The Crab nebula
The Crab nebula is all that remains of an explosion which took place 6,000 years ago and was observed on Earth in 1054 by Chinese astronomers and Navajo Indians. It is the explosions of such supernovae that can cause atoms to capture more neutrons and form heavier elements such as platinum, gold or uranium. These are then dispersed by the explosion into the furthest reaches of the galactic space.