Parsec Parsec The parsec (symbol: pc) is a unit of length used to measure large distances to astronomical objects outside the Solar System. A parsec is defined as the distance at which one astronomical unit subtends an angle of one arcsecond, which corresponds to astronomical units. One parsec is equal to about 3.26 light-years (30 trillion km or 19 trillion miles) in length. The nearest star, Proxima Centauri, is about from the Sun. Most of the stars visible to the unaided eye in the night sky are within 500 parsecs of the Sun. The parsec unit was probably first suggested in
Light and air unit and can vary greatly between departments. These multifunctional units are also equipped with diesel generators which supplies electricity to power portable lights and overall scene illumination. This is usually done via a roof mounted telescoping light bank. The unit also has the ability to supply electrical power in an emergency to a shelter, base camp, or medical facility. In the United States, Chapter 24 of National Fire Protection Association regulation 1901 outlines specifications for any air system mounted on firefighting apparatus. Light and air unit A light and air unit, also known as a breathing support unit, is a specialized