Birth Place of Stars:

Dark and cold inter-stellar clouds

These clouds are made of more hydrogen than helium.

These clouds have very small amount of heavier elements.

Beginning;

Shock waves or any other trigger may cause contractions to begin

Gravity squeezes the particles in the nebula, pulling every particle towards the center.

As the process continues, gravitational energy is converted to thermal energy

Protostar

The Initial contraction period may last for a million year.

• The temperature of this body rises slowly until it is hot enough to radiate energy from its surface in the form of red wavelengths.

•This large red object in the center is called the protostar.

Protostar to a Star

During protostar stage, gravitational contraction continues at a rapid pace.

This causes the center to heat more intensely than the outer layers.

When the core of a protostar reaches 10 million K, pressure within is so great that nuclear fusion of hydrogen begins.

A Star is born.

Star

• Heat from the hydrogen fusion causes the increase in outward pressure.

• This pressure is balanced by gravity.

• This stage of the star is called the stable state or main sequence star stage.

• Star spends most of its life in this stage.

• As long as hydrogen is available to be fused the star will remain in that stable state.

• Beginning of the End:– Stars begin to die when they run out of

hydrogen• Gravity begins to take over

– Star begins to shrink; outer core of hydrogen begins to fuse

• Star gets bigger

• Death of Stars:– What stars end up as depend on mass

– Low and Medium mass stars• Planetary nebula --------- white dwarf

– High mass stars• Supernova --------- neutron star or black hole

• Death of Stars: Low and Medium Mass

Red Giant

Main Sequence Star

Planetary Nebula

White Dwarf

• Death of Stars: High Mass

Red Super Giant

Main Sequence Star

Supernova

Neutron Star Black Hole

• High Mass Stars:– Mass greater than 8x our sun

• Create high mass elements such as iron

– Neutron Star• Formed if remaining star < 3x sun’s mass

– Black Holes• Formed if remaining star > 3x sun’s mass

Black Holes Info Sheet

• What is a Black Hole???

– An object so massive and dense that not even light can escape its gravity

– The end result from a supernova of a star that has a mass greater than 3x the sun

• As fusion begins to slow down, the core of the sun will contract

• Temperature in the core will rise

• The outer layers of the sun will expand, consuming in the inner planets

• Sun will become a Red Giant

– Core of the sun will begin to fuse helium into larger elements such as carbon and oxygen

– Continuing over the next 100 million years…• Core will become entirely carbon and oxygen

• Core will contract

• Outer layers will expand

– Outer layers will form a planetary nebula• Core of sun will become a white dwarf

Death of a Star

• All stars run out of hydrogen and collapse due to gravity.

• More massive stars burn their fuel quickly and end their lives as supernova.

• Low mass stars do not reach the temperatures to start fusion, so they will remain red hot for billions of years.

• Low mass stars end as white dwarfs

Death of Sun An Average Star

• When fusion of lighter elements is not possible, outward pressure is reduced.

• The core starts to contract, this cause the outer layers to expand.

• This outer layer is made of gases and dust and is called the planetary nebula.

• Core of the star heats up due to contraction,

• This stage is called the white dwarf.

• White dwarf finally cools down to become black dwarf