What is a parsec defined as?

A parsec is defined as a unit of distance that is equivalent to approximately 3.26 light years. This measurement originates from the method of parallax used in astronomy to determine distances to stars and celestial objects. The term "parsec" itself is a combination of "parallax" and "arcsecond," where one parsec is determined by measuring the angle of parallax when observing a star from two different points in Earth's orbit. As a result, the parsec provides astronomers with a useful scale for expressing distances to objects beyond our solar system.

In contrast, a type of celestial body refers to specific classifications of stars, planets, and other astronomical entities, which does not relate to the specific measurement of distance. An astronomical measurement of time would focus on intervals, such as seconds or years, rather than distance. Lastly, a coordinate in the night sky pertains to a system used to pinpoint locations of celestial objects, which also does not address the concept of distance represented by a parsec.