When the core becomes dense enough, neon and magnesium start to eat up electrons, reducing the core pressure and inducing a core-collapse supernova explosion. This is the end state of stars around 8-10 solar masses, whose core is pressure supported by electrons.

Then the electron-capture supernova should be weak, have little radioactive fallout, and have neutron-rich elements in the core.Īrtist impressions of a super-asymptotic giant branch star and its core made up of oxygen, neon and magnesium. The stars should have a lot of mass, lose much of it before exploding, and this mass near the dying star should be of an unusual chemical composition. Over the decades, theorists have formulated predictions of what to look for in an electron-capture supernova and their SAGB star progenitors. That’s the theory that was formulated beginning in 1980 by Ken’ichi Nomoto of the University of Tokyo and others. So it is a kind of reverse Goldilocks situation: The star isn’t light enough to escape its core collapsing, nor is it heavy enough to prolong its life and die later via different means. If the star had been slightly heavier, the core elements could have fused to create heavier elements, prolonging its life. This removal of electrons causes the core of the star to buckle under its own weight and collapse, resulting in an electron-capture supernova. In an electron capture supernova, some of the electrons in the oxygen-neon-magnesium core get smashed into their atomic nuclei in a process called electron capture. While gravity is always trying to crush a star, what keeps most stars from collapsing is either ongoing fusion or, in cores where fusion has stopped, the fact that you can’t pack the atoms any tighter. Composite image with data from the Hubble Space Telescope, Las Cumbres Observatory and other sources. Supernova 2018zd, marked with a white circle on the outskirts of galaxy NGC2146, is the first example of a new, third type of supernova predicted 40 years ago.

The Star and the Stellae by C.A. Nole