecond. The technique used in the calculation is trigonometry.

It takes 3.26 years for the light to come from a parsec away.

Parsec Media

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  Stellar parallax motion from annual parallax

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  Diagram of parsec.

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  As observed by the Hubble Space Telescope, the astrophysical jet erupting from the active galactic nucleus of M87 subtends 20″ and is thought to be 1.5 kiloparsecs (4,892 ly) long (the jet is somewhat foreshortened from Earth's perspective).

Related pages

• Astrometry

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