stellar structure and evolution

Question 1

hydrostatic equilibrium equation

Answer 1

dP/dM = -GM/r^4

Question 2

mass conservation

Answer 2

dr/dm = 1/(4pir^2rho)

Question 3

spherical symmetry

Answer 3

pressure, density, and temperature only depend on the radial component (pressure forces acting horizontally or perpendicular to the radial component cancel out, leaving only the radial component of pressure gets taken into account)

Question 4

life of the Sun (step 1)

Answer 4

core hydrogen burning on the main sequence

Question 5

life of the Sun (step 2)

Answer 5

shell hydrogen burning on the red giant branch

Question 6

life of the Sun (step 3)

Answer 6

core helium burning (with a hydrogen shell burning) in the red clump (of the cool side of the horizontal branch)

Question 7

life of the Sun (step 4)

Answer 7

helium and hydrogen shell burning on the asymptotic giant branch (AGB)

Question 8

life of the Sun (step 5)

Answer 8

a non-burning core remnant on a white dwarf cooling track, white dwarf supported by electron degeneracy pressure (which is not dependent on temperature)

Question 9

< 0.5 M_solar

Answer 9

will never be hot enough for core helium fusion
longest lived

Question 10

solar composition

Answer 10

(73% of total mass, 25% of total mass, 2% of total mass)
X = 0.73
Y= 0.25
Z = 0.2

Question 11

bound-bound absorption

Answer 11

when an electron in an atom goes from an energy to a higher energy level after absorbing a photon. this is responsible for stellar spectra. in the interiors of stars, most atoms are ionized so no electrons are bound and also those that are bound will have bound-free absorption since the photons in the stellar interiors are high energy

Question 12

bound-free absorption

Answer 12

when an electron gets kicked out the atom due to a high energy photon, this produces continuous spectra, not as important in stellar interiors since most atoms are ionized and don’t have bound electrons anyway

Question 13

free-free absorption

Answer 13

when a free electron absorbs a photon, leads to continuous spectra in the stellar atmospheres as well as stellar interiors. tend to absorb lower energy photons (because the higher up in energy, the lower the gap between the next level)