3.3 The common centre of mass of our Solar System
Recall that all the objects in the Solar System orbit their mutual centre of mass, and this includes the Sun. The Sun’s orbital motion is shown in the following video, which was generated by computer calculation using freely available software. Because the Sun responds to the gravitational pull of all the other masses in the Solar System, its motion is not a simple circular orbit. Jupiter accounts for most of the Solar System mass aside from the Sun though, so the largest effect on the Sun’s movement is caused by Jupiter. If alien astronomers were watching the Sun, they would see it wobble once every 12 years in response to Jupiter’s orbit.
The viewpoint in the video is different from Section 3.1 – it’s looking from the side rather than down on the orbits. The Sun’s orbital ‘dance’ is clearer if you speed up the application by dragging the scrollbar along.