Supernovae

Supernovae are the spectacular demise of stars that enrich the universe. In massive stars (larger than our Sun), a core collapse occurs once fuel is exhausted. A second type involves white dwarfs in binary systems that trigger an explosion by consuming too much matter from a neighbor. The result is an explosion brighter than an entire galaxy. What remains is either an extremely dense neutron star (city-sized but with the mass of the Sun) or a black hole. The expanding nebula of debris contains heavy elements like iron or gold, which later form new solar systems and planets. A higher initial stellar mass leads to a more dramatic end and a denser remnant.