Astronomical Unit to Parsec Converter

An astronomical unit (AU) is a unit of length approximately equal to the average distance from Earth to the Sun, defined as exactly 149,597,870.7 kilometers or about 93 million miles.

The astronomical unit was originally defined as the semi-major axis of Earth's orbit around the Sun. It was first estimated by Giovanni Cassini in 1672 and has been refined over centuries. In 2012, the International Astronomical Union redefined it as an exact value rather than a measured quantity.

Astronomical units are primarily used for measuring distances within the solar system, including distances between planets, asteroids, and comets. They're standard in planetary science, space mission planning, and solar system astronomy.

A parsec (pc) is a unit of length used in astronomy, equal to approximately 3.26 light-years or 206,265 astronomical units. It is defined as the distance at which one astronomical unit subtends an angle of one arcsecond.

The parsec was defined in 1913 by British astronomer Herbert Hall Turner. The name combines 'parallax' and 'arcsecond', referring to the trigonometric parallax method used to measure stellar distances. It became the preferred unit for professional astronomical distance measurements.

Parsecs are the standard unit for measuring stellar and galactic distances in professional astronomy. They're used in stellar catalogs, galactic structure studies, and cosmological research. Kiloparsecs and megaparsecs are used for larger cosmic distances.