How do protoplanetary discs form?

A protoplanetary disk is a massive astronomical formation that encircles stars. It is composed of gas and dust and orbits the star similarly to Saturn's planetary rings.

Any gas and dust that remain will continue to orbit the star if it is not swallowed by it; if gravity is strong enough, enough particles remain, and collisions between particles are frequent enough, then these can come together to form planets. Until the star forms, a cloud of gas and dust floats around in space, until gravity is strong enough to pull it closer together and increasing its density, which eventually forms a star.

The gas and dust surrounding a young star form protoplanetary discs, from which material gradually accretes onto particles to form larger bodies. Planetesimals are formed through collisions and gravitational forces, and eventually planets are formed.