section_path: External impact/Role in stellar evolution
section_name: Role in stellar evolution
paragraph_text: Role in stellar evolution
  
  Remnants of many supernovae consist of a compact object and a rapidly expanding shock wave of material. This cloud of material sweeps up surrounding interstellar medium during a free expansion phase, which can last for up to two centuries. The wave then gradually undergoes a period of adiabatic expansion, and will slowly cool and mix with the surrounding interstellar medium over a period of about 10,000 years.
  
  The Big Bang produced hydrogen, helium and traces of lithium, while all heavier elements are synthesised in stars, supernovae, and collisions between neutron stars (thus being indirectly due to supernovae). Supernovae tend to enrich the surrounding interstellar medium with elements other than hydrogen and helium, which usually astronomers refer to as "metals". These ejected elements ultimately enrich the molecular clouds that are the sites of star formation. Thus, each stellar generation has a slightly different composition, going from an almost pure mixture of hydrogen and helium to a more metal-rich composition. Supernovae are the dominant mechanism for distributing these heavier elements, which are formed in a star during its period of nuclear fusion. The different abundances of elements in the material that forms a star have important influences on the star's life, and may influence the possibility of having planets orbiting it: more giant planets form around stars of higher metallicity.
  
  The kinetic energy of an expanding supernova remnant can trigger star formation by compressing nearby, dense molecular clouds in space. The increase in turbulent pressure can also prevent star formation if the cloud is unable to lose the excess energy.
  
  Evidence from daughter products of short-lived radioactive isotopes shows that a nearby supernova helped determine the composition of the Solar System 4.5 billion years ago, and may even have triggered the formation of this system.
  
  Fast radio bursts (FRBs) are intense, transient pulses of radio waves that typically last no more than milliseconds. Many explanations for these events have been proposed; magnetars produced by core-collapse supernovae are leading candidates.