Supernova

1
Supernova
2
Carbon Fusion

• At 15 MK carbon can fuse with four hydrogen
  nuclei to create more helium.

• At 100 MK carbon can directly fuse with helium to
  form oxygen.
• Both processes release photons.

photons and neutrinos
carbon-12
carbon-12
oxygen-16
3
Core Fusion

• High mass stars continue beyond helium and carbon
  fusion.
• Higher temperatures
• Higher pressures
• Deeper layers
• Iron is stable and doesnt fuse without massive
  added energy.

• Fusion steps
• Hydrogen to helium
• Helium to carbon
• Carbon to oxygen
• Oxygen to neon
• Neon to silicon
• Silicon to iron

4
Degenerate electrons

• The nuclei from fusion are separated from their
  electrons.
• Very close degenerate electrons
• During core fusion degenerate electrons build up.
• Electric charge opposes gravity
• Opposing forces create enormous stress

inward force of gravity
outward force of electrons
5
Death of Supergiants

• A supergiant changes temperature becoming more
  luminous.
• More than 8 M?
• Core collapses more
• Charge loses to gravity
• This becomes a type II supernova.

supernovae
Sun
6
Stellar Explosion

• When gravitational force exceeds the electron
  repulsion, the core collapses immediately.
• Energy in photons and neutrinos
• The outward energy hits collapsing material and
  the star explodes.

7
Binary Explosions

• A binary can transfer gas from a giant to a white
  dwarf.
• Increases white dwarf size
• Gravity exceeds electron repulsion
• It will explode into a type I supernova.
• Brighter than type II

white dwarf
supernova
giant star
gas pulled to partner
8
Supernova Remnants

• The supernova core collapse is at 200 billion K.
• Photon energies enough to break up iron nuclei
• Broken nuclei fuse with iron to create heavy
  elements.
• This matter goes to form new stars and planets.