THE LIFE OF A STAR
What will determine how a star lives out its life? ( Examine the diagram.) How much mass a star has. What is mass? How much matter is present in a given object.
(A) First Contraction: Gravity pulls together gas and dust which eventually forms a stable star.
(1) Nebula (
Nebula: A cloud of gas and dust where stars are born!
(2) Protostar
Protostar: The first star formed where fusion begins and energy is radiated outward.
Fusion: The combining of two atomic nuclei which produces large amounts of energy/heat. Example: hydrogen + hydrogen = helium + energy
(3) Main Sequence
Main Sequence Star: A middle-aged stable star which uses hydrogen as a fuel source. Example: The Sun
(B) Second Contraction: The outflow of energy from the fusion of hydrogen is less than the gravity keeping the star together.
(C) Expansion: The star starts to fuse helium and this creates the release of energy which is greater than the force of gravity.
(4) Red Giant
Red Giant
Red Giant: A large, bright, cool star which uses helium as a fuel source.
(D,E,G) Third Contraction The supply of helium is depleted which causes the force of gravity to be greater than the energy released from the star due to fusion.
If the amount of matter in the star is average (up to 8 times the Sun’s mass),it will follow Path #1 to form a White Dwarf (5). A White Dwarf: a small,dim,hot star. A White Dwarf will eventually burn out and form a Black Dwarf (6).
White Dwarf
Nova: A star that changes in brightness and has an explosion which removes some of its outer layers.
If a star is more massive than the sun ( 8 to 20 times greater ),during the 3 rd Contraction, the outer layers will violently explode and implode, throwing matter into space as well as creating a dense core. This phenomenon is called a: Supernova (F,H).
Supernova
Supernova: A violent explosion which occurs within the outer layers of a massive collapsing star which throws matter into space as well as implodes matter into the middle forming a dense core.
The end result: A Neutron Star (7)
Neutron Star
Neutron Star: A star that forms from a collapsed star which had 8 to 20 times the mass of our Sun.
Neutron Star – Pulsar
If the star is an extremely massive star (greater than 20 Sun masses), during the 3 rd Contraction, a supernova will occur which will create a collapsed star so dense, visible light will not be able to leave its gravitational pull. This is called a --?
Black Hole (8)
Black Hole: A collapsed star so dense that visible light cannot escape its gravitational pull.