1/13/2023 0 Comments Massive star![]() ![]() As we get farther from the center, we find shells of decreasing temperature in which nuclear reactions involve nuclei of progressively lower mass-silicon and sulfur, oxygen, neon, carbon, helium, and finally, hydrogen ( Figure 23.6).įigure 23.6 Structure of an Old Massive Star. In really massive stars, some fusion stages toward the very end can take only months or even days! This is a far cry from the millions of years they spend in the main-sequence stage.Īt this stage of its evolution, a massive star resembles an onion with an iron core. Massive stars go through these stages very, very quickly. And these elements, when heated to a still-higher temperature, can combine to produce iron. ![]() The products of carbon fusion can be further converted into silicon, sulfur, calcium, and argon. After each of the possible nuclear fuels is exhausted, the core contracts again until it reaches a new temperature high enough to fuse still-heavier nuclei. ![]() This cycle of contraction, heating, and the ignition of another nuclear fuel repeats several more times. In a massive star, the weight of the outer layers is sufficient to force the carbon core to contract until it becomes hot enough to fuse carbon into oxygen, neon, and magnesium. Nuclear Fusion of Heavy ElementsĪfter the helium in its core is exhausted (see The Evolution of More Massive Stars), the evolution of a massive star takes a significantly different course from that of lower-mass stars. As we will see, these stars die with a bang. They have a different kind of death in store for them. But we know stars can have masses as large as 150 (or more) M Sun. Thanks to mass loss, then, stars with starting masses of at least 8 M Sun (and perhaps even more) probably end their lives as white dwarfs. List the hazards associated with nearby supernovae.Explain the steps of a core collapse and explosion.Describe the interior of a massive star before a supernova.By the end of this section, you will be able to: ![]()
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