Changing mass of sun affects accepted value of the Astronomical Unit

An "astronomical unit" or 1AU is defined as 149,597,870.691 kilometers. Officially, however, it is defined as the "the radius of an unperturbed circular orbit that a massless body would revolve about the Sun in 2π/k days (that's one year)." The problem with this, though, is that k, the mass of the sun, is not constant; so 1AU turns out not to be so constant either, making our calculations using an assumed value for 1AU more inaccurate as the sun loses mass.

click here for the full article: The "Astronomical Unit" May Need an Upgrade as the Sun Loses Mass