sentence: Stars die when they run out of hydrogen or other nuclear fuel to burn and iron is produced.
sentences_before: Most black holes are made when a supergiant star dies, and leaves behind a mass that is at least one solar mass.
sentences_after: Iron does not give off energy and therefore the star has no fuel and in a short amount of time the star collapses.
concept_name: star
headings: Black hole Formation of black holes Explanation
categories: Stars Astrophysics