Fusion Reactions in Stars (DP IB Physics)

Fusion Reactions in Stars

• In the centre of a stable star, hydrogen atoms undergo nuclear fusion to form helium

• The equation for this reaction is:

Deuterium and tritium are both isotopes of hydrogen. They can be formed through other fusion reactions in the star

• Fusion is defined as:

  The joining of two small nuclei to produce a larger nucleus

• Low-mass nuclei (such as hydrogen and helium) can undergo fusion and release energy

• A huge amount of energy is released in the reaction

• This provides a radiation pressure that prevents the star from collapsing under its gravity

The fusion of deuterium and tritium to form helium with the release of energy

• When two protons fuse, a deuterium nucleus is produced

• In the centre of stars, the deuterium combines with a tritium nucleus to form a helium nucleus

• The total mass of the helium nucleus is less than the total mass of the individual nucleons

• Hence, the reaction releases energy, which provides fuel for the star to continue burning

Fusion & The Strong Nuclear Force

• For two nuclei to fuse, both nuclei must have high kinetic energy

• This is because

  • Nuclei must overcome the repulsive coulomb forces between protons

  • The strong nuclear force, which binds nucleons together, has a very short range

• Therefore, nuclei must get very close together for the strong nuclear force to take effect

• This means an extremely hot and dense environment is required to achieve fusion