Astrophysicists may have solved the mystery of disappearing stars

Instead of dying dramatically in a massive supernova explosion, some massive stars can die quietly and without fanfare.

This could explain the mysterious and sudden disappearance of some stars from the night sky observed by astronomers over the years, according to a new journal article. Physical review papers.

These massive stars can completely collapse in on themselves and become black holes without a supernova, which has long been thought to be a necessary part of the death of a massive star.

Stars “burn up” through a process called nuclear fusion, which involves the combination of lighter hydrogen atoms into heavier helium, releasing a tremendous amount of energy in the form of light and heat. When this hydrogen fuel begins to run out, the star enters the later stages of its life and begins to die.

Stars can die in different ways depending on their mass. When stars run out of hydrogen, the star’s core contracts and heats up, causing the outer layers to expand and cool, and the star becomes a red giant. Smaller stars – up to 8 times the mass of our sun – will eventually expel 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 it becomes iron, at which point nuclear fusion stops, the star collapses under its own gravity, and then explodes into a huge burst of energy. known as a supernova.

If the star’s remaining core is between about 1.4 and 3 solar masses, it will collapse into a neutron star, an extremely dense object composed mostly of neutrons, while if the core is more than about 3 solar masses, it will collapses into a black hole. , a point in space with gravity so strong that even light cannot escape. from her.

However, this new research has found strong evidence that massive stars can die and form a black hole without any supernova at all, in a process known as “total collapse”.

“We believe that the core of a star can collapse under its own weight, as happens with massive stars at the end of their lives. But instead of the contraction culminating in a bright supernova explosion that will outshine the its galaxy, expected for stars more than eight times the size of the Sun, the collapse continues until the star becomes a black hole,” study co-author Alejandro Vigna-Gómez, a researcher at the Max Planck Institute for Astrophysics, of who was a postdoc at the University of Copenhagen. The Niels Bohr Institute during the study, said in a statement.

According to the researchers, this discovery could also explain the phenomenon of stars quietly disappearing from the sky without the explosive explosion of a supernova.

“If one were to stand gazing at a visible star going through a total collapse, it might be, just at the right moment, like watching a star suddenly fade and disappear from the heavens. The collapse is so complete that no “No explosion, nothing. No bright supernova would be seen in the night sky. Astronomers have actually observed the sudden disappearance of bright stars in recent times. We are much closer to a plausible explanation,” Vigna said -Gómez.

This discovery was prompted by the observation of a binary star system called VFTS 243 in a small neighboring galaxy known as the Large Magellanic Cloud, which consists of a large star and a black hole about 10 times the mass of bigger than our sun.

This system should have traces of a black hole star that went supernova in the past, but astronomers could find no such evidence.

“Normally, supernova events in star systems can be measured in various ways after they occur. But despite the fact that VFTS 243 contains a star that has collapsed into a black hole, traces of an explosion are nowhere to be found. VFTS 243 is a extraordinary system The orbit of the system has barely changed since the collapse of the star into a black hole,” said Vigna-Gómez.

Astronomers would have expected to see signs of a “natal breach”, which is when a neutron star or black hole formed in a supernova is accelerated to between 100-1000 km per second by the tremendous forces of the supernova explosion. However, the black hole in the VFTS 243 system appears to have only accelerated to about 4 km/s. Furthermore, supernova forces usually affect the orbital symmetry of a binary star system, but no such effect was seen in the VFTS 243 system.

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

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

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

This discovery is hoped to open new doors to studying how stars die and how black holes are born.

“Our results highlight VFTS 243 as the best observable case so far for the theory of stellar black holes formed through total collapse, where the supernova explosion fails, and which our models have shown to be possible. It is a check important reality for these models. And we certainly expect the system to serve as an essential reference point for future research into stellar evolution and collapse,” said Tamborra.

Do you have a tip for a science story that Newsweek should be covered? Have a question about supernovae? Tell us via science@newsweek.com.