It is formed by a black hole fed by a companion star and that has another more distant star. Most black holes are considered to be formed by powerful explosions of stars. This finding casts doubt on that hypothesis. This is the first triple black hole.
This system is called V404 Cygni. It is within the Milky Way and about 8,000 light years from Earth. It is a binary black hole that has been well studied before. But it is actually part of a triple set.
New hypothesis
Scientists discovered that one of the stars rotates around the black hole with a period of just 6.5 Earth days. The third star makes a complete rotation in 70,000 years. The discovery was the result of long-term observations made with the Gaia space telescope. Follow the movements of billions of stars in our galaxy.
This sparked a new hypothesis about the emergence of black holes. According to her, not everyone emerges from the violent disappearance of big stars. Some are generated silentthat is, without requiring a nuclear explosion.
«Most black holes form from violent explosions of stars. But this discovery helps to cast doubt on it. This system is very interesting for the evolution of black holes. “It raises the question of whether there are more three-pointers out there,” explains study author Kevin Burdge.
He emphasizes that the presence of an external star in the system is surprising. It would have to have been ejected during the formation of the black hole. It was probably formed by direct collapse, a rare phenomenon.
Intertwined
The existence of the second star has been known for decades. But astronomers thought it was simply a relatively nondescript star close to V404 Cygni. However, it travels with V404 Cygni in the same direction and at the same speed. This suggests that the objects are related to each other.
«It is almost certainly not a coincidence or an accident. We are looking at two stars that follow each other because they are linked by this weak rope of gravity. So it has to be a three-pronged system,” says Burdge.
The first triple black hole continues to be studied. One of the biggest questions is whether the shape of the outer star’s orbit is circular or eccentric. To do this, scientists intend to use an instrument called GRAVITY in the Very Large Telescope (European VLT). The study was published in Nature.