A parsec is a unit of distance used in astronomy to measure large distances to astronomical objects outside of the Solar System. One parsec is approximately 3.26 light years, or just under 31 trillion kilometres, or 19 trillion miles. The definition states that a parsec is the distance from the Sun to an object which has a parallax angle of one arcsecond. For an example, the nearest star, Proxima Centauri, is 1.3 parsecs (4.2 light years) away from the Sun. Most of the stars visible to the naked eye in the night sky are within 500 parsecs of the Sun.
The parsec unit appears to have been suggested in 1913 by the British astronomer Herbert Hall Turner. The name "parsec" is a portmanteau of the words "parallax of one arcsecond", and it was originally designed to make calculations of astronomical distances from only their raw observational data quick and easy. While it is the unit preferred in astronomy and astrophysics, the light-year remains popular and prominent in science texts and common usage. While parsecs are used for shorter distances within the Milky Way, multiples of parsecs are required for the larger scales in the universe, including "kiloparsecs" (kpc), used for more distant objects within and around the Milky Way, "megaparsecs" (mpc), for mid-distance galaxies, and "gigaparsecs" (gpc) for several quasars and the most distant galaxies.