Gravity and nuclear fusion reactions drive the formation and development of stars. Stars with different masses grow and change throughout the different stages of their lives.
All the naturally occurring elementA substance made of one type of atom only. in the Universe are produced by nuclear fusion reactions in stars. For example, beryllium and carbon nuclei can be produced from helium nuclei:
During the majority of a star’s lifetime, hydrogen nuclei fuse together to form helium nuclei. As the star runs out of hydrogen, other fusion reactions take place forming the nuclei of other elements.
Elements that are heavier than hydrogen and helium are formed. Elements heavier than iron are formed in the supernovaThe large explosion at the end of a large star’s life, which distributes much of the elements formed in the star across space. explosions of high mass stars. When the supernova explodes, all the elements produced are thrown out into the Universe. The heavy elements found on Earth, such as gold, came from material thrown out in previous supernova explosions.
Professor Brian Cox demonstrates how the chemical elements are made in the death throes of a dying star