V404 Cygnus, an X-ray binary star that hosts a low-mass black hole, has a wide echelon with a tertiary companion at least 3,500 astronomical units (AU) away from the inner binary, according to MIT astrophysicists. It is said to be part of a triple star.
V404 SIGNI. Image credit: Verge others., doi: 10.1038/s41586-024-08120-6.
V404 Cygni is located approximately 7,800 light-years away in the constellation Cygnus.
This system first attracted attention more than 80 years ago, during the 1938 nova explosion.
Another eruption occurred in 1989 and was discovered by the Japanese X-ray satellite Ginga and high-energy instruments aboard the Mir space station.
The 1989 explosion, known as Nova Cygnus 1989, was pivotal in the study of black holes.
Until then, astronomers had known of only a handful of objects that could be black holes, and V404 Cygnus was one of the most likely candidates.
V404 Cygnus is known to host a central stellar-mass black hole in the act of consuming a small star that spirals very close to the black hole every 6.5 days. This is a configuration similar to most binary star systems.
But new research suggests there's a second star orbiting the black hole, albeit much further away.
“Most black holes are thought to be formed by violent explosions of stars, but this discovery helps cast doubt on that,” said Kevin Burge, a researcher at the Massachusetts Institute of Technology (MIT). Ta.
“This system is very interesting for the evolution of black holes, and also raises the question of whether triples exist.”
Artist's impression of V404 Cygnus: The central black hole (black dot) is consuming a nearby star (orange object on the left), while the second star (white flash at the top) is far away orbiting a distance of Image credit: Jorge Lugo.
Burge and his colleagues estimate that the third companion star orbits the V404 Cygnus black hole every 70,000 years.
The fact that black holes appear to exert a gravitational pull on distant objects raises questions about the origins of black holes themselves.
Black holes are thought to be formed by violent explosions of dying stars. This is a process known as a supernova, in which a star releases a huge amount of energy and light in one final burst before collapsing into an invisible black hole.
But the team's findings suggest that if the newly observed black hole had originated from a typical supernova, the energy released before it collapsed would have kicked loosely bound objects around it. It suggests that it might have been.
So the second outer star shouldn't be hanging around yet.
Instead, the authors believe that the V404 Cygnus black hole formed through a more gentle process of direct collapse, in which the star simply collapsed and formed the black hole without a final, dramatic flash. I think it might be.
Such a benign origin poses little impediment to loosely bound, distant objects.
Because V404 Cygnus contains a very distant star, this suggests that the black holes in this system were born through a more gradual, direct collapse.
And while astronomers have observed more violent supernovae for centuries, this triple system may be the first evidence of a black hole formed from this more gentle process.
In addition to providing clues about the black hole's origin, the outer star also revealed the age of the system.
Astrophysicists observed that the outer star happened to be in the process of becoming a red giant, a stage that occurs at the end of a star's life.
Based on this star's evolution, they determined that the outer star was about 4 billion years old.
Considering that the neighboring stars were born at about the same time, they conclude that the components of the binary star are also 4 billion years old.
“This has never been done before with old black holes,” Dr. Burge says.
“Thanks to this discovery, we now know that V404 Cygnus is part of a triple star. It may have formed by direct collapse, and it formed about 4 billion years ago.”
of findings Published in this week's magazine nature.
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KB barge others. The black hole low-mass X-ray binary V404 Cygnus is part of a wide triple. naturepublished online October 23, 2024. doi: 10.1038/s41586-024-08120-6
Source: www.sci.news
