Stellar Structure Part 2 Flashcards
What are the 4 stages of a 1.3 solar mass star?
A-Main sequence
B-Dissapearance of convective core
C-Hydrogen in core exhausted, He starts to build up
D- Start of red giant. H buring in shell outside growing He core
What happens after the red giant phase for a 6 solar mass star?
Increasing temp and pressure in core induces He-burning. As He core depleted get He shell burning.
What does the H-R diagram look like for a 6 solar mass star?
Main sequence going across and then loops corresponding to different shells producing energy.
What is the Virial theorem?
2K+U = 0, where K is the KE and U is the PE
How can we use the kinetic energy to determine whether a gas cloud expands or collapses?
if 2K > U then cloud expands, and if 2K < u then cloud collapses
What is the equation for the gravitational potential of a molecular cloud?
U ~ -3/5 * GMe^2/Re
What is the equation for the kinetic energy per particle of a molecular cloud?
K = 3MekT/(2μm(H))
What is Jeans mass equation?
M(J) = (5kT/Gμm(H))^3/2 * (3/4πρ0)^1/2
How can we use Jeans mass to determine whether a molecular cloud will collapse?
If M > M(J) then the cloud will gravitationally collapse.
What is the equation for Jeans radius?
R(J) = (15kT/4πGμm(H)ρ0)^1/2
What is the equation for Jeans density?
ρ(J) = 3/(4πM(J)^2) * (5kT/Gμm(H))^3
What are the ‘pillars of creation’?
Dense regions of star formation.
What happens pre-main-sequence in star formation?
- Stars evolve towards thermal equilibrium gradually, igniting the different H-burning reactions
- If star is high mass, T(centre) increases but high opacity keeps Teff ~ constant
- If star is low mass, Teff remains low enough that a radiative core never develops
What happens in post main sequence evolution?
- Red giant branch
- Core He burning
- Envelope contraction
What are the relative speeds of evolution for low and high mass stars?
Massive stars evolve much faster.
