Protostar

Gravitational energy was transferred to the particles, increasing their kinetic energy, so the centre became hotter. This hot, dense developing star is called a protostar.

As the material contracts, it becomes denser and hotter, producing a protostar. If its core becomes hot enough, nuclear fusion begins and it becomes a main sequence star.

As more material gathered, its gravity drew in still more, forming a dense, contracting protostar. The gas at its centre became hotter and denser as it was compressed.