MATTER

The periodic table is a list of all the elements in the universe. All the matter in the universe is made up of elements. Supernovas make up many of these elements. The two most common elements are hydrogen and helium. They were made when the universe was formed. Stars are made up of gases, mostly hydrogen and helium.

When hydrogen atoms form a clump, the temperature at the center of this clump goes up. Then a fusion reaction takes place and helium is formed. This reaction puts out energy in the form of radio waves, heat, X-rays, gamma rays, ultraviolet light and regular light. The clump is now a star.

When the star gets older and the hydrogen is all used up, then the helium fuses. When that happens, carbon and oxygen are formed. During this whole process, the star can get bigger and bigger, becoming a red giant star. Or if the star is much more dense which makes it hotter, oxygen and carbon will also fuse. Then heavier elements are made such as sulfur, silicon, nickel, and iron. Iron does not fuse. So elements heavier than iron do not get made by stars.

There are lots of elements heavier than iron, and many of these elements are found in stars. But since they are not made by fusion in the center of the stars, astronomers think maybe they come from supernovas, because supernovas get hotter than stars. So when a supernova explodes, these heavy elements are made, and they clump together, forming new stars and planets. All of the universe are made up of these elements. Somehow they get recycled over and over. Even people are made up of these elements.