Stellar Flashcards
(26 cards)
How is stellar distance typically measured?
Parallax method.
How is luminosity calculated?
L = 4πd²F, where d is distance and F is flux.
What determines a star’s temperature?
Spectral characteristics and colour indices.
How is stellar mass determined?
From binary systems, using orbital mechanics or spectroscopy.
Name three important stellar timescales.
Dynamical, thermal, and nuclear.
What does the Virial Theorem state?
2U + Ω = 0, where U is internal energy and Ω is gravitational potential energy.
What is the equation of hydrostatic equilibrium?
dP/dr = -Gm(r)ρ(r)/r²
What does the equation of state relate in a star?
Pressure P, density ρ, and temperature T.
What is mean molecular weight μ?
μ⁻¹ = ∑ (Xi/Ai), relates to composition.
What is the energy yield of the proton-proton chain?
~26.73 MeV, some carried away by neutrinos.
What fusion process creates carbon from helium?
Triple-alpha process.
What happens during silicon burning?
Nuclear statistical equilibrium is reached, leading to iron production.
Name two methods of energy transport in stars.
Radiative diffusion and convection.
What is the photon mean free path in the Sun?
~1 cm.
What is the Lane-Emden equation used for?
Modelling stellar interiors assuming a polytropic equation of state.
What is the polytropic index n for white dwarfs?
n = 3/2
What is the Chandrasekhar mass limit?
~1.4 solar masses (maximum mass for a white dwarf).
What is the dynamical stability condition for a star?
Adiabatic index γa > 4/3
What causes thermonuclear runaway in degenerate matter?
Pressure becomes independent of temperature.
What happens after hydrogen is exhausted in the core?
The core contracts, and helium burning starts if M > 0.5 M☉.
What is the final fate of stars with M > 8 M☉?
Core-collapse supernova, possible neutron star or black hole.
How does luminosity scale with mass on the main sequence?
L ∝ M³.⁵ (approximate for solar-type stars).
What triggers a Type Ia supernova?
A white dwarf accretes mass and exceeds the Chandrasekhar limit.
What is the main feature distinguishing Type II supernovae?
Collapse of an iron core in massive stars; produces a neutron star or black hole.
