Tag: life cycle of stars

Questions Related to life cycle of stars

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.

Show answer
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.

Show answer
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

What happens after a helium flash?

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

  1. The core quickly heats up and expands.

  2. The star breaks apart in a violent explosion.

  3. The core suddenly contracts.

  4. The core stops fusing helium.

Show answer
Correct Option: A
Explanation:

A helium flash is a very brief thermal runaway nuclear fusion of large quantities of helium into carbon through the triple-alpha process in the core of low mass stars (between 0.8 solar masses ( M ) and 2.0 M ) during their red giant phase . This results in heating up the core and expansion of the core takes place as a result

How many helium nuclei fuse together when making carbon?

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

  1. 2

  2. 3

  3. 4

  4. None of the above

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Correct Option: B
Explanation:

At sufficiently high temperatures and densities, a 3-body reaction called the triple alpha process can occur: Two helium nuclei ("alpha particles") fuse to form unstable beryllium.

If another helium nucleus can fuse with the beryllium nucleus before it decays, stable carbon is formed along with a gamma ray.

Which of the following stars will certainly end its life in a supernova? 

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

  1. the Sun

  2. a red giant star

  3. a 10-solar-mass star

  4. a neutron star

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Correct Option: C
Explanation:

Supernova being the last stages of a star, will happen only if the mass of the star exceeds the solar mass and hence a 10 solar mass star will have a high probability of becoming a supernova

What is a carbon star? 

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

  1. a red giant star whose atmosphere becomes carbon-rich through convection from the core

  2. a star that fuses carbon in its core

  3. another name for a white dwarf, a remnant of a star made mainly of carbon

  4. a star that is made at least 50 percent of carbon

Show answer
Correct Option: A
Explanation:

Due to triple helium process, helium fusion takes place and carbon is formed due to convection from the core