Astronomers have developed several ways to measure the vast distances between Earth and the stars and galaxies. What do you know about two of these techniques? A. An astronomical unit is about 93 million kilometers.

B. The A. U. is used to measure distance within our solar system.

C. A light-year (ly) is the distance that light can travel in one year in a vacuum.

D. An astronomical unit (A. U.) is the average distance between the Earth and the Sun.

E. Astronomers measure distances to objects which are outside our solar system in light-years.