<P> The light - year is a unit of length used to express astronomical distances and measures 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 and measures 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>
one light year is equal to how much
one light year is equal to how much
about 9.5 trillion kilometres or 5.9 trillion miles
about 9.5 trillion kilometres or 5.9 trillion miles