Astrophysics of Life - The Lives and Deaths of Stars

What eventually happens to a white dwarf it gets

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What eventually happens to a white dwarf? It gets cooler and fainter (at the same radius) What happens to higher mass stars? Gravity squeezes and heats the core enough to ignite Carbon Then Oxygen, then Neon . . . as each fuel gets exhausted in the core, its burning moves to a shell Concentric fusion shells form an “onion skin” structure Formation of an Iron core is the last stage Stars squiggle back and forth like crazy on HR diagram Why is iron formation the end of the line? Creating elements heavier than Iron requires energy With no more sources of energy, and Fe fusion taking energy from the gas, pressure support in the star’s core is lost . . . The core quickly collapses under its own weight . . . Protons and electrons are crushed together in the collapsing core, making neutrons Eventually, the neutrons are so close together they “touch” neutron degeneracy pressure (which is very stiff) The densities reach 100 billion kg/cm^3 (at those densities the whole Earth would fit in our football stadium!!) The collapsing neutron core then bounces! An explosive shock wave propagates outward, expelling all outer layers (Supernova) Crab nebula
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