The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System. Parsec is approximately equal to 3.26 light-years or 206,000 astronomical units (symbol: AU), or 30.9 trillion kilometers. As an example, the nearest star, Proxima Centauri, is about 1.3 parsecs from the Sun. Most stars visible to the naked eye are within a few hundred parsecs of the Sun, with the most distant at a few thousand.
Detailed Definition:
A Parsec is the distance for which the annual parallax of the position of the Earth, viewed perpendicular to the plane of the orbit, is 1 arc second (arcsec). A parsec can equally be described as the distance from which half of the Earth's orbital major axis (equal to 1 AU) is visible as an arc of 1 arcsecond. Although distance equal to one parsec is tremendous still, multiples of parsecs are required for the larger scales in the universe, including kiloparsecs (kpc) for the more distant objects within and around the Milky Way, megaparsecs (Mpc) for mid-distance galaxies, and gigaparsecs (Gpc) for many quasars and the most distant galaxies. The term parsec is a combination of "parallax" and "arcsecond," which derives from the use of triangulation when measuring the distance between two stars.
Etymology:
Combination of words parallax and arcsecond Paralax - from Ancient Greek parállaxis, (“alteration”) Second - from Latin secundus (“following, next in order”)
Sample Sentence(s):
"Distance to the nearest star is about 1.3 parsecs." "Sci-fi franchises have been known to misuse the word parsec, mistakenly describing it as a measurement of time or speed."
