Astrophysicists may have unlocked the mystery of disappearing stars

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

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

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

Stars “burn” through a process called nuclear fusion, which involves combining lighter hydrogen atoms into heavier helium, releasing an enormous amount of energy in the form of light and heat. When this hydrogen begins to run out, the star enters the last stage 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, causing the outer layers to expand and cool, and the star becomes a red giant. Smaller stars – up to about 8 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 produced, at which point nuclear fusion stops, the star collapses beneath its own gravity, then explodes in a massive blast of energy. known as a supernova.

If the remaining stellar core is between 1.4 and 3 solar masses, it will collapse into a neutron star, an incredibly dense object composed primarily of neutrons, while if the core is larger than 3 solar masses, it will collapse into a black hole. , a point in space whose gravity is so strong that not even light can escape. From this.

However, this new research has found strong evidence that huge stars can die and form a black hole without any supernovas, in a process known as “complete collapse.”

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

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

“If one watched a visible star completely collapse, it could, at just the right moment, be like watching a star suddenly go out and disappear from the sky. The collapse is so complete that no explosion occurs happens, nothing escapes and no bright supernovas would be seen in the night sky Astronomers have actually observed the sudden disappearance of bright stars in recent times. We can’t be sure of a connection, but the results. that we obtained by analyzing VFTS 243 brought us much closer to a credible explanation,” Vigna-Gómez said.

This discovery was prompted by the observation of a binary star system called VFTS 243 in a small nearby galaxy known as the Large Magellanic Cloud, consisting of a large star and a black hole of one size. mass approximately 10 times greater than that of our sun.

This system is expected to have traces of the black hole star going supernova in the past, but astronomers have been unable to find any such evidence.

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

Astronomers would have expected to see signs of a “natal kick”, which is when a neutron star or black hole formed in a supernova is accelerated to between 100 and 1,000 km per second by the immense forces of the supernova explosion. The black hole in the VFTS 243 system, however, only appears to have been accelerated to around 4 km/s. Additionally, supernova forces usually affect the symmetry of a binary star system’s orbit, but no such effect has been observed in the VFTS 243 system.

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

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

“Our analysis unequivocally indicates that the VFTS 243 black hole most likely formed immediately, with energy lost primarily via neutrinos,” said co-author Irene Tamborra, also a researcher at the Niels Bohr Institute, in a press release.

It is hoped that this discovery will open new doors to the study of the death of stars and the birth of black holes.

“Our results highlight VFTS 243 as the best observable case so far for the theory of stellar black holes formed by total collapse, where the supernova explosion fails and which our models have shown is possible. “This is an important reality check for these models and we certainly hope that the system will serve as a crucial reference for future research on the evolution and collapse of stars,” Tamborra said.

Do you have a tip on a science story that News week should it cover? Do you have a question about supernovas? Let us know via science@newsweek.com.