Define the unit in which astronomical distances are measured.

The size of stars and the distance between them is enormous. To express such large distances, a unit called light year is commonly used. One light year is equal to the distance traveled by light in one year. Light travels 3 × 10⁵ km in one second. A year has 365 × 24 × 60 × 60 = 3.1536 × 10⁷ seconds. Thus, light will travel a distance of 3 × 10⁵ × 3.1536 × 10⁷ km in one year. This is equal to 9.46 × 10¹² km. Thus one light year is equal to the distance of 9.46 × 10¹² km.