STARC 2 FINAL EXAM REVIEW:
QUESTIONS AND ANSWERS LATEST
UPDATE 2026-2027
Section 1: Stellar Evolution and Death (Questions 1-25)
Question 1
Q: What is the Chandrasekhar limit for white dwarfs?
A: 1.44 M☉ (solar masses)
Rationale: The Chandrasekhar limit is the maximum mass that
can be supported by electron degeneracy pressure in a white
dwarf. Above this mass, the pressure from degenerate
electrons can no longer counteract gravity, leading to collapse.
This limit is approximately 1.44 times the mass of our Sun .
Question 2
Q: What supports a white dwarf against gravitational
collapse?
A: Electron degeneracy pressure
Rationale: Electron degeneracy pressure arises from the Pauli
exclusion principle, which states that no two electrons can
,occupy the same quantum state. When electrons are confined
to a finite volume, they exert a pressure that does not depend
on temperature and can support the star against gravity .
Question 3
Q: What is the Chandrasekhar limit for neutron stars?
A: 2-3 M☉
Rationale: The upper mass limit for neutron stars, beyond
which even neutron degeneracy pressure cannot support the
star against gravitational collapse, is approximately 2-3 solar
masses. Above this limit, the star will collapse into a black
hole .
Question 4
Q: What is the Schwarzschild radius?
A: The radius an object must have to become a black hole,
determined by setting the escape velocity equal to the speed
of light
Rationale: The Schwarzschild radius is the critical radius at
which the escape velocity from an object equals the speed of
light. Since nothing, not even light, can exceed this speed, any
,object compressed within its Schwarzschild radius becomes a
black hole .
Question 5
Q: State the escape velocity equation.
A: v² = 2GM/R
Rationale: The escape velocity is found by equating kinetic
energy (½mv²) to gravitational potential energy (GMm/R).
Solving for v gives the escape velocity equation, where G is
the gravitational constant, M is the mass, and R is the radius .
Question 6
Q: What is electron degeneracy pressure?
A: A quantum mechanical pressure exerted by electrons when
confined to a finite region
Rationale: Electron degeneracy pressure is a consequence of
the Pauli exclusion principle. When electrons are squeezed
into a small volume, they occupy higher energy states, creating
an outward pressure that is independent of temperature. This
pressure scales with radius faster than gravitational pressure,
establishing a stable equilibrium for white dwarfs .
, Question 7
Q: How does electron degeneracy pressure compare to
thermal pressure?
A: Unlike thermal pressure, electron degeneracy pressure
does not depend on temperature and can support a star
indefinitely as long as the mass remains below the
Chandrasekhar limit
Rationale: While thermal pressure depends on the
temperature of the gas, degeneracy pressure is a quantum
mechanical effect that persists even at absolute zero. This
makes it particularly important in the final stages of stellar
evolution when nuclear fusion has ceased .
Question 8
Q: What happens when a white dwarf exceeds the
Chandrasekhar limit?
A: The star will collapse
Rationale: At masses exceeding the Chandrasekhar limit, the
relativistic momentum of electrons means that gravitational
pressure and degeneracy pressure scale at the same rate.
QUESTIONS AND ANSWERS LATEST
UPDATE 2026-2027
Section 1: Stellar Evolution and Death (Questions 1-25)
Question 1
Q: What is the Chandrasekhar limit for white dwarfs?
A: 1.44 M☉ (solar masses)
Rationale: The Chandrasekhar limit is the maximum mass that
can be supported by electron degeneracy pressure in a white
dwarf. Above this mass, the pressure from degenerate
electrons can no longer counteract gravity, leading to collapse.
This limit is approximately 1.44 times the mass of our Sun .
Question 2
Q: What supports a white dwarf against gravitational
collapse?
A: Electron degeneracy pressure
Rationale: Electron degeneracy pressure arises from the Pauli
exclusion principle, which states that no two electrons can
,occupy the same quantum state. When electrons are confined
to a finite volume, they exert a pressure that does not depend
on temperature and can support the star against gravity .
Question 3
Q: What is the Chandrasekhar limit for neutron stars?
A: 2-3 M☉
Rationale: The upper mass limit for neutron stars, beyond
which even neutron degeneracy pressure cannot support the
star against gravitational collapse, is approximately 2-3 solar
masses. Above this limit, the star will collapse into a black
hole .
Question 4
Q: What is the Schwarzschild radius?
A: The radius an object must have to become a black hole,
determined by setting the escape velocity equal to the speed
of light
Rationale: The Schwarzschild radius is the critical radius at
which the escape velocity from an object equals the speed of
light. Since nothing, not even light, can exceed this speed, any
,object compressed within its Schwarzschild radius becomes a
black hole .
Question 5
Q: State the escape velocity equation.
A: v² = 2GM/R
Rationale: The escape velocity is found by equating kinetic
energy (½mv²) to gravitational potential energy (GMm/R).
Solving for v gives the escape velocity equation, where G is
the gravitational constant, M is the mass, and R is the radius .
Question 6
Q: What is electron degeneracy pressure?
A: A quantum mechanical pressure exerted by electrons when
confined to a finite region
Rationale: Electron degeneracy pressure is a consequence of
the Pauli exclusion principle. When electrons are squeezed
into a small volume, they occupy higher energy states, creating
an outward pressure that is independent of temperature. This
pressure scales with radius faster than gravitational pressure,
establishing a stable equilibrium for white dwarfs .
, Question 7
Q: How does electron degeneracy pressure compare to
thermal pressure?
A: Unlike thermal pressure, electron degeneracy pressure
does not depend on temperature and can support a star
indefinitely as long as the mass remains below the
Chandrasekhar limit
Rationale: While thermal pressure depends on the
temperature of the gas, degeneracy pressure is a quantum
mechanical effect that persists even at absolute zero. This
makes it particularly important in the final stages of stellar
evolution when nuclear fusion has ceased .
Question 8
Q: What happens when a white dwarf exceeds the
Chandrasekhar limit?
A: The star will collapse
Rationale: At masses exceeding the Chandrasekhar limit, the
relativistic momentum of electrons means that gravitational
pressure and degeneracy pressure scale at the same rate.
