P2 B the life cycle of stars

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  • Created on: 20-02-16 13:28

The life cycle of stars 1

The order of the life cycle of stars.

1. Nebulae

2. Protostar

3. Main sequence

It then splits into two routes

ROUTE 1 (STARS BIGGER THAN SUN)  /ROUTE 2 (STARS THE SAME SIZE AS THE SUN)

1. Red super giant                                      1. Red giant

2. Supernova                                              2. White dwarf

3. Neutron star or black hole (if big enough)

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The nebulae and the protostar

The nebulae

The nebulae is the first stage of the life cycle of stars.

It is a massive cloud of rock, dust and gasses.

All stars start here

The protostar

The protostar is the second stage of the life cycle of stars.

Gravity pulls the nebulae together.

The nebulae starts to heat up and the gravitatinal potential energy is converted into heat energy.

When the temperature is high enough, hydrogen nuclei undergo nuclear fusion to form helium nuclei. This is when the star is born.

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The main sequence

The main sequence

The star enters a long stable period. 

The heat goes out of the star while the gravity goes into the star. This balances the force and the star is stable.

The star maintains its energy output for millions of years due to the masive amount of hydrogen it consumes.

This stage lasts several billion years

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Route one: The red super giant route.

Once the main sequence star has finished, the star will go down one of two routes. If it is bigger than our sun, it will become a red super giant.

As the heluim and hydrogen run out, heavier elements like iron are made by the nuclear fusion of helium. The star then swells into a red super giant. It becomes red as the surface cools.

The supernova

The supernova comes after the red super giant. The star explodes in a supernova and the element are pushed into the universe to form new stars and planets.

Neutron star or black hole

The exploding supernova throws the outer layers of dust and gas into space leaving a very dense core called a neutron star. If the star is still quite big after the supernova, instead of becoming a neutron star, it will turn into a black hole.

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Route two: The red giant route

A star will go down the red giant route after the main sequence star if it is the same size as our sun. 

The red giant becomes unstable, its gravity collapses and ejects its outer layer of dust and gas as a planetary nebula.

White dwarf

After the red giant collapses, a hot dense solid core called a white dwarf is left. It cools down to become a black dwarf and then disappears. 

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Second generation stars

The dust and gas thrown from the supernova can be used to form a new star. It is like recylcing but in a space way! 

The dust and gas then loops round to form part of a nebulae and the sequence starts again. 

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