off. Stars begin their lives as parts of nebulas. Nebulas are a large

cloud of gas and dust spread out in an immense volume. The 

densest part of a nebula, gravity pulls gas and dust together. A 

contracting cloud of gas and dust with enough mass to form a 

star is called a protostar. A star is born when contracting gas and

dust from a nebula become so dense and hot that nuclear fusion

starts. Nuclear fusion is when atomic nuclei combine, releasing large amount of energy. How long a star will live depends on its mass. Stars with a 

small mass last longer than stars with a larger mass. Stars than 

have a less mass than the sun use their fuel slowly and can live

up to 200 billion years. Medium mass stars live for about 10

billion years.

of the star moves on iron can be made in the core. When the star

begins out of hydrogen they become black holes, white dwarfs,

neutron stars, planetary nebulas, and supernovas. The larger the 

size of the star means that it has a shorter life and the smaller stars

live longer. Red giants can live for many billions of years while

supergiants live about a couple hundred million years.

WHITE DWARFS: White dwarfs are the product of a red giant. They shrink to the size of the Earth, but keep the same mass from before. White dwarfs continue to glow faintly from leftover energy.

SUPERNOVAS: When supergiants run out of fuel, within hours they can explode into supernovas. This great heat from the explosion can create gold and lead. It is thought that the sun and our solarsystem is made from bits of a supernova explosion.

NEUTRON STARS: neutron stars are one of the products of a supergiant. After a supergiant dies it can turn into a neutron star . These are much smaller and denser than white dwarfs and give off flashing light signals.

BLACK HOLES: Black holes are densly packed stars that attract everything. Stars that are over 40 times as dense as the sun may become black holes. A black whole is so dense that nothing can escape its immense gravitational pull. Even light and radio waves are pulled into it.

http://www.astro.keele.ac.uk/workx/starlife/StarpageS_26M.html

The Textbook