Scientists have discovered a completely new type of stellar explosion (an explosion at the end of a star's life), which they have called an "electron-capture" supernova. Essentially, this new type of supernova adds to the two types that scientists have already discovered, but more importantly, the discovery helps solve a mystery that has been going on for about a thousand years.
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In the year 1054 AD, people around the world reported seeing the sky illuminated by a bright light. It was so bright that it could be seen even during the day for 23 days and was visible in the night sky for almost two years.
This phenomenon results in the so-called Crab Nebula, which has been studied in detail by astronomers to this day. But the new study confirms where this explosion came from.
Scientists had previously hypothesized that such supernovae could exist for 40 years and had suggested that they likely originated from massive super-AGB stars (super-asymptotic giant branch stars). However, research on these stars and supernovae was lacking and there was not much evidence.
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Now scientists have found one such example of a supernova, in the galaxy NGC 2146. This stellar explosion was close enough that scientists were able to find the star in archival images taken before it exploded, allowing them to glean detailed information about how it did it.
The example known as SN 2018zd has some strange features, many of which have never been observed in a supernova before, leading scientists to conclude that it is a new type of stellar explosion (supernova).
A paper describing the findings, “The electron-capture origin of supernova 2018zd,” has been published in Nature Astronomy.
Scientists have divided supernovae into two main types. In the first type, a white dwarf star explodes after absorbing material (mass) from a companion star and at some point reaches a critical mass absorption limit, the so-called Chandrasekhar limit. The core becomes denser. It will then undergo a thermonuclear explosion, collapsing under the force of gravity. The second type occurs when a massive star stops producing energy in its core, so it collapses under the force of its own gravity.
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The new type of supernova combines something of both.
Scientists suggested this might have happened more than 40 years ago, when researchers including Ken'ichi Nomoto of the University of Tokyo suggested that such a supernova explosion could occur. Since then, researchers have been drawing up a theory of what such an explosion would look like.
Source: The Independent
