Astronomy: Probably the first black hole in a triple system raises questions
Another star has now been discovered in a system of star and black hole that has been known for years. It is a novelty that raises another question.
Artistic representation of the system
(Image: Jorge Lugo/MIT)
Almost by chance, a research team from the Massachusetts Institute of Technology (MIT) has discovered the first black hole located in its system of three celestial bodies. The star system is called V404 Cygni and the black hole there has been one of the best researched for years. However, while it was previously assumed that there was only one other celestial body there, a very closely orbiting and slowly disintegrating star, another star was probably always overlooked, MIT announced on Wednesday.
Black hole without supernova?
As the group led by astrophysicist Kevin Burdge explains, the central black hole of V404 Cygni and the star that orbits it once every six and a half days have been known for a long time. Rather by chance, Burdge discovered another star on an image of the system. Using data from ESA's Gaia space telescope, the scientists were able to confirm that the new star moves through space together with the two other celestial bodies. Although it is 3500 astronomical units away from both, together they form a triple system – the first ever known to have a black hole. However, because it is so far away, its existence raises a not insignificant question.
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If the black hole's progenitor star had exploded at the end of its life, it would almost certainly have ejected the extremely distant and therefore only weakly connected third star from the system. This has been confirmed by numerous simulations carried out by the team. The group therefore assumes that the star must have collapsed directly into a black hole without going supernova. If this assessment is confirmed, it would be the first evidence of a so-called "soft" collapse. However, the system would also raise whether there are more such triple systems out there.
The star system is around 8,000 light years away from our Earth and, according to the calculations, the outer star needs 70,000 years to orbit the two inner objects. Because this star is currently undergoing the process of forming a red giant star, the research team was even able to determine that it is probably around four billion years old. As neighboring stars generally form together, the others are likely to be of a similar age. The research work is now presented in the scientific journal Nature.
(mho)
