The Life Cycle of a Star | World General Knowledge Series
Stars begin their life as diffuse clouds of gas and dust known as nebulae. The cloud begins to contract under its gravity, and part of this matter will begin to heat up and form what is called a ‘protostar’. If this protostar reaches 15 million degrees Celsius, it is hot enough to start nuclear fusion.
The first step in nuclear fusion is binding two hydrogen atoms together to form helium. The energy produced by this nuclear reaction prevents a star from contracting under its own weight, and makes it shine.