Week 4 Shockwaves Part 2 & Supernova Expansion

Question 1

what is important about velocities in shockwaves

Answer 1

the velocities are defined in frame of the shock front

Question 2

what is the sonic speed equation

Answer 2

cs = SQRT[γP/ρ]

where P is pressure, rho is density and gamma is the adiabatic index

Question 3

what is the Mach number equation

Answer 3

M^2 = v^2 / cs^2

Question 4

how does Mach number relate to shock

Answer 4

higher mach number means a stronger shock

Question 5

what are the two types of supernova

Answer 5

core collapse

thermonuclear

Question 6

what are the 4 phases of a supernova in order

Answer 6

phase 1 - free expansion
phase 2 - sedov expansion
phase 3 - snowplough
phase 4 - merger with ISM

Question 7

briefly describes phase 1 of a supernova

Answer 7

initial expansion is determined by velocity of ejecta.
ejecta is dense and doesn’t initially feel the presence of the ISM so acts like a vacuum
expansion starts to slow when the mass of ISM accelerated is comparable to the total ejecta mass

Question 8

briefly describe phase 2 of a supernova

Answer 8

increasing amount of mass from ISM is accelerated by shock wave and the reverse shock disappears

Question 9

briefly describe phase 3 of a supernova

Answer 9

as shock front slows down the temperature of shocked gas goes down causing it to build up at the shock front

Question 10

briefly describe phase 4 of a supernova

Answer 10

shock front slows to speed of sound and disappears

Question 11

what is constant during each phase

Answer 11

phase 1 free expansion - velocity constant
phase 2 sedov expansion - energy constant
phase 3 snowplough - density is constant
phase 4 merger with ISM - radius is constant