What is a nebula?

A nebula is a large cloud of dust and gas.

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What happens when a nebula becomes very large?

Gravity pulls the particles of dust and gas together to form a protostar. 

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What happens when a protostar becomes very large?

Gravity becomes stronger, which pulls the particles closer together and increases the temperature and pressure.


At some point nuclear fusion will start fusing hydrogen nuclei together. 

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What do we call a protostar once nuclear fusion starts?

A main sequence star.

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Which two forces are in balance in a main sequence star?

The energy released from nuclear fusion creates an outward force that balances against the inward force from gravity.

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What two things could a main sequence star become once it runs out of hydrogen?


What determines which it becomes?

If it has a relatively small mass, it will become a red giant.


If it has a relatively large mass, it will become a red super giant. 

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For a red giant, what are the final phases of the star's lifecycle?

The red giant will become a white dwarf, which will then become a black dwarf as it cools.  

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Which elements can be formed in the red giant or red supergiant phase?

Elements heavier than helium, up to iron on the periodic table. 

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For a red super giant, what happens next in the star's lifecycle?

It will explode in a supernova. 

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What two things could form after a supernova?


What determines which is formed?

If the star has a large mass, it would condense to form a neutron star.


If it has a very large mass, it would collapse to form a black hole.  

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What is a black hole?

A black hole is a region where gravity is so strong that nothing can escape.


This means no particles, or even electromagnetic radiation such as light, can escape.

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What is the Chandrasekhar limit?

The Chandrasekhar limit is the maximum mass that a stable white dwarf star can have before electron degeneracy pressure is unable to prevent gravitational collapse, about 1.4 solar masses.

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