What is a Parsec?
A parsec is an astronomical unit of measurement that is equivalent to 3.26 light years distance, or the distance photons will travel in vacuum over the period of 3.26 years. Light travels at an approximate speed of 186,000 miles per second (300,000 kilometers per second), so a parsec represents a distance of just over 19 trillion miles (~31 trillion kilometers). By comparison, the average distance to the Sun from Earth is only 93 million miles (150,000,000 km). This distance is referred to as one astronomical unit (AU). One would have to make 103,000 round trips to the Sun to cover the distance indicated by a single parsec (206,265 AUs = 1 parsec). Our solar system, defined for example by Pluto’s orbit, is only 1/800ths of a light year across. It would have to be 2,608 times larger to equal 1 parsec across. A parsec is calculated using the parallax of 1 arc second, hence the shorter term parsec. To understand what this means it will be helpful to define the terms parallax and arc secon
