Stars are born in clouds of dust and
gases, mainly hydrogen. More and more gas
is pulled together by gravity to form a cloud.
After a while the cloud begins to spin. This
makes the gas atoms bump into each other at
high speeds, creating a great deal of heat. As
the cloud becomes hotter a nuclear reaction
takes place inside, and the cloud begins to
glow. This glowing cloud is called a protostar.
The protostar continues to contract until it
becomes a star.