The astronomical unit of mass is the solar mass.The symbol $S$ is often used in astronomy to refer to this unit, although $M_{\odot}$ is also common. The solar mass, $1.98844 \times 10^{30} kg$, is a standard way to express mass in astronomy, used to describe the masses of other stars and galaxies. It is equal to the mass of the Sun, about 333,000 times the mass of the Earth or 1,048 times the mass of Jupiter. In practice, the masses of celestial bodies appear in the dynamics of the solar system only through the products GM, where G is the constant of gravitation.
Solar Mass