P2 - Life Cycle Of Stars Flashcards
What is the second stage in the life cycle of stars?
Gravitational energy is converted to the heat, the temperature rises until the hydrogen nuclei fuse to form helium nuclei.
The star gives out heat and light.
Describe a star’s long stable period.
The heat created by fusion provides pressure to balance gravity pulling inwards.
This is maintained for millions of years due to the hydrogen consumed.
What happens when the hydrogen supply of a star starts to run out?
Heavier elements such as iron are made by fusion of helium.
The star swells into a red giant (small) or red supergiant (large).
Why does a star become red when the hydrogen runs out?
Because the surface cools.
What happens to a small star after it becomes a red giant?
It becomes unstable and ejects its outer layer of dust and gas as a planetary nebula.
What is the last stage in the cycle of a small star?
A hot, dense core is left behind called a white dwarf.
This cools to form a black dwarf which eventually disappears.
What happens to big stars after they become red super Giants?
More fusion and expansion/contractions occur.
Heavy elements like iron are formed.
They explode in a supernova and eject iron to form new planets and stars.
What happens to an exploding supernova after explosion?
It leaves it dense core called a neutron star, which may become a black hole if the star is big enough.
What do stars initially begin to form from and how?
Clouds of dust and gas.
Gravity makes it spiral in together to form protostar.
