//astronomy/io.github.cosinekitty.astronomy/Body/SSB
The Solar System Barycenter.
This is the Solar System's center of gravity, about which the Sun and all the planets revolve. The SSB is sometimes inside the Sun, sometimes outside the Sun, depending mainly on the relative positions of the four most massive planets: Jupiter, Saturn, Uranus, and Neptune. The SSB serves as an inertial reference point that is ideal for simulating the movement of objects in the Solar System.