Nuclear Fussion is when two small nuclei join together forming a nucleus of a different element and RELEASING ENERGY.
Requires very HIGH TEMPERATURE (15 million degrees celcsius +)
Requires Very HIGH PRESSURE as protons in nuclei repel each other.
Elements heavier than IRON are produced in a SUPERNOVA.
Main Sequence Star Life Cycle
All stars have a life cycle.
Gravity pulls together DUST and GAS, this forms a PROTOSTAR.
The Stars MAIN SEQUENCE lasts billions of years. NUCLEAR FUSSION changes HYDROGEN TO HELLIUM, and heavier nuclei.
The star is stable due to forces being balanced within the star (inward gravitational forces match outward forces due to heat)
As Hydrogen fuel is used up, Nuclear fussion reactions change, The star expands becoming a RED GIANT
Nuclear fussion reactions change again, the inner core COLLAPSES. Star now becomes WHITE DWARF.
Nuclear Reactions form elements up to iron.
Nuclear fuels run out star cools and becomes BLACK DWARF!
DEATH OF BIGGER STARS!
A star much BIGGER than the sun becomes a RED SUPER GIANT.
When fuel used up, the CORE COLLAPSES quickly and the star explodes as a SUPERNOVA.
Elements heavier than iron form in a supernova
After the supernova, stars up to 3 times heavier than the sun become NEUTRON STARS.
HEAVIER STARS create a BLACK HOLE.