parsec [pc] Unit Converter

Definition of parsec [pc] unit

A parsec is a unit of astronomical distance equal to the distance at which one astronomical unit subtends an angle of one arcsecond. It equals approximately 3.0857 × 1016 metres, or 3.26156 light-years.

History of parsec [pc] unit

The term parsec was introduced in 1913 by British astronomer Herbert Hall Turner, who combined “parallax” and “arcsecond.” It arose from astronomers’ need for a practical distance unit based on stellar parallax: a star shifting by one arcsecond as Earth moves across an orbital baseline of one astronomical unit lies one parsec away. The concept became important as telescopic measurements improved. Although early parallaxes were difficult to determine accurately, increasingly precise observations established the parsec as a fundamental unit in professional astronomy and astrophysics.

Applications of parsec [pc] unit

Parsecs are used mainly to express distances beyond the Solar System, especially in astronomy and astrophysics. Nearby stars are commonly measured in parsecs, while kiloparsecs describe distances across the Milky Way and megaparsecs characterize separations between galaxies. Observational catalogs, research papers, and cosmological models regularly use these units because they connect naturally with parallax measurements and galactic structure.

Complete list of parsec [pc] unit conversion