Light Year
An astronomical unit of length equal to the distance light travels in a vacuum in one Julian year (365.25 days).
Governing formula
1 ly = c × 1 year ≈ 9.461 × 10¹⁵ m ≈ 63,241 AU
SI unit
Light-Years (ly)
In depth
Used in astronomy to express interstellar and intergalactic distances. One light-year equals ~9.46 trillion kilometers or ~0.3066 parsecs.
Examples in the real world
Proxima Centauri, the nearest star to the Solar System, located 4.246 light-years away.