***Much of the material in these notes on stellar evolution is discussed in this colorful video.

Star birth

Death of low-mass stars

 

Death of high-mass stars

Fusion phases for a 20-Sun star
phase duration
hydrogen 10 million years
helium 1 million years
carbon 1000 years
oxygen 1 year
silicon 1 week
iron <1 day

 

Density/size comparison of white dwarfs, neutron stars, and black holes

WATER
1 g/cm3 
SUN
1.4 g/cm3 
LEAD
11 g/cm3 
CORE OF SUN
150 g/cm3 
WHITE DWARF
106 g/cm3 
NEUTRON STAR
1015 g/cm3

 

Final composition of dead stars

Initial mass (in units of Msun)
Final evolutionary state
< 0.01
planet
0.01<M<0.08
brown dwarf
0.08<M<0.5
helium white dwarf
0.5<M<8
C-O white dwarf
8<M<10
O-Ne-Mg white dwarf
10<M<40
supernova/neutron star
40<M
supernova/black hole

Comparison of Fusion and Fission

Fusion
 
Fission
Yes
Energy source in stars?
No
bombs only
Energy source on Earth?
bombs and power plants
water
Major source on Earth
uranium
helium
Pollution?
radioactive waste

 

Flowchart of Stellar Evolution

Nova

X-ray burster (or accretion-powered pulsars)

Supernova

Type I (carbon-detonation) supernova Type II (core-collapse) supernova
results from a white dwarf in a binary system results from any supermassive star
weak hydrogen emission lines strong hydrogen emission lines
leaves no core remnant behind leaves a neutron star or black hole behind
light curve similar to that of a nova light curve usually has characteristic "plateau"
luminosity relatively constant luminosity has wide range
used as standard candle (for distance measurement) does not help with distance
several times brighter than Type II supernova about 1 billion solar luminosities

Stellar nucleosynthesis

CNO cycle

 

This page has been visited times since 12/27/06.
 Last changed: .