Astronomical units of measure
(A.U.): average distance between Earth and the Sun.
(l.-y.): distance covered in one year by the light, at the speed of 299.793 km/s.
(pc): distance from which an observer would see the major semi-axis of the terrestrial orbit under the angle of 1''.
Unit of measure
Astronomical Unit (A.U.)
(Netscape 3.0+ / MSIE 4.0+)