When a high-mass star has no hydrogen left to burn, it expands and becomes a red supergiant. While most stars quietly fade away, the supergiants destroy themselves in a huge explosion, called a supernova. The death of massive stars can trigger the birth of other stars.
The original rock ( protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (100 megapascals (1,000 bar) or more), causing profound physical or chemical change.
