Lesson 2: Formation of the Heavy Elements

• The origin and production of the heavy elements by fusion of lighter nuclei in the interior of stars is called Stellar nucleosynthesis.
• A supernova is the explosive death of a star.
• The first fusion process occurs in the hydrogen core of stars such as the sun with a temperature of less than 15 million K. These kinds of stars are called main-sequence stars.
• Two processes in stars, proton-proton chain and CNO cycle are believed to be the source of energy in stars.
• star balloons into a red giant. A star with a very dense helium core and a hydrogen shell expands into a red giant due to increased radiation pressure.
• Triple alpha process (TAP) occurs when the core temperature of the star is 100 million K.
• Alpha fusion process continue in the core via the alpha ladder.
• Neutron capture occurs when an atomic nucleus and one or more neutrons collide to form heavier atom.
• Elements like gold, uranium, silver, palladium, platinum and yttrium are produced by neutron capture.
• Neutron capture via the r and s processes explains the formation of elements heavier than iron. The r stands for rapid neutron capture reaction and s stands for slow neutron capture reaction.