Massive stars continue fusing elements after their helium is exhausted, building progressively heavier nuclei in a sequence of increasingly brief stages. This lesson explains how that sequence creates an onion-like interior and why iron marks the limit of ordinary energy-producing fusion.
After helium in the core is used up, the weight of the star's outer layers compresses the carbon-rich core. Compression heats the core until carbon can fuse into elements including oxygen, neon, and magnesium. When a fuel is exhausted, the core contracts and heats again, allowing another fuel to ignite.
All flashcards
Successive fusion stages
When a fuel is exhausted, core contraction raises the temperature until a heavier fuel can fuse.
Iron core
The central region of an evolved massive star where iron accumulates; fusion involving iron cannot provide net energy to support the core.
Electron capture
A process in which an electron combines with a proton, producing a neutron and a neutrino.
Neutron star
A compact remnant made mainly of neutrons, formed when neutron degeneracy pressure halts core collapse.
Surface gravity
For a spherical body, gravitational acceleration at its surface is given by g=GM/R2.
Quiz questions
During the collapse of a massive star's core, what does electron capture produce?Answer: Neutrons and neutrinos, as electrons combine with protons.
What can halt the collapse of a core that is not too massive?Answer: Neutron degeneracy pressure resisting further compression.
Why can the shock launched by a collapsing stellar core lose energy as it travels outward?Answer: It uses energy to break heavy nuclei into protons and neutrons.
How can neutrinos help drive a core-collapse supernova explosion?Answer: Some deposit energy in surrounding layers, helping push them outward.
What does the term type II supernova refer to in the described stellar evolution?Answer: A supernova caused by the collapse of a massive star's core.
Based on Astronomy 2e by Andrew Fraknoi, David Morrison, Sidney Wolff (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.