Stellar Anatomy and Longevity Help (page 3)

By — McGraw-Hill Professional
Updated on Sep 17, 2011

Death Of A Star

Eventually, all the helium fuel in the core of the Sun will be spent. The core will again begin to collapse under the force of gravitation as the interior pressure drops. The rest of the Sun will follow, and the red giant will grow smaller. The internal and surface temperatures will rise, but not enough to cause further fusion reactions. The only thing stopping the inward drive of gravitation in the end will be the forces inside subatomic particles. It is believed that the Sun will come to rest at a diameter roughly the same as that of today’s Earth, and its energy output will fade away like the glow of an ember in a forgotten fire. This fate awaits all stars whose masses are less than, equal to, or somewhat greater than that of the Sun.

Stars that are much more massive than the Sun have more interesting deaths. They produce atoms heavier than carbon, including oxygen, neon, magnesium, silicon, sulfur, and iron. However, there is a limit to this. When iron is formed from fusion, it is the last hurrah. Iron will not fuse. When the iron is spent at the core, it collapses almost instantly and then rebounds, causing an outward shock wave that blows the star up. Then, in the mass that remains, gravitation can become so powerful that it overcomes everything else. The end products of some large stars are thought to be black holes , where matter has been crushed by gravitational forces so strong that time and space are altered and nothing can escape, not even the starlight. Black holes were once regarded as the figments of theorists’ imaginations, too weird to exist in the real Cosmos. Nowadays, though, there is credible evidence that they indeed exist. We’ll delve into the mysteries of these and other “stellar ghosts” in the next chapter.

Practice problems of this concept can be found at: Stars and Nebulae Practice Problems

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