The universe contains massive quantities of stars, estimated to be around 100 billion in our own galaxy, the Milky Way. Beyond that, there are billions of other galaxies, each with their own vast collections of stars. This means the total number of stars in the universe could be as high as 1 septillion, or 1 followed by 24 zeros. Stars vary in size, brightness, and life span. They are primarily composed of hydrogen and helium and undergo nuclear fusion, which produces energy and light. The study of these celestial bodies helps astronomers understand the formation and evolution of the universe, as well as the potential for exoplanets that may support life.