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Variable Stars and Their Pulsations

Description: Variable Stars and Their Pulsations Quiz
Number of Questions: 15
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Tags: astrophysics stellar astrophysics variable stars pulsations
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What is the primary mechanism driving the pulsations in Cepheid variable stars?

  1. Nuclear fusion reactions in the core

  2. Gravitational collapse of the core

  3. Thermal expansion and contraction of the outer layers

  4. Magnetic field interactions in the stellar atmosphere


Correct Option: C
Explanation:

Cepheid variable stars pulsate due to a delicate balance between the outward pressure from radiation and the inward pull of gravity. As the star expands, it cools and the radiation pressure decreases, causing it to contract. This contraction heats the star, increasing the radiation pressure and causing it to expand again, repeating the cycle.

What is the relationship between the pulsation period of a Cepheid variable star and its average luminosity?

  1. The pulsation period is directly proportional to the luminosity

  2. The pulsation period is inversely proportional to the luminosity

  3. There is no relationship between the pulsation period and the luminosity

  4. The relationship depends on the metallicity of the star


Correct Option: A
Explanation:

The pulsation period of a Cepheid variable star is directly proportional to the square root of its average luminosity. This relationship, known as the Leavitt Law, is crucial for using Cepheids as distance indicators in astronomy.

What is the typical range of pulsation periods for RR Lyrae variable stars?

  1. 0.2 to 1 day

  2. 1 to 10 days

  3. 10 to 100 days

  4. 100 to 1000 days


Correct Option: A
Explanation:

RR Lyrae variable stars have pulsation periods ranging from about 0.2 to 1 day. They are typically old, low-mass stars that are in the horizontal branch of the Hertzsprung-Russell diagram.

What is the primary pulsation mode for Mira variable stars?

  1. Radial pulsation

  2. Non-radial pulsation

  3. Mixed-mode pulsation

  4. Stochastic pulsation


Correct Option: B
Explanation:

Mira variable stars exhibit non-radial pulsations, where different parts of the star's surface pulsate with different amplitudes and phases. This results in the characteristic irregular light variations observed in these stars.

What is the main cause of the pulsations in Delta Scuti variable stars?

  1. Convection in the outer layers

  2. Nuclear fusion reactions in the core

  3. Gravitational waves passing through the star

  4. Magnetic field interactions in the stellar atmosphere


Correct Option: A
Explanation:

Delta Scuti variable stars pulsate due to convection in their outer layers. The convective motions generate acoustic waves that propagate through the star, causing it to pulsate.

What is the typical range of pulsation periods for white dwarf variable stars?

  1. Seconds to minutes

  2. Minutes to hours

  3. Hours to days

  4. Days to weeks


Correct Option: A
Explanation:

White dwarf variable stars, also known as pulsating white dwarfs, have pulsation periods ranging from seconds to minutes. These pulsations are driven by various mechanisms, including convection, rotation, and magnetic fields.

What is the primary pulsation mode for Beta Cephei variable stars?

  1. Radial pulsation

  2. Non-radial pulsation

  3. Mixed-mode pulsation

  4. Stochastic pulsation


Correct Option: B
Explanation:

Beta Cephei variable stars exhibit non-radial pulsations, with different parts of the star's surface pulsating with different amplitudes and phases. These pulsations are driven by instabilities in the star's radiative envelope.

What is the main mechanism responsible for the pulsations in BL Herculis variable stars?

  1. Convection in the outer layers

  2. Nuclear fusion reactions in the core

  3. Gravitational waves passing through the star

  4. Magnetic field interactions in the stellar atmosphere


Correct Option: D
Explanation:

BL Herculis variable stars pulsate due to magnetic field interactions in their stellar atmospheres. These interactions generate Alfvén waves that propagate through the star, causing it to pulsate.

What is the typical range of pulsation periods for cataclysmic variable stars?

  1. Seconds to minutes

  2. Minutes to hours

  3. Hours to days

  4. Days to weeks


Correct Option: B
Explanation:

Cataclysmic variable stars, which include novae and dwarf novae, have pulsation periods ranging from minutes to hours. These pulsations are driven by the accretion of matter from a companion star onto a white dwarf.

What is the primary pulsation mode for SX Phoenicis variable stars?

  1. Radial pulsation

  2. Non-radial pulsation

  3. Mixed-mode pulsation

  4. Stochastic pulsation


Correct Option: A
Explanation:

SX Phoenicis variable stars exhibit radial pulsations, where the entire star expands and contracts in unison. These pulsations are driven by instabilities in the star's outer layers.

What is the main mechanism responsible for the pulsations in ZZ Ceti variable stars?

  1. Convection in the outer layers

  2. Nuclear fusion reactions in the core

  3. Gravitational waves passing through the star

  4. Magnetic field interactions in the stellar atmosphere


Correct Option: A
Explanation:

ZZ Ceti variable stars pulsate due to convection in their outer layers. The convective motions generate acoustic waves that propagate through the star, causing it to pulsate.

What is the typical range of pulsation periods for AM CVn variable stars?

  1. Seconds to minutes

  2. Minutes to hours

  3. Hours to days

  4. Days to weeks


Correct Option: B
Explanation:

AM CVn variable stars, which are composed of a white dwarf and a helium-rich companion star, have pulsation periods ranging from minutes to hours. These pulsations are driven by the interaction between the two stars.

What is the primary pulsation mode for RV Tauri variable stars?

  1. Radial pulsation

  2. Non-radial pulsation

  3. Mixed-mode pulsation

  4. Stochastic pulsation


Correct Option: C
Explanation:

RV Tauri variable stars exhibit mixed-mode pulsations, where both radial and non-radial pulsation modes are present. These pulsations are driven by instabilities in the star's outer layers.

What is the main mechanism responsible for the pulsations in V1093 Herculis variable stars?

  1. Convection in the outer layers

  2. Nuclear fusion reactions in the core

  3. Gravitational waves passing through the star

  4. Magnetic field interactions in the stellar atmosphere


Correct Option: D
Explanation:

V1093 Herculis variable stars pulsate due to magnetic field interactions in their stellar atmospheres. These interactions generate Alfvén waves that propagate through the star, causing it to pulsate.

What is the typical range of pulsation periods for pulsating subdwarf B stars?

  1. Seconds to minutes

  2. Minutes to hours

  3. Hours to days

  4. Days to weeks


Correct Option: B
Explanation:

Pulsating subdwarf B stars have pulsation periods ranging from minutes to hours. These pulsations are driven by instabilities in the star's outer layers.

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