Tag: evolution and end stages of stars

Questions Related to evolution and end stages of stars

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.

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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

Show answer
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

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Correct Option: A
Explanation:

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

What is a planetary nebula

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

  1. a disk of gas surrounding a protostar that may form into planets

  2. what is left of the planets around a star after a low-mass star has ended its life

  3. the expanding shell of gas that is no longer gravitationally held to the remnant of a low-mass star

  4. the molecular cloud from which protostars form

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Correct Option: C
Explanation:

A ring-shaped gaseous structure formed by an expanding shell of gas round an ageing star is known as nebula

Why does a star grow larger after it exhausts its core hydrogen?

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

  1. The outer layers of the star are no longer gravitationally attracted to the core.

  2. Hydrogen fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.

  3. Helium fusion in the core generates enough thermal pressure to push the upper layers outward.

  4. Helium fusion in a shell outside the core generates enough thermal pressure to push the upper layers outward.

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Correct Option: A,C

Compared to the star it evolved from, a white dwarf 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: B
Explanation:

A star's temperature is only 5,800 K, while a white dwarf has a temperature of 100,000 K. A white dwarf's faint luminosity comes from the emission of stored thermal energy; no fusion takes place in a white dwarf wherein mass is converted to energy. Hence it is dimmer than star

What happens to the core of a star after a planetary nebula occurs? 

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

  1. It contracts from a protostar to a main-sequence star.

  2. It breaks apart in a violent explosion.

  3. It becomes a white dwarf.

  4. It becomes a neutron star.

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Correct Option: C

During which of the following phases does the core of a massive star have so much gravity that even light can't escape?

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

  1. Neutron Star

  2. Supernova

  3. White Dwarf

  4. Black Hole

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Correct Option: D
Explanation:

Once a black hole has formed, it can continue to grow by absorbing mass from its surroundings. The gravitational force becomes so intense that even light cannot escape from it

Why do massive stars have shorter lifespans than average stars?

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

  1. They are excited to get through their lifecycles faster

  2. They have less steps in their lifecycles

  3. They burn their fuel faster

  4. They have less fuel to burn

Show answer
Correct Option: C
Explanation:

Massive stars live shorter lives than the common small stars because even though they have a larger amount of hydrogen for nuclear reactions, their rate of consuming their fuel is very much greater.