Is it true that Sun also revolves around the Earth? If yes, apart from convenience, is there another reason why we use the Solar-centered coordinate system ?
Technically, what is going on is that the Earth, Sun and all the planets are orbiting around the center of mass of the solar system. This is actually how planets orbiting other stars are often detected, by searching for the motion of the stars they orbit that is caused by the fact that the star is orbiting the center of mass of the system, causing it to wobble on the sky.
The center of mass of our solar system very close to the Sun itself, but not exactly at the Sun's center (it is actually a little bit outside the radius of the Sun). However, since almost all of the mass within the solar system is contained in the Sun, its motion is only a slight wobble in comparison to the motion of the planets. Therefore, assuming that the Sun is stationary and the planets revolve around its center is a good enough approximation for most purposes.
This page was last updated on July 18, 2015.