* Astronomy

k = 0.01720209895 A^3/2S^-1/2D^-1.

In 1939 the International Astronomical Union adopted the above value as a defining constant in astronomy. The value of the astronomical unit is derived from it, and is no longer defined by the actual orbit of the Earth. In modern ephemerides, the mean orbital axis of the Earth is slightly longer than 1 A.U., and the sidereal year is slightly shorter than 1 Gaussian year.

See more