Supernovae are classified by their spectra.
If a spectrum contains hydrogen, it is classified as Type II, otherwise as Type I.
This also betrays the physical mechanism that caused the star to blow apart.
Astronomers now believe that both supernova 2018zd and the supernova
that created the Crab Nebula 1000 years ago were both of elusive Type III.
Quote:
|
Originally Posted by Charles Q. Choi , space.com
For decades, scientists have known of two main supernova types. Large stars more than 10 times the mass of the sun collapse in their centers when their cores burn all their fuel, causing the outer layers to explode and leaving behind a neutron star or black hole. In contrast, stars less than eight times the sun's mass burn out over time to leave a dense core of ash known as a white dwarf, and these remnants can pull fuel onto themselves off companion stars until they detonate in a thermonuclear explosion.
Stars between eight and 10 solar masses should theoretically explode in a different way. Their gigantic internal pressures would force electrons to fuse with atomic nuclei. These electrons normally repel each other, so their removal leads to a drop in pressure inside the star. The star's core then collapses, setting off an explosion of the surrounding layers and leaving behind a neutron star slightly more massive than the sun.
Astrophysicist Ken'ichi Nomoto at the University of Tokyo and his colleagues first theorized such "electron-capture" supernovas in 1980. Over the decades, scientists developed predictions of what to look for in an electron-capture supernova and its progenitor star, but they had never actually confirmed a star detonating in this manner.
|
Article here :-
https://www.space.com/new-supernova-type-discovery
Paper
"The electron-capture origin of supernova 2018zd" by Hiramatsu et. al. :-
https://arxiv.org/pdf/2011.02176.pdf
