![]() ![]() But as the electrons are gobbled up, the core pressure reduces. The electrons would normally keep the star’s core pressure up. This absorption of electrons is known as an electron-capture reaction. When the core gets too dense, the neon and magnesium atoms start absorbing their electrons, which are particles found bound to the nucleus or cores of atoms. Inside the core of a super-AGB star are oxygen, neon and magnesium atoms. Detailed Hubble Space Telescope images of the region, including the star before it went supernova, helped them with the identification. SN 2018zd was the only one to agree with all six. The astronomers behind this study identified six indicators necessary for a supernova to be an electron-capture supernova. Instead, for decades, astronomers have believed there must be a third type of supernova based on the electron-capture scenario. And it’s not massive enough to become a Type II supernova. So it’s too massive to end up as a Type Ia supernova. Like red supergiants, it has expanded to become large, cool and luminous.Ī super-AGB star has an intermediate mass at around 7.5 to 10 times our sun’s mass. The tongue-twisty name is a reference to where the star sits in the classic Hertzsprung-Russell diagram, which displays stars in various stages of their evolution.Ī super-AGB star is a star in a late stage of its evolution. That stands for massive super-asymptotic giant branch stars. Astronomers call this kind of star super-AGB stars. Super-AGB stars spawn electron-capture supernovaeĪnd that might be because there was also little evidence for the progenitor stars that would cause electron-capture supernova. One of the new study’s co-authors, Ken’ichi Nomoto, was one of the first to predict this possibility.īut, until now, there was no clearcut evidence anyone had seen an electron-capture supernova. Astronomers have assumed since the early 1980s that electron-capture supernovae exist. It’s said to be a “missing link” between Type Ia and Type II. The end product after this type of explosion is an exceedingly dense and small neutron star, or an even denser and smaller black hole.Īn electron-capture supernova is a third type of supernova. It then explodes in a so-called iron core collapse. Type II supernovae happen when a larger star – more than 10 times the mass of our sun – has reached the end of its life and its fuel. ![]() In the process, the white dwarf most likely disintegrates completely, leaving nothing behind. When it’s pulled enough mass to reach a critical limit, it undergoes runaway nuclear fusion and explodes as a Type Ia supernova. In this scenario, the white dwarf pulls matter from its companion. ![]() Before the white dwarf became a white dwarf, it was a star with a mass up to eight times that of our sun. Type Ia supernovae happen when a small, dense white dwarf star exists in a double system with another star. In other words, Type Ia and Type II supernovae start out as different sorts of objects, explode for different reasons, and leave behind different things. But it’s worthwhile to remember two primary types of supernovae whose physical explosion mechanisms are different from one another (The type names are, however, based on differences in their light spectra). The names and distinctions between different types of supernovae might seem bewildering. We started by asking ‘what’s this weirdo?’ Then we examined every aspect of SN 2018zd and realized that all of them can be explained in the electron-capture scenario. The team published their research in the peer-reviewed journal Nature on June 28, 2021.ĭaichi Hiramatsu, lead author of the study, said: These scientists said the Crab likely stemmed from an electron-capture supernova, too, like SN 2018zd. Astronomers believe this cloud in space may be the remnant of a supernova that exploded in the year 1054 A.D. The findings solve a mystery about one of the sky’s most famous objects, the Crab Nebula. It lies in a remote galaxy, NGC 2146, 21 million light-years away. Astronomers designate this supernova SN 2018zd. It’s a type of supernova predicted 40 years ago, but never observed until now. They announced their discovery in late June 2021. DePasquale/ Las Cumbres Observatory.įor the first time, astronomers have found convincing evidence for a new type of supernova – a new sort of stellar explosion – powered by electron capture. For 40 years, astronomers thought this kind of supernova must exist. It fits the profile for a long-sought electron-capture supernova, astronomers say. Supernova 2018zd is visible as a large, bright white dot in this image to the right of its host galaxy, NGC 2146. ![]()
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