Measuring The Masses Of The Earth, Sun, Moon And Planets

The mass of any celestial object, with a relatively small satellite in a circular orbit, is 4π²r³ / (GT²) where r is the orbital radius of the satellite, G is the gravitational constant, and, T is the period of the satellite:

This formula can be used to find the masses of the Earth, Sun and many planets. For the Moon, and planets with no moons, a measurement of the gravitational force on a nearby probe is used: