Nuclear Fusion & Formation of Elements

What is nuclear fusion?

The process in which light nuclei join to form heavier nuclei, releasing energy in suitable reactions.

What happens during hydrogen fusion in stars?

Hydrogen nuclei combine to form helium, releasing energy.

Why does fusion release energy in stars?

Some mass is converted into energy.

What happens to a star's mass as it releases energy through fusion?

A small amount of mass is converted into energy.

Why does fusion require extremely high temperatures?

Nuclei need enough energy to overcome electrostatic repulsion.

What is the main fusion process in the Sun?

Hydrogen fusion into helium.

Which elements can be formed by fusion in massive stars?

Elements up to iron, through successive nuclear reactions.

Why does the formation of heavier elements become possible in massive stars?

Their cores reach sufficiently high temperatures and pressures.

Why does fusion stop providing energy once iron dominates a massive star's core?

Fusion beyond iron requires an input of energy rather than releasing it.

How are elements heavier than iron formed?

Through nuclear reactions involving neutron capture and other processes, including some associated with stellar explosions.

How do supernovae contribute to the formation and distribution of heavy elements?

They can produce certain heavy elements and eject enriched material into space.

How are new stars and planets connected to earlier generations of stars?

They form from material enriched by previous stars.

Why are elements such as carbon and oxygen important evidence of stellar evolution?

They are produced by nuclear reactions inside stars.

Why can the material from a supernova contribute to a new nebula?

Ejected gas and dust can mix with interstellar material and later become part of new star-forming clouds.

Why are stars sometimes described as factories for elements?

Nuclear reactions in stars produce many of the chemical elements found in the Universe.