TIME>>>>>>>---------------------------------->>>>>>>>>>------------------------------------------------------------->>>>>>>
DUST & GAS NEBULA  PROTO 
Stage 		 T Tauri  
Stage		 MAIN SEQUENCE  GIANT  
Stage 		 VARIABLE  Stage  DEATH  
Stage 		 STELLAR 
REMNANT 
 
Diffuse mass of H, He and dust ranging from a fraction of a solar mass to millions of solar masses A collision with another nebula or a shock wave from a supernova triggers a gravitational collapse into clumps ranging from a fraction of a solar mass up to 70 solar masses. Continued contraction of these objects eventually causes them to glow from the internal heat of contraction  When core T reaches ~107 K  
H-->He  
fusion begins  
Outer layers of star are  
ejected 		 H-->He fusion in core of star  
Stable stage in which star will spend most (~90%) of its life. Will continue until ~10% of the original core H has fused to He.  
At that point, H fusion reduces drastically, star contracts gravitationally.		 Gravitational contraction heats internal layers. When T reaches ~108K, He fusion begins in the core and H fusion begins in layers surrounding the core. Because of increased fusion pressure, star swells to a giant. Because of greater surface area, surface T will decrease.  Light output variations due to unstable mixing of nuclei in core  
Iron formation in core marks onset of death of star.  		 Supernova  
 

Creation of all elements from He to U.  

 Black Hole 

Pinhead sized 
Singularity 
Neutron Star 
(Pulsar) 
~10mi 
Neutrons 
Various  
mass loss processes  		 White Dwarf 
~10,000mi 
Degenerate matter 
Low Mass stars do not have a giant stage. Fusion ceases, and they shrink to white dwarfs after the main sequence stage
Objects with <0.05 MO do not generate sufficient core temperatures to initiate fusion. After the protostage, they cool to form:  ~0.05-0.025 MO:  Brown Dwarf    Entirely gaseous objects 
~0.025 MO or less:   Planet  Objects differentiated into solid and/or liquid and gaseous layers