<P> The light - year is a unit of length used to express astronomical distances . It is about 9.5 trillion kilometres or 5.9 trillion miles . As defined by the International Astronomical Union ( IAU ) , a light - year is the distance that light travels in vacuum in one Julian year ( 365.25 days ) . Because it includes the word `` year '' , the term light - year is sometimes misinterpreted as a unit of time . </P>
<P> The light - year is a unit of length used to express astronomical distances . It is about 9.5 trillion kilometres or 5.9 trillion miles . As defined by the International Astronomical Union ( IAU ) , a light - year is the distance that light travels in vacuum in one Julian year ( 365.25 days ) . Because it includes the word `` year '' , the term light - year is sometimes misinterpreted as a unit of time . </P>
how many miles in a light year wiki
how many miles in a light year wiki
5.9 trillion miles
5.9 trillion miles