Transcript: A parsec is a distance unit appropriate to the study of stars. It’s the distance that produces a parallax shift of one arcsecond. In other words, it’s the distance where the angle subtended by the star as seen from the Earth’s orbit six months apart, spanning the orbit, is one second of arc. One parsec equals 3.26 lightyears, so a parsec is slightly larger than a lightyear. Astronomers also use multiples of the parsec, a thousand parsecs, which is a kiloparsec, and a million parsecs, which is a megaparsec. The most useful thing about the parsec unit is that it corresponds to the typical distances between stars in the Milky Way Galaxy.