Appearance of spiral pattern

This shows a circumstellar disc of gas with a small planet embedded in it. Initially, the disc is symmetrical around an axis perpendicular to the disc and passing through the star at its centre. The planet quickly destroys this axial symmetry – in just a few orbits. This restructured disc exerts a net gravitational influence on the planet that causes it to migrate inwards, as you can see in the next simulation. Click the forward button when you are ready to move on.