Transcript Supernova
Supernova
Carbon Fusion
• At 15 MK carbon can fuse
with four hydrogen nuclei to
create more helium.
carbon-12
photons and
neutrinos
• At 100 MK carbon can
directly fuse with helium to
form oxygen.
• Both processes release
photons.
carbon-12
oxygen-16
Core Fusion
• High mass stars continue
beyond helium and carbon
fusion.
– Higher temperatures
– Higher pressures
– Deeper layers
• Iron is stable and doesn’t
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
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
Death of Supergiants
-20
supernovae
Abs. Magnitude
-15
-10
-5
0
5
Sun
• A supergiant changes
temperature becoming
more luminous.
– More than 8 M
– Core collapses more
– Charge loses to gravity
10
15
20
O B A F G K M
Spectral Type
• This becomes a type II
supernova.
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.
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
giant star
gas pulled
to partner
supernova
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.