Talking about the size of supernovae is confusing, since they are not objects, they are astronomical events: explosions of stars. There are two types depending on their explosion mechanism: gravitational collapse, more common, and thermonuclear.
Thermonuclear supernovae occur if a white dwarf captures enough mass from another star, causing its core to melt within seconds. White dwarfs are very dense objects that form when a star with a mass less than eight times the mass of the Sun has burned up all its fuel. For example, our Sun will end up becoming a white dwarf. These stellar remnants have a diameter of 1% of the diameter of the Sun and a mass similar to that of the Sun and, in many cases, they are found in binary systems, close to another star from which they can take mass. When the white dwarf captures mass from the other star, there may come a time, under certain conditions, when its core melts in seconds and causes a shock wave that destroys the star. The luminosity of the white dwarf, which was very small due to the lack of nuclear reactions inside it, increases 100 billion times. These types of supernovae are the ones that emit the most light because the star is completely destroyed.
Gravitational collapse supernovae occur when the life of a supermassive star (with masses equal to or greater than eight times the mass of the Sun) ends. At the end of their lives, these stars have an iron core surrounded by outer layers of lighter elements. At that moment, the star does not have enough energy to fuse the iron, the balance between the pressure generated by the nuclear reactions (outwards) and the gravitational pressure (inwards) is broken, the core contracts and the outer layers fall on top. the center of the star. This causes the nucleus to become very hot and the iron atoms begin to disintegrate, giving rise to a large number of neutrons. The core becomes increasingly hotter and more disintegrations occur until in less than a second all the iron disintegrates and the core collapses. What remains is a stellar core made up mainly of neutrons that emits a large number of neutrinos, very light elementary particles. These particles extract an enormous amount of energy from the star, causing it to cool. Collapse ends when the neutron density is large enough for neutron repulsion to stop the collapse. What remains is a neutron nucleus with a radius of between 10 and 20 kilometers.
Answering your question, this would be the first size to mention. This nucleus is what we call a neutron star. The size of that nucleus can be estimated using theoretical models. Another option for the fate of this type of supernova is the formation of a black hole. If the mass of the core is large enough, the neutrons are not able to stop the collapse and, instead of forming a neutron star, a black hole will be born. Due to uncertainties in our theoretical models, the exact limit of the core mass required for a black hole to form instead of a neutron star is not exactly known. In addition to giving rise to a neutron star or a black hole, gravitational collapse supernovae, like thermonuclear supernovae, expel material at enormous speeds. When the outer layers fall on the core, they rebound and a pressure wave is generated that expels them.
If your question referred more to the extent of the supernova shock wave after the explosion, here we can also make approximate calculations, although it is difficult to be precise because we do not usually have exact data on, for example, the mass of the progenitor star. or what exactly is around it. And in addition, we must take into account our lack of understanding of some processes that take place during and after the explosion.
As I mentioned, the explosion of a supernova causes the expulsion of the outer layers of the star by means of shock waves. These stellar residues end up diluting in space after millions of years. Before that, there is a period of about 400 years in which the star's material expands freely at speeds of 10,000 kilometers per second until the wave front sweeps away a large enough amount of interstellar material, equal to the mass of the star. the star layers that are in that wave front. When that happens, the expansion begins to slow down. In that time, the material has traveled about 10 light years (1 light year is 10 billion kilometers).
Afterwards, the speed of expansion decreases as more and more material is dragged without losing much energy. This ends when about 100,000 years have passed. Until this moment, the shock wave emits energy in different ranges of the electromagnetic spectrum (which can be observed by our telescopes). This phase ends when the wave front begins to radiate enough light to lose energy, which causes it to cool until between 1 million and 10 million years after the explosion. Afterwards, the remnant stops expanding and dissolves into the interstellar medium. Until then it has traveled about 300 light years.
Marina Cermeño Gavilán She has a doctorate in Theoretical Physics and a researcher at the Institute of Theoretical Physics of Madrid UAM-CSIC.
Question sent via email by Angel Lino Bayugar.
Coordination and writing: Victoria Toro.
We respond is a weekly scientific consultation, sponsored by the program L'Oréal-Unesco 'For Women in Science', which answers readers' questions about science and technology. They are scientists and technologists, partners of MY T (Association of Women Researchers and Technologists), those who answer these questions. Send your questions to [email protected] or by X #werespond.
You can follow SUBJECT in Facebook, x and instagramor sign up here to receive our weekly newsletter.
Subscribe to continue reading
Read without limits
_
#big #supernova #explodes