(ly) to vara de tarea Converter calculator in length units, light year to vara de Light year [ly] = Kilometer [km], Light year to Kilometer . A unit of length (abbreviation ly; equal to just under 10 trillion kilometres ( metres)) equal to the distance light travels in one Julian year; used to measure. She is holding a ruler which is one meter long. Every expression concerning distance and length of 1, km. 1 light year = 63, au = · m.