(Courtesy to Microsoft Encarta for these photographs.)

All stars start out in a specific place, a nebula (plural is nebulae). Nebulae are large areas of gas and dust and they are the areas where stars are born and sometimes is even where stars die. They are mainly made up of hydrogen, helium, and other gases and dust. These elements are the key ingredients in making stars. What happens later on you can find out by clicking the continue link on the bottom of the page or you can click here.

As stars go through life, they burn off simpler elements in a process known as nuclear fusion. Nuclear fusion involves making simpler, (lighter) elements into more complex (heavier) elements by combining the nuclei of different elements together under high pressure and heat. As elements get fused together, energy is released. This is proven in the equation E=mc². This equation means that a small amount of mass is equivalent to a huge amount of energy. As the star fuses its lighter elements into heavier elements, the star has a lower amount of lighter elements. When the star eventually runs out of its "light element fuel," the star tries to fuse heavier elements. As the heavier elements get fused, they become more complex and heavier too. It requires more energy to fuse the complex elements.

All stars are first born of mostly hydrogen, the simplest form of matter in space. Throughout their life, stars convert more and more hydrogen to helium, the next simplest form of matter. Helium can then be converted to oxygen or carbon if the star is large enough. Star size matters to how long it lives and how strong its gravity is. It also determines whether it can fuse together some kinds of elements or not. Small stars can only convert hydrogen to helium. Medium stars, about the size of our Sun, can fuse together helium into oxygen and carbon later on in their lives. Finally, the larger stars, more than five times the larger than the Sun, can convert oxygen and carbon to elements such as neon, sodium, magnesium, sulfur and silicon. If the star is large enough, other reactions can transform those elements into calcium and iron. To find out what happens in to the star as it dies, click here.