Kavli Institute for the Physics and Mathematics of the Universe | University of Tokyo | 2020 Mar 30
An international team of researchers has found that neon inside a certain massive star can eat so many electrons in the core, a process called electron capture, which causes the star to collapse into a neutron star and produce a supernova.
- (a) A star core contains oxygen, neon, and magnesium. Once the core density becomes high enough, (b) magnesium and neon begin eating electrons and inducing a collapse. (c) Then oxygen burning is ignited and produces iron-group-nuclei and free-protons, which eat more and more electrons to promote further collapse of the core. (d) Finally, the collapsing core becomes a neutron star in the center, and the outer layer explodes to produce a supernova. (Credit: Zha et al.)
The researchers were interested in studying the final fate of stars within a mass range of 8 to 10 solar masses, or 8 to 10 times the mass of our Sun. This mass range is important because it includes the boundary between whether a star has a large enough mass to undergo a supernova explosion to form a neutron star, or has a smaller mass to form a white dwarf star without becoming a supernova.
An 8 to 10 solar mass star commonly forms a core composed of oxygen, magnesium, and neon. The core is rich in degenerate-electrons, meaning there is an abundance of electrons in a dense space, whose energy is high enough to sustain the core against gravity. Once the core density is high enough, the electrons get eaten by magnesium and then neon, which 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 a Chandrasekhar’s limiting mass, a process called electron capture, but there has been debate about whether electron capture can cause neutron star formation. ...
Evolution of ONeMg Core in Super-AGB Stars Toward Electron-Capture
Supernovae: Effects of Updated Electron-Capture Rate ~ Shuai Zha et al
- Astrophysical Journal 886(1):22 (2019 Nov 20) DOI: 10.3847/1538-4357/ab4b4b
- arXiv.org > astro-ph > arXiv:1907.04184 > 09 Jul 2019 (v1), 16 Oct 2019 (v4)