THE NUCLEAR FUSION REACTIONS IN STARS

ARTHUR EDDINGTON

• Stars get energy from the nuclear fusion of Hydrogen nuclei. 

• Heavier elements are formed inside stars.

GEORGE GAMOW

• Derived the formula for mutual electrostatic repulsion which refers to the probability of bringing two nuclei close enough. 

HANS BETHE

• Explained how energy is produced in stars via hydrogen burning.

HYDROGEN BURNING

Is a set of stellar reactions resulting in the production of He-4 from H.

HYDROGEN BURNING

• These reactions are responsible for producing energy in stars. 

• PROTON-PROTON CHAIN REACTION 

• CARBON-NITROGEN-OXYGEN (CNO) CYCLE.

in Hydrogen Burning

Proton-Proton Chain Reaction

• Is a chain reaction by which a star transform Hydrogen into Helium. 

mutual electrostatic repulsion. 

Proton-Proton Chain Reaction

Occurs only when there is ______

1. Beta-plus decay 

2. Deuterium Burning

3. Fusion of two He-3 forming He-4 and two H

Proton-Proton Chain Reaction

Carbon-Nitrogen-Oxygen Cycle

• Is a dominant source of energy in stars about 1.3 times more massive than the sun. 

Carbon-Nitrogen-Oxygen Cycle

• Main source of Helium for such stars upon recycling Carbo-12 and finishing the whole cycle. 

C-12 fuses with a p to form N-13 and y. 

1. PROTON CAPTURE:

• Carbon-Nitrogen-Oxygen Cycle

N-13 producing C-13, positron, and neutrino. 

2. BETA-PLUS DECAY:

• Carbon-Nitrogen-Oxygen Cycle

N-14 and y. 

3. Fusion of C-13 with p to produce-

   Carbon-Nitrogen-Oxygen Cycle

N-14 fuses with p to form O-15 and y. 

4.  PROTON CAPTURE:

• Carbon-Nitrogen-Oxygen Cycle

O-15 producing N-15, positron and neutrino. 

5. BETA-PLUS DECAY:

• Carbon-Nitrogen-Oxygen Cycle
  

C-12 and He-4. 

6. Fusion of N-15 with p to produce

• Carbon-Nitrogen-Oxygen Cycle
  

HELIUM BURNING

• Refers to a set of stellar nuclear reactions that uses helium to produce energy and heavier elements such as Be, O, Ne, and Fe. 

Triple Alpha Process

• HELIUM BURNING

• Two alpha particles fuse to yield Be-8 and y. 

• Be-8 fuses with another alpha particle to form C-12 and y. 

  
  

Be-8 and y. 

• Triple Alpha Process

• Two alpha particles fuse to yield

C-12 and y. 

• Triple Alpha Process

• Be-8 fuses with another alpha particle to form

Alpha processes

• increases the size and density of the core by forming heavier elements. 

Supergiants.

Alpha Process is vital in transforming main sequence stars to s

capture of an alpha particle and the release of y. 

• Reactions that are part of the alpha process always involve the

(Fe-52)

• The Alpha process continues where the product captures and extra alpha particle until it produces the last atom in the series which is

even numbered elements. 

• All atoms produced are from