Light-year is a unit used by astronomers to describe the distance to and between stars. It is the distance traveled in one year by a pulse of light. Light travels at 186,282 miles (299,792 kilometers) per second. One light-year therefore equals about 5.88 trillion miles (9.46 trillion kilometers). A jetliner traveling at a speed of 500 miles (800 kilometers) per hour would need to fly for 1.34 million years in order to travel one light-year. Astronomical distances are so great that even the star nearest to the earth—other than the sun—is 4.3 light-years away.
