Physicists discover the first "triple black hole"

Oct. 23 () –

In a study published in Naturephysicists at MIT and Caltech report that they have observed a “triple black hole” for the first time, expanding the concept that these astrophysical objects can encompass.

The new system contains a central black hole that is consuming a small star that spirals very close to the black hole every 6.5 days, a configuration similar to that of most binary systems. But surprisingly, a second star also appears to be orbiting the black hole, albeit at a much greater distance. Physicists estimate that this distant companion orbits the black hole every 70,000 years.

The fact that the black hole appears to have a gravitational pull on such a distant object raises questions about its origin. Black holes are thought to form from the violent explosion of a dying star, a process known as a supernova, by which a star releases an enormous amount of energy and light in a final burst before collapsing and becoming a hole. invisible black.

However, the team’s discovery suggests that if the newly observed black hole is the result of a typical supernova, the energy it would have released before collapsing would have ejected any loosely bound objects in its surroundings. The second star, the outermostI shouldn’t keep going around.

SOFT ORIGIN

Instead, the team suspects that the black hole formed through a gentler process of “direct collapse,” in which a star simply collapses in on itself, forming a black hole without a dramatic last flash. Such a smooth origin would hardly disturb any distant, loosely knit object.

Since the new triple system includes a very distant star, this suggests that the system’s black hole was born through a smoother, more direct collapse. And although astronomers have observed more violent supernovae for centuries, the team says the new triple system It could be the first evidence of a black hole that formed from this gentler process.

“We believe that most black holes form from violent explosions of stars, but this discovery helps cast doubt on that,” he says. in a statement study author Kevin Burdge, a fellow in the MIT Department of Physics. “This system is super exciting for black hole evolution, and also raises questions about whether there are more triplets out there.”

The discovery of the triple black hole occurred almost by chance. The physicists found it while consulting Aladin Lite, a repository of astronomical observations, collected from telescopes in space and around the world. Astronomers can use the online tool to search for images of the same part of the sky, taken by different telescopes that are tuned to different wavelengths of energy and light.

To analyze the discovery in depth, the researchers turned to Gaia, a satellite that has accurately tracked the movements of all the stars in the galaxy since 2014. The team analyzed the movements of the inner and outer stars over the last 10 years of Gaia data and discovered that the stars moved exactly in tandem, compared to other neighboring stars.

They estimated the odds of this type of tandem movement to be about one in 10 million. “This is almost certainly not a coincidence or an accident,” warns Burdge. “We are seeing two stars that follow each other because they are linked by a weak rope of gravity. Therefore, it has to be a three-pronged system.”

How could the system be formed then? If the black hole arose from a typical supernova, the violent explosion would have ejected the outer star long ago. “Imagine you’re pulling a kite, and instead of a strong string, you’re pulling a spider web,” Burdge says.

“If you pull too hard, the fabric will tear and you’ll lose the kite. Gravity is like a barely tied string that’s really weak, and if you do something drastic with the inner binary, you’ll lose the outer star.”

However, to really test this idea, Burdge ran simulations to see how such a triple system could have evolved and preserved the outer star. At the beginning of each simulation, he introduced three stars (the third was the black hole, before becoming a black hole). It then ran tens of thousands of simulations, each with a slightly different scenario of how the third star could have become a black holeand subsequently affected the movements of the other two stars. For example, he simulated a supernova, varying the amount and direction of the energy it emitted.

He also simulated direct collapse scenarios, in which the third star simply collapsed in on itself to form a black hole, without emitting any energy.“The vast majority of simulations show that the easiest way to achieve this triple work is through direct collapse,” Burdge declares.

In addition to providing clues to the origin of the black hole, the outer star has also revealed the age of the system. Physicists noted that the outer star is in the process of becoming a red giant, a phase that occurs at the end of a star’s life. Based on this stellar transition, the team determined that the outer star is about 4 billion years old. Since neighboring stars are born at about the same time, the team concludes that the black hole triplet is also 4 billion years old.

“We’ve never been able to do this with an ancient black hole before,” Burdge concludes. “We now know that V404 Cygni is part of a triplet, which could have formed from a direct collapse and formed about 4 billion years ago, thanks to this discovery.”