What are stars made of and why do they explode?
Stars are made mainly of hydrogen, helium, carbon, and iron (more hydrogen, then helium, and finally only some carbon, and almost no iron). They operate by combining hydrogen into helium in a process called fusion. This releases heat and light. As they run out of hydrogen, they combine helium into carbon. This makes them cooler, and also causes them to swell. Eventually, they combine carbon into iron, and grow to a huge size. Eventually, they get too large and collapse back upon themsellves, and this sometimes (but not often) causes a large explosion called a supernova.
