Life Cycle of a Star

Birth

• Stars are born in the nebula, which are huge clouds of gas and dust. The nebula begins to contract under the pull of its own gravity. This forms a protostar.

Protostar

The star begins to take shape. The temperature continues to rise and nuclear fusion begins to take place. The pressure from inside the star finally equalizes the gravity pushing in, and the star stops contracting.

Nebula

Sun size stars

Huge Stars

Giant Stars

Main Sequence Star

• Stars live out the majority of their lives in a phase termed as the Main Sequence. This is the longest, most stable period of a star’s life. It converts hydrogen to helium in its core, generating heat and light.

Red Giants and Supergiants

• As the nuclear fuel becomes depleted the core contracts and our layers expand.

Sun Size Star

Sun Red Giants Planetary Nebula

White Dwarf Black Dwarf

Planetary Nebula

• Now the outer layers of the star start to drift off into space. The star loses most of its mass to the nebula.

White Dwarf

• The star cools and shrinks. No nuclear reactions take place and the faint star radiates it heat into space.

Black Dwarf

• The star will eventually lose all its heat and energy and become dark and cold.

Huge Stars

Huge Star Red Supergiant Supernova Neutron star

Supernova

• The core collapses in an instant. Forces in the core overcome the gravitational forces, causing a massive, short-lived explosion.

Neutron Star

• It contracts into a small star that has extraordinarily strong magnetic field, and a rapid spin.

Giant Stars

Giant Star Red Supergiant Supernova Black Hole

Black Hole

• It contracts and becomes a black hole. The gravitational field is so strong that even light cannot escape.

H-R Diagram

• The Hertzsprung-Russell Diagram is a graphical tool that astronomers use to classify stars according to their luminosity, spectral type, color, temperature and evolutionary stage.