Far out cosmology: creating needed supernovas (Introduction)

by David Turell , Tuesday, March 31, 2020, 22:38 (1696 days ago) @ David Turell
edited by David Turell, Tuesday, March 31, 2020, 23:28

They deliver elements to us:

https://phys.org/news/2020-03-electron-eating-neon-star-collapse.html

"An international team of researchers has found that neon inside a certain massive star can consume the electrons in the core, a process called electron capture, which causes the star to collapse into a neutron star and produce a supernova.

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"An eight- to 10-solar-mass star commonly forms a core composed of oxygen, magnesium and neon (figure 1). The core is rich in degenerate electrons, meaning there is an abundance of electrons in a dense space with high enough energy to sustain the core against gravity. Once the core density is high enough, the electrons are consumed by magnesium and then neon, which are also found inside the core. Past studies have confirmed that magnesium and neon can start eating away at the electrons once the mass of the core has grown close to Chandrasekhar's limiting mass, a process called electron capture, but there has been debate about whether electron capture can cause neutron star formation. A multi-institutional team of researchers studied the evolution of an 8.4-solar-mass star and ran computer simulations on it to find an answer.

"Using newly updated data by Suzuki for density-dependent and temperature-dependent electron capture rates, they simulated the evolution of the star's core, which is supported by the pressure of degenerate electrons against the star's own gravity. As magnesium and mainly neon eat the electrons, the number of electrons decreased and the core rapidly shrunk.

"The electron capture also released heat. When the central density of the core exceeded 1010 g/cm3, oxygen in the core started to burn materials in the central region of the core, turning them into iron-group nuclei such as iron and nickel. The temperature became so hot that protons became free and escaped. Then the electrons became easier to capture by free protons and iron-group-nuclei, and the density was so high that the core collapsed without producing a thermonuclear explosion.

"With the new electron capture rates, oxygen burning was found to take place slightly off-center. Nevertheless, the collapse formed a neutron star and caused a supernova explosion, showing that an electron-capture supernova can occur.

"A certain mass range of stars with eight to 10 solar masses would form white dwarfs composed of oxygen-magnesium-neon by envelope loss due to stellar wind mass loss. If the wind mass loss is small, on the other hand, the star undergoes the electron capture supernova, as found in their simulation."

Comment: Same observation. God created a universe He knew He needed to give us the elements we need and use. dhw: wonders why the universe is like it is. ( Tuesday, March 31, 2020, 11:05)