by Scientists found strong evidence that some huge stars end with a whimper, not a bang, and sink into a black hole of their own making without light and anger supernova.
To understand why this is important, we need to start with a crash course in stellar evolution. Stars generate energy through nuclear fusion processes in their hearts by which they turn hydrogen into helium. When stars are at least eight times the the mass of our sun they run out of that hydrogen supply, start fusion reactions using other elements — helium, carbon, oxygen, and so on, until they end up with an inert iron core that requires more energy to be put into the reaction fusion than it can. production. At this stage, the fusion reactions cease, and the energy production that keeps the star up evaporates. Suddenly, gravity breaks free and causes the core to collapse, while the outer layers of the star escape the contracting core and explode – sparking a supernova that could be brighter for several weeks. sometimes. galaxy.
Meanwhile, the falling heart forms a dense object. This object is often spinning neutron star called a pulsar — but, under certain conditions, it could become a stellar-mass black hole. This is the standard story of realistic timelines. However, astronomers are starting to come around to the idea that some stars that produce black holes may do so that supernova explosion.
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Researchers have noted occasional occurrences of it failed supernovas — stars that begin to glow as if they are about to explode, but then rise and die. Elsewhere, studies of old photographic plates form part of it Objectives Discovered in Escape for One Hundred Years of Observation (VASCO) project, led by Beatriz Villarroel, many stars have been found on the old plates that are no longer visible; it is like they have disappeared without a trace.
Could these failed supernovae and fading stars be evidence that almost all stars have been pulled into the black hole they create before they have a chance to explode? Well, maybe, believe some scientists.
“If one were to stand looking up at a visible star going through total collapse, it could, at just the right time, be like watching a star suddenly turn off and disappear from the heavens,” said Alejandro Vigna-Gómez from the Max Planck Institute for Astrophysics in Germany statement. “Astronomers have really noticed the sudden disappearance of bright stars in recent years.”
Although the idea is still only a theory, there is now strong supporting evidence in the form of a strange binary system studied by Vigna-Gómez and his team. Designated VFTS 243, the system was found in 2022 and lives in the Tarantula Nebula, located in the Large Magellanic Cloud; there is a 25-solar-mass star and a 10-solar-mass black hole that, in cosmic terms, must have been produced by a massive star that recently reached the end of its life.
“VFTS 243 is an extraordinary system,” said Vigna-Gómez. “Despite the fact that VFTS 243 contains a star that has fallen into a black hole, the trace of the explosion is nowhere to be found.”
For example, the orbits of the star and black hole in VFTS 243, around their common center of mass, are still nearly circular. However, supernova explosions are asymmetric, with slightly more energy being produced in one direction than the other, which should be attributed to the compact object forming a “birth kick.” Such a kick would accelerate the dense object, causing its orbit to expand and become more distant. Typically, this kick is between 30 and 100 kilometers (19 and 62 miles) per second, but the black hole in VFTS 243 is only four kilometers (2.5 miles) per second at most.
The effects of natal kicks have been observed in pulsars before, but never in stellar mass black holes. This may be telling us something about how stellar-mass black holes are formed, and VFTS 243 is the clearest view yet of the results of this process.
Natal kicks are the result of three things: ejecting debris from the exploding star, bursting neutrino from the core of the falling star, and gravitational waves. If there were no supernova, however, there would be no debris, leaving only the neutrinos and gravitational waves to provide a much smaller kick — which is exactly what we see in VFTS 243 .
If this is correct, it means that many of the biggest stars in the universe, which shine so brightly, end their lives in silent darkness as they are pulled into a black hole. This could be the final fate of the star that lives in VFTS 243 when it reaches the end of its life.
There are also wider consequences. A supernova explosion is a factory of elements. Elements such as oxygen, carbon and nitrogen in the outer layers of a dying star are not only blasted in space where they can be recycled into the next generation of stars and planets, the intense heat and energy of the supernova shock can create even heavier elements in the supernova debris. For example, one of the reasons a supernova shines so brightly for so long is that cobalt and iron are created as a result of the radioactive decay of nickel isotopes produced in the explosion.
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However, if some massive stars are completely collapsing into black holes without supernova explosions, they cannot contribute to the creation and recycling of elements. So cosmochemists will have to take this concept into account, if it is indeed true, in their models of how elements are formed and distributed across space. They cannot begin to fully understand the chemical evolution of galaxies, including our own, and how quickly the elements needed to form planets. Worldperhaps even with a life of their own made of elements produced by exploding stars that can accumulate.
The results of VFTS 243 were published on May 9 in the journal Physical Review Letters.
