Tag: evolution and end stages of stars

Questions Related to evolution and end stages of stars

Which of the following statements about degeneracy pressure is not true?

physics life cycle of stars evolution and end stages of stars the stars stars

  1. Degeneracy pressure varies with the temperature of the star.

  2. Degeneracy pressure can halt gravitational contraction of a star even when no fusion is occurring in the core.

  3. Degeneracy pressure keeps any protostar less than 0.08 solar mass from becoming a true, hydrogen-fusing star.

  4. Degeneracy pressure supports white dwarfs against gravity.

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Correct Option: A
Explanation:

Degeneracy pressure is the pressure which prevent the neutron star from becoming the Black hole.

Degeneracy pressure does not varies with the temperature of the star.

Which of the following stars will live longest? 

physics life cycle of stars evolution and end stages of stars the stars stars

  1. a 5-solar-mass star

  2. a 1-solar-mass star

  3. a 2-solar-mass star

  4. a 4-solar-mass star

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Correct Option: B
Explanation:

$a 1-$ Solar mass star:

It is a $1$ stage star that is star in its initial phase and therefore live the longest 

What is happening inside a star while it expands into a subgiant?

physics life cycle of stars evolution and end stages of stars the stars stars

  1. It is fusing hydrogen into helium in the core.

  2. It is fusing hydrogen into helium in a shell outside the core.

  3. It is fusing helium into carbon in the core.

  4. It is fusing helium into carbon in a shell outside the core.

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Correct Option: B
Explanation:

Fusion reactions take place and all hydrogen gets fuses to helium, thereby depleting hydrogen completely

Which two energy sources can help a star maintain its internal thermal pressure? 

physics life cycle of stars evolution and end stages of stars the stars stars

  1. nuclear fusion and gravitational contraction

  2. nuclear fission and gravitational contraction

  3. chemical reactions and gravitational contraction

  4. nuclear fusion and chemical reactions

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Correct Option: A
Explanation:

Fusion reaction happen on star   such as sun where hydrogen combine to form $He$ a fusion reaction releasing energy and gravitational contraction occur due to very high gravitational pull.

What happens when a star exhausts its core hydrogen supply?

physics life cycle of stars evolution and end stages of stars the stars stars

  1. Its core contracts, but its outer layers expand and the star becomes bigger and brighter.

  2. It contracts, becoming smaller and dimmer.

  3. It contracts, becoming hotter and brighter.

  4. It expands, becoming bigger but dimmer.

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Correct Option: A
Explanation:

Nuclear fusion powers a star for most of its life. Initially the energy is generated by the fusion of hydrogen atoms at the core of the main-sequence star. Later, as the preponderance of atoms at the core becomes helium, stars like the Sun begin to fuse hydrogen along a spherical shell surrounding the core. This process causes the star to gradually grow in size, passing through the subgiant stage until it reaches the red giant phase.

When they reach this phase, hydrogen in them almost becomes depleted off and they become brighter and hotter and becomes low-mass white dwarfs

At approximately what temperature can helium fusion occur? 

physics life cycle of stars evolution and end stages of stars the stars stars

  1. 100,000 K

  2. 1 million K

  3. 100 million K

  4. None of these

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Correct Option: D

Which of the following properties make flare stars so active?

physics life cycle of stars evolution and end stages of stars the stars stars

  1. fast rotation rates

  2. deep convection zones

  3. convecting cores

  4. both A and B

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Correct Option: D
Explanation:

Flare stars have deep convection zone which help in rapid transition of energy produced in the star and also has convecting cores thus both deep convection zone and convecting cores make flare stars so active.

Compared to the star it evolved from, a red giant is 

physics life cycle of stars evolution and end stages of stars the stars stars

  1. hotter and brighter.

  2. hotter and dimmer.

  3. cooler and brighter.

  4. cooler and dimmer.

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Correct Option: C
Explanation:

A red giant has lesser temperature and glows brighter and hence c is the correct option

Which of the following sequences correctly describes the stages of life for a low-mass star? 

physics life cycle of stars evolution and end stages of stars the stars stars

  1. red giant, protostar, main-sequence, white dwarf

  2. protostar, main-sequence, red giant, white dwarf

  3. protostar, red giant, main-sequence, white dwarf

  4. protostar, main-sequence, white dwarf, red giant

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Correct Option: C

Why is iron significant to understanding how a supernova occurs? 

physics life cycle of stars evolution and end stages of stars the stars stars

  1. Iron is the heaviest of all atomic nuclei, and thus no heavier elements can be made.

  2. Supernovae often leave behind neutron stars, which are made mostly of iron.

  3. The fusion of iron into uranium is the reaction that drives a supernova explosion.

  4. Iron cannot release energy either by fission or fusion.

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Correct Option: D