The word parsec is a portmanteau of "parallax of one second" and was coined by the British astronomer Herbert Hall Turner in 1913 to make calculations of astronomical distances from only raw observational data easy for astronomers.
Most stars visible to the naked eye are within a few hundred parsecs of the Sun, with the most distant at a few thousand. The nearest star, Proxima Centauri, is about 1.3 parsecs (4.2 light-years) from the Sun. The parsec unit is obtained by the use of parallax and trigonometry, and is defined as the distance at which 1 au subtends an angle of one arcsecond ( 1 / 3600 of a degree). 30.9 trillion kilometres (19.2 trillion miles). The parsec (symbol: pc) is a unit of length used to measure the large distances to astronomical objects outside the Solar System, approximately equal to 3.26 light-years or 206,265 astronomical units (au), i.e. A parsec is the distance from the Sun to an astronomical object that has a parallax angle of one arcsecond (not to scale)
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