The Life of a Star

All stars begin their lives as nebula.

A star is born when gas and dust from a nebulacontract and it becomes very hot. At this point,nuclear fusion starts.

The earliest stage of a star’s life is called a protostar.

How long does a star live?

That depends on how much mass it has.

In general, smaller stars burn longer than larger stars.

In a way, they are more efficient.

A medium-sized star will last for about 10 billion years.

When a star begins to run out of fuel, its center shrinks andthe outer region expands.

At his point, it will become either a white dwarf, a neutron staror a black hole.

A white dwarf star is very dense.

It is about the size of earth, but has a mass equal to that of the Sun.

It is a white color, but has no fuel left.

A supernova is formed when a dying giant star explodes.

After, this explosion occurs, some material is left behind.

This leftover material may form a neutron star.

Neutron stars are even smaller and more dense thanwhite dwarf stars.

The largest stars become black holes when they die.

A black hole is so dense and its gravity is so strong that nothing canescape - not even light!

So how do scientists know that black holes exist?

If there is gas near a black hole, it is pulled towards itSo strongly that it rotates and spins very fast.

The gas heats up and emits x-rays, which can be detected.

A quasar is a fairly recently discovery.

It is a bright object that is very far away.

It is not a star.

Scientists think they are giant black holes in distant galaxies.

The light is created by the mass of spinning gas.