Parsec

A parsec 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).

Parsec
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).
General information
Unit system	astronomical units
Unit of	length
Symbol	pc
Conversions
1 pc in ...	... is equal to ...
SI units	3.0857×1016 m
imperial & US units	1.9174×1013 mi
other astronomical	2.0626×105 AU
units	3.26156 ly

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.