Celestia Forums

What's the difference between LY and AU?

Thank you

AU - astronomical unit - the distance from the Earth to the sun. It takes roughly eight minutes for light to travel 1 AU.
LY - light year - the distance light travels in one year. For example - Alpha Centurai is about 4 light years away, and light from it takes 4 years to reach here. All nice and simple.

Also, there are roughly 63000 AU in one light year . . . The nearest star to the Sun is just over 4 light years away, or 250000 times the Earth-Sun distance.

--Chris