Despite having the word "year" in its name, a light year is not a unit of time. Instead, it is a unit of distance used in astronomy to measure the vast distances between celestial objects like stars, galaxies, and nebulae. CONCEPT: Light year: The distance traveled by light in one year is called a light-year. It is the unit of astronomical distance. 1 light-y The distance that light travels in a vacuum in one Julian year (365,25 days) is a light-year. The light-year unit appeared in 1838 by Friedrich Bessel after the first accurate calculation of the distance to a star other than the Sun. A light year is the distance light travels in a vacuum in one Earth year. Learn how to measure distances in light years and compare it with other units of length in astronomy.
