Question. What do you mean a disk?
Answer. The formation of disks around stars (also
known as a torus or even a doughnut) is a pretty
common occurence in astronomy. In many cases the
disks form as material falls onto the star.
If the gas is spinning then centrifigal forces give it
its disk-like shape. Gas flowing off a rapidly spinning
star can also take on a disk shape.
Below is an image of a disk of gas and dust orbiting
the star Beta Pictorus. The central region where the star is has
been block out in this picture. The disk around Beta Pictorus may
have formed planets in it.

|