Physics P2 7.5 The life history of a star.

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What is a protostar?
It is a gas and dust cloud in space that can go on to form a star
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How are protostars formed?
Gravitational forces pull clouds of dust and gas together to form a protostar.
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What causes the core of a protostar to get hotter and brighter?
The protostar becomes denser and the nuclei of hydrogen atoms and other light elements start to fuse together, energy is released in the process causing the core to get hotter and brighter.
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Why do stars radiate energy?
Because of hydrogen fusion in the core.
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How long does hydrogen fusion in the core of a star last?
Hydrogen fusion in the core of a star can continue for billions of years until the star runs out of hydrogen nuclei.
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How is a star stable?
Because the inward force of gravity is balanced by the outward force of radiation from the core and is called a main sequence star.
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What happens to a star when it eventually runs out of hydrogen nuclei?
It swells, cools down and turns red.
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What does the life cycle of a star eventually depend on?
It's size.
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What happens to a star similar in size to our Sun (low mass)?
It becomes a red giant.
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In the life cycle of a star, what happens to helium and other light elements?
They fuse to form heavier elements.
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What happens to a star after fusion stops?
The star will contract to form a white dwarf.
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What happens to a star after it has become a white dwarf?
Eventually no more light is emitted and the star becomes a black dwarf.
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What happens to a star much larger than the Sun?
It will swell to become a red supergiant which continues to collapse and eventually explode in a supernova.
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What happens when a red supergiant star explodes in a supernova?
The outer layers are thrown out into space and the core is left as a neutron star. If this is massive enough it becomes a black hole, the gravitational field of a black hole is so strong not even light can escape from it.
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What is the life cycle of a low mass star?
Protostar -> main sequence star -> red giant -> white dwarf -> black dwarf.
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What is the life cycle of a high mass star?
Protostar -> main sequence star -> red supergiant -> supernova -> black hole if sufficient mass.
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What will the Sun eventually become?
A black dwarf.
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What is a supernova?
The explosion of a supergiant after it collapses.
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Why are stars in the main sequence stable?
The forces acting on them are balanced.
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What is a neutron star?
The core left after a supernova explodes.
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**YOU MAY BE ASKED TO PUT THE STAGES OF THE CYCLE OF A STAR IN THE CORRECT ORDER SO MAKE SURE YOU LEARN THEM THOROUGHLY**
**LOOK UP A DIAGRAM OF THE LIFE CYCLE OF A STAR**
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Other cards in this set

Card 2

Front

How are protostars formed?

Back

Gravitational forces pull clouds of dust and gas together to form a protostar.

Card 3

Front

What causes the core of a protostar to get hotter and brighter?

Back

Preview of the front of card 3

Card 4

Front

Why do stars radiate energy?

Back

Preview of the front of card 4

Card 5

Front

How long does hydrogen fusion in the core of a star last?

Back

Preview of the front of card 5
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