Transcript Ch.9 Main sequence

Chapter 9
The Main
Sequence
Four fundamental forces of nature
Hydrostatic equilibrium: negative feedback loop
If core T drops,
•fusion rate drops,
•core contracts
•heats up
If core heats up,
•fusion rate rises
•core expands
•cools down
Main sequence stars
are modeled as
concentric spherical
shells in hydrostatic
equilibrium
Mass element dm
Constant density 
Inward force = outward force
Binding energy holds a nucleus together:
BE = total mass of each individual nucleon - mass of nucleus
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
The Coulomb barrier:
1 in 1085 particles has the energy to cross it
Wave function
Probability distribution
Quantum tunneling
Gamow Peak:
energy region where the reaction is more likely to take place
Can’t tunnel
QuickTime™ and a
through TIFF (Uncompressed)
decompressor
are needed to see this picture.
Coulomb
barrier
Few
particles
Another view of Gamow peak
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
One of 3 branches of proton-proton chain
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
CNO cycle:
C, N O atoms act
as catalysts
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
T-dependence of pp chain and CNO cycle
Solar neutrino problem:
Early searches for solar
neutrinos only found
~1/3 the expected
number of neutrinos
Solar neutrino problem:
Early searches for solar
neutrinos only found
~1/3 the expected
number of neutrinos
Neutrinos apparently can
change form. According
to nuclear physics theory,
this means they must have
mass!
“flavor oscillation”
Super-Kamiokande in Japan.
•1 km underground (in a mine)
•11,000 light-detectors in/around a pool of water
•Neutrino can (rarely) interact with a proton
•A particle is produced that moves faster than the speed of light in water
•Causes an optical “sonic boom”