Tag: evolution and end stages of stars

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

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

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

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

  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.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

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

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

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

  1. nuclear fusion and gravitational contraction

  2. nuclear fission and gravitational contraction

  3. chemical reactions and gravitational contraction

  4. nuclear fusion and chemical reactions
Reveal answer Fill a bubble to check yourself
A Correct answer
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.

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

What happens when a star exhausts its core hydrogen supply?

  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.
Reveal answer Fill a bubble to check yourself
A Correct answer
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

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

At approximately what temperature can helium fusion occur? 

  1. 100,000 K

  2. 1 million K

  3. 100 million K

  4. None of these
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Helium fusion (the triple-alpha process) requires significantly higher temperatures than hydrogen fusion to overcome the increased electrostatic repulsion of helium nuclei. This typically occurs at temperatures around 100 million Kelvin.

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

Which of the following properties make flare stars so active?

  1. fast rotation rates

  2. deep convection zones

  3. convecting cores

  4. both A and B
Reveal answer Fill a bubble to check yourself
D Correct answer
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.

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

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

  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
Reveal answer Fill a bubble to check yourself
C Correct answer
Multiple choice physics life cycle of stars evolution and end stages of stars the stars stars

Why is iron significant to understanding how a supernova occurs? 

  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.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Iron has the highest binding energy per nucleon of any element. Consequently, fusing iron consumes energy rather than releasing it, which removes the outward thermal pressure supporting a massive star's core, leading to gravitational collapse.