Nebula
Nebulas provide raw materials from which stars form.Under certain conditions, portions of a nebula begin to contract, forming clumps of spinning gases. Over millions of years, gravity causes these clumps to condenseinto dense pockets of matter within the nebula. These pockets of matter form the beginnings of stars and are called protostars.
Protostars
As a protostar continues to condense, its particles are squeezed closer and closer together, creating enormous pressure at the center. This pressure causes the core of the protostar to become extremely hot. When the core's temperature becomes 15,000,000°C the nuclear reaction begins, releasing tremendous amounts of energy. At this point, the protostar stops condensing and begin to glow. Now it is a star.
