Astrophysicists may have solved the mystery of star disappearance

Rather than dying dramatically in a massive supernova explosion, some large stars may die quietly and without much fanfare.

According to a new article in the journal, this could explain the mysterious and sudden disappearance of certain stars from the night sky that astronomers had discovered over the years Physical examination letters.

These massive stars could completely collapse and become black holes without becoming a supernova, which has long been considered a necessary part of the death of a large star.

Stars “burn” through a process called nuclear fusion, in which lighter hydrogen atoms combine to form heavier helium, releasing an enormous amount of energy in the form of light and heat. When this hydrogen fuel runs out, the star enters the later phase of its life and begins to die.

Depending on their mass, stars can die in different ways. When stars run out of hydrogen, the star’s core contracts and heats up, causing the outer layers to expand and cool, turning the star into a red giant. Smaller stars – up to about eight times the mass of our Sun – will eventually shed these outer layers and the core will become a white dwarf. Larger stars, on the other hand, go through several stages of nuclear fusion, creating heavier and heavier elements until iron is formed. At this point, nuclear fusion stops, the star collapses under its own gravity, and then explodes in a huge burst of energy known as a supernova.

When the remaining star core is between about 1.4 and 3 solar masses, it collapses into a neutron star, an incredibly dense object made mostly of neutrons. On the other hand, if the core weighs more than about 3 solar masses, it collapses into a black hole, a point in space with gravity so strong that not even light can escape.

However, this new research provides strong evidence that giant stars can die in a process called “complete collapse” and form a black hole without even going supernova.

“We think that the core of a star can collapse under its own weight, as happens with massive stars in the final stages of their lives. But instead of the contraction culminating in a bright supernova explosion that would outshine their own galaxy, as would be expected for stars more than eight times as massive as the Sun, the star continues to collapse until the star becomes a black hole,” co-author Alejandro Vigna-Gómez, a researcher at the Max Planck Institute for Astrophysics and a postdoctoral fellow at the University of Copenhagen’s Niels Bohr Institute during the study, said in a statement.

According to the researchers, this finding could also explain the phenomenon of stars silently disappearing from the sky without an explosive supernova occurring.

“If someone were to stand there and look up at a visible star undergoing a complete collapse, at the right moment it might feel like they were watching a star suddenly go out and disappear from the sky. The collapse is so complete that no explosion occurs, nothing escapes, and you wouldn’t see a bright supernova in the night sky. Astronomers have indeed observed the sudden disappearance of bright stars recently. We can’t be sure of a connection, but the results we obtained from the analysis of VFTS 243 have brought us much closer to a credible explanation,” Vigna-Gómez said.

The trigger for this discovery was the observation of a binary star system called VFTS 243 in a small neighboring galaxy, the so-called Large Magellanic Cloud, which consists of a large star and a black hole with a mass about ten times that of our Sun.

This system was supposed to show traces of a black hole star that went supernova in the past, but astronomers were unable to find any such evidence.

“Typically, supernova events in star systems can be measured in a variety of ways after they occur. But despite the fact that VFTS 243 contains a star that collapsed into a black hole, there are no traces of an explosion anywhere. It is VFTS 243.” “An extraordinary system. The system’s orbit has changed little since the star collapsed into a black hole,” said Vigna-Gómez.

Astronomers would have expected signs of a “natal kick,” in which a neutron star or black hole formed in a supernova is accelerated to 100-1000 km per second by the immense forces of the supernova explosion. However, the black hole in the VFTS 243 system appears to have only accelerated to around 4 km/s. In addition, supernova forces usually affect the symmetry of a binary star system’s orbit, but no such effects were observed in the VFTS 243 system.

“The orbit of VFTS is nearly circular and our analysis shows that there are no signs of large asymmetries during the collapse. This again suggests the absence of an explosion,” said Vigna Gomez.

Therefore, the black hole in the VFTS 243 system appears to have formed without a supernova.

“Our analysis clearly indicates that the black hole in VFTS 243 most likely formed instantly, with energy lost mainly via neutrinos,” said co-author Irene Tamborra, also a researcher at the Niels Bohr Institute, in a statement.

This discovery is expected to open up new avenues in the study of the death of stars and the formation of black holes.

“Our results underscore that VFTS 243 is the best observable case to date for the theory of stellar black holes formed by total collapse, with the supernova explosion failing, that our models have shown to be possible. It is an important reality check for these models. And we certainly expect the system to serve as a crucial benchmark for future research on stellar evolution and collapse,” Tamborra said.

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