Artistic illustration showing the aftermath of a supernova explosion as it was observed by two teams of astronomers.
Alain Labelle (View profile)Alain Labelle
The relationship between the explosive demise of massive stars called supernovas and the formation of compact objects such as black holes and neutron stars has been clearly established thanks to observations made by two teams of astrophysicists using two telescopes of the #x27;European Southern Observatory (ESO) located at La Silla Observatory, Chile.
Parallel studies from two different teams that achieve essentially the same result, it's convincing, says Professor Laurent Drissen, of Laval University, who did not participate in this work.
When massive stars die, they quickly collapse in on themselves under their own gravity, creating supernovas.
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A supernova (artistic illustration)
Astrophysicists emit the x27;hypothesis for several decades according to which the ultradense nuclei, remnants of these explosions, can transform into two types of objects depending on their mass: a neutron star or a (stellar) black hole.
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A neutron star has a well-defined dimension. It is a hard, solid surface. It’s something concrete, it’s matter. It is an extremely compact object with a radius of around ten kilometers and a mass of around once that of the Sun, explains Professor Drissen.
A black hole is not as tangible as a neutron star. It is a kind of structure in space-time that we cannot see but which can be detected by the presence of an accretion disk of matter around [the black hole ].
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Scientists still needed to prove the hypothesis that these compact objects are indeed the product of supernovas through real-time observations, that is, by collecting direct evidence of a compact remnant left by the explosion.
Our work established this direct link, says astrophysicist Ping Chen, of the Weizmann Institute of Science, in Israel, one of the lead authors of the study published in the journal Nature (New window) (in English).
This is truly the first time that a direct link has been made between a supernova explosion and the presence of a black hole or a neutron star.
A quote from Laurent Drissen, professor at Laval University
To establish this relationship, two teams, one from the Weizmann Institute and the other from Queen's University, in Northern Ireland, analyzed the data collected following the discovery of a supernova (SN 2022jli) in May 2022 in the spiral arm of the galaxy NGC 157, located 75 million light years from the Milky Way.
They were thus able to examine the consequences of this explosion.
Usually, after the explosion, the luminosity of most supernovas fades over time. This phenomenon can be confirmed by astrophysicists by a progressive decline in the light curve of the explosion.
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Artistic illustration showing the process by which a massive star within a binary system becomes a supernova.
However, this is not the case with SN 2022jli. When its overall brightness decreases, it does not do so regularly: instead it oscillates up and down approximately every 12 days, the authors explain.
In the SN 2022jli data, we see a repeating sequence of brightening and fading, notes Thomas Moore, a doctoral student at Queen's University Belfast who led the study. the supernova published in theAstrophysical Journal(New window) (in English) last October.
This is the first time that periodic oscillations repeated over many cycles have been detected in the light curve of a supernova.
A quote from Thomas Moore, doctoral student at Queen's University
The teams of Ping Chen and Thomas Moore believe that the presence of more than one star in the SN 2022jli system could explain this behavior of the light curve.
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The compact object and its companion continued to orbit each other, with the compact object steadily stealing matter to his companion when he approached it, as we can see here. (Artistic illustration)
Researchers have shown that something really remained after the supernova explosion and that this something is in orbit around a another star, as [the supernova] was before the explosion, notes Professor Drissen.
It is not uncommon for massive stars to orbit a companion star in what is called a binary system. The star behind SN 2022jli is therefore no exception to this rule.
What is remarkable is that is that the companion star appears to have survived the violent death of its partner and that the two objects, the compact remnant and the companion star, probably continued to orbit each other around the other.
The system was still gravitationally bound 300 days after the explosion.
A quote from Laurent Drissen, professor at Laval University
Both teams agree that when the companion star interacts with the material projected during the supernova explosion, its hydrogen-rich atmosphere becomes denser than before. #x27;usual.
Then, when the compact object born from the explosion passes through the atmosphere of the companion star in its orbit, it steals hydrogen gas, forming a hot disk of material around it. from him. This periodic process of flight then accretion of matter produces a lot of energy which manifests itself, in observations, in the form of regular changes in luminosity, the authors explain.
Although the teams were unable to observe any light coming from the compact object itself, they concluded that this energy theft could only be due to an invisible compact object, a star at neutrons or a black hole, which sucks matter from the inflated atmosphere of the companion star.
Know the mass of the object would allow us to establish its nature.
For example, if the mass is less than twice that of the Sun, it is most likely a neutron star. If it is higher, it is most likely a black hole.
A quote from Laurent Drissen, professor at Laval University
However, they [the authors] still cannot say whether it is a neutron star or a black hole since they were not able to carry out a spectroscopic analysis which would have made it possible to determine the mass of this object, explains Professor Laurent Drissen.
The arrival of more powerful telescopes, including the ESO European Giant Telescope (TGE) on the horizon 2027, will certainly help to better understand this very particular type of system. However, for SN 2022jli, it will be too late. This object will most likely be out of reach, but we will be able to analyze data from other supernovas, concludes Mr. Drissen.
