Scientists have discovered strong evidence that some massive stars end its existence with a whimper, not a bang, and dive into a Black hole of their own making without light and fury and supernova.
To understand why this is important, we need to start with a crash course on stellar evolution. Stars generate energy through nuclear fusion processes in their cores by which they convert hydrogen into helium. When stars with at least eight times the mass of our sun When they run out of hydrogen, they start fusion reactions involving other elements instead – helium, carbon, oxygen, etc., until they end up with an inert iron core that requires more energy to put into the fusion reaction than it can handle. produce. At this stage, the fusion reactions cease and the energy production that keeps the star aloft evaporates. Suddenly, gravity has free reign and causes the core to collapse, while the star’s outer layers bounce off the shrinking core and explode outwards—igniting a supernova that can sometimes shine brighter than the entire star for weeks. galaxy.
Meanwhile, the collapsing core forms a compact object. This subject is often spinning neutron star named a pulsar — but under certain conditions it could be a stellar-mass black hole. This is a standard Star timeline story. However, astronomers are now starting to come around to the idea that some stars that produce black holes may do so without supernova explosion.
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Researchers have occasionally noted occurrences failed supernovae – stars that begin to brighten as if they are about to explode, but then falter and disappear. Elsewhere, a study of old photographic plates as part Disappearing and appearing objects during a century of observations (VASCO) project, led by Beatriz Villarroel, found dozens of stars on those old plates that are simply not visible anymore; as if they disappeared without a trace.
Could these failed supernovae and disappearing stars be evidence that the stars have been almost completely pulled into the black hole they form before they get a chance to explode? Maybe, some scientists believe.
“If one stood looking at a visible star undergoing total collapse, at the right time it could be like watching the star suddenly go out and disappear from the heavens,” said Alejandro Vigna-Gómez of the Max Planck Institute. for astrophysics in Germany and declaration. “Recently, astronomers have indeed observed the sudden disappearance of brightly shining stars.”
Although the idea is still only a theory, it now has strong supporting evidence in the form of a strange binary system studied by Vigna-Gómez and his team. The system was designated VFTS 243 discovered in 2022 and resides in the Tarantula Nebula, located in The Large Magellanic Cloud; it contains a star with a mass of 25 and a black hole with a mass of 10 solar rays, which must have been created by a massive star that reached the end of its life relatively recently, cosmically speaking.
“VFTS 243 is an extraordinary system,” said Vigna-Gómez. “Despite the fact that VFTS 243 contains a star that collapsed into a black hole, there is no sign of the explosion.
For example, the orbits of the star and black hole in VFTS 243, around their common center of gravity, are still nearly circular. However, supernova explosions are asymmetric, with slightly more energy produced in one direction than the other, which should give the compact object they form a “natal kick”. Such a kick would accelerate a compact object, causing its orbit to widen and stretch. Usually this kick is between 30 and 100 kilometers (19 and 62 miles) per second, but the black hole in VFTS 243 was kicked at a maximum of just four kilometers (2.5 miles) per second.
The effects of natal kicks have been observed before in pulsars, but never before in stellar-mass black holes. It’s very possible that this tells us something about how stellar-mass black holes form, and VFTS 243 is the clearest look yet at the results of this process.
Natal kicks are the result of three things: debris ejected from an exploding star, an explosion neutrino from the collapsing core of a star and gravitational waves. However, if there was no supernova, there would be no debris, only neutrinos and gravitational waves, which would provide a much smaller kick – which is exactly what we see in VFTS 243.
If this is correct, then it means that many of the most massive stars in the universe, which shine so brightly, end their lives in quiet obscurity as they are pulled into black hole oblivion. This could also be the ultimate fate of the surviving star in VFTS 243 when it reaches the end of its life.
It also has wider implications. A supernova explosion is an element factory. Not only that, elements like oxygen, carbon and nitrogen in the outer layers of the dying star are blasted away space where they can be recycled into the next generation of stars and planets, the intense heat and energy of the supernova shock wave can result in the formation of even heavier elements in the supernova debris. For example, one of the reasons why supernovae shine so brightly for so long is that the radioactive decay of the nickel isotopes produced in the explosion leads to the formation of cobalt and iron.
However, if some massive stars completely collapse into black holes without supernova explosions, then they cannot contribute to the creation and recycling of elements. So cosmochemists will have to include this concept, if it is indeed true, in their models of how elements form and spread through space. Only then can they begin to fully understand the chemical evolution of galaxies, including our own, and how quickly the elements needed to form planets like Earthperhaps even with its own life made from elements produced by exploding stars, it can accumulate.
The findings from VFTS 243 were published on May 9 in the journal Physical Review Letters.