Parsec but in globular clusters the stellar density could be from 100 to 1000 per cubic 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
Light and air unit Light and air unit A light and air unit, also known as a breathing support unit, is a specialized piece of firefighting apparatus used by firefighters to provide supplemental lighting and SCBA air bottles at the scene of an emergency. During prolonged emergencies, particularly structure fires, where firefighters must remain on air (wearing their SCBAs), these air bottles will need to be replaced and refilled. The light and air unit has the ability to refill the SCBA bottles while in the field using onboard air compressors. It also carries a supply of spare air cylinders. These units are highly customizable