University Of Central Florida (UCF) AST2002 Astronomy Final Practice Exam

Massive stars are expected to have the shortest lifespan due to the intense processes occurring within their cores. These stars, characterized by their large sizes and high temperatures, burn through their nuclear fuel at an extraordinarily rapid rate compared to smaller stars. In the core of a massive star, hydrogen is fused into helium through nuclear fusion, a process that releases a tremendous amount of energy. However, the higher mass of these stars leads to greater gravitational pressure, resulting in higher temperatures that accelerate fusion reactions. As a result, massive stars can exhaust their hydrogen fuel in just a few million years, which is considerably shorter than the lifespan of lower mass stars, which can exist for tens to even hundreds of billions of years. Additionally, after exhausting hydrogen, massive stars undergo a sequence of fusion processes, turning helium into heavier elements like carbon and oxygen, and subsequently going through stages of burning heavier and heavier elements. This lifecycle culminates in their explosive deaths as supernovae, but even the stages leading up to this point are quite short in astronomical terms. In contrast, low-mass stars and red dwarfs have much more gradual and prolonged life cycles, allowing them to exist for far longer periods. Medium-mass stars also have longer lifespans than massive stars,