The Life Cycle of Stars

You may have noticed that all stars are not the same. Some stars are large, while some are quite small. Some stars are blue, while some are red. Like humans, stars change over time. Stars vary in composition and in temperature based on the mass that they gather during their birth and their different stages of stellar evolution. View this presentation to learn more about the evolution of stars.

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You have learned that a star will form from interstellar medium that contracts into a nebula and starts nuclear fusion. A nebula is also known as a star nursery, or a place where stars are formed. There are two main types of nebula, a reflection nebula and an emission nebula. Although they are both similar, they are also different in many ways. For instance a reflection nebula is just a large clouds of dust that simply reflects the light of nearby stars. An emission nebula that absorbs ultraviolet light then releases it as visible light in a variety of colors. To emit their own light, they must have a higher concentration of hydrogen gas. Take a look at the images below and see if you can identify the Flame Nebula and Witch Nebula. One of the nebulae is a refraction nebula, and the other is an emission nebula. Observe the witch nebula; refraction (right) and flame nebula; emission (left).

Images courtesy of NASA/JPL/ESA