This is because the Sun’s mass is entirely enclosed within the orbits of each of the planets, and also because the Sun is small in comparison to the distances between the Sun and planets. In the case ...This is because the Sun’s mass is entirely enclosed within the orbits of each of the planets, and also because the Sun is small in comparison to the distances between the Sun and planets. In the case of Earth, Mars, Jupiter, or any of the planets farther out in the Solar System, we could plug in the total mass of the Sun for M (note that this is the case even for Earth, which is orbiting just at the edge of our spread-out Sun).
