The Life Cycle of a Star

By Andy Kimmelshue

The birth of a star

• Stars are formed from gas and dust pulled together by gravity inside of a Nebula.

• A Nebula is a star nursery.

• Inside the Nebula, the gas and dust begin to spin and heat which creates a protostar.

Nebula

Main Sequence Stars

• As the temperature of the protostar increases, nuclear fusion begins, producing massive amounts of energy.

• At this point, these stars reach equilibrium and stay this way for the majority of their lives.

• Our sun is an example of a Main Sequence Star.

Red Giants/Supergiants

• Once the hydrogen is used up in the core, the core will contract, and the outer layers will expand, cool, and glow red.

• This increases the stars size dramatically, and depending on it’s size, it can follow two paths…………

1.) White Dwarf

• Once the helium in the core has all be converted into carbon, the core collapses, the outer layers are expelled into planetary nebula.

• The White Dwarf will eventually cool completely, and become a Black Dwarf and creating no light.

2.) Supernova• Nuclear fusion continues creating

heavier elements at the core, and causing the core to collapse in on itself.

• This force between the gravity and the atoms will cause a supernova.

Neutron Star

• If the star was 1.5 to 3 times the size of our Sun, any remaining mass will collapse into a small, dense neutron star.

• It collapses so much that protons and electrons combine to form neutrons.

• A Neutron Star has a solid surface.

Black Hole

• For stars larger than that, its remaining mass will collapse into a black hole; a deep gravitational warp in space.

• A Black Hole has an event horizonnot a solid surface.

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