👉 In astronomy, "light years" refers to the distance a celestial object (such as a planet or a star) travels in one year. It is a unit of length used to measure astronomical distances and has its origin in the concept of time dilation caused by the Earth's rotation. Light years are typically expressed in units of light-years per second, which is equivalent to 1 light-year per year (ly). For example, if a star takes 250 ly to complete one orbit around