For 60 years, the world of science has tried to prove that all black holes are stable. A French team has just arrived there.

Are black holes stable? If this question may seem trivial, it is actually crucial for the balance of the Universe (just that). Supposed by Albert Einstein in his theory of general relativity, black holes are very real today. But questions still remain around these dark stars.

Kerr black holes, a variety discovered by the eponymous mathematician in 1963, are among the most interesting to study. Contrary to the “classic” so-called Schwarzschild black holes, those of Kerr have a kinetic force (they turn on themselves and move) as well as an electromagnetic charge.

## Black holes like no other

Two very rare arrangements for black holes, but which have posed questions to astrophysicists for half a century. Because this movement and this electromagnetic force suggest that the black hole can be modified by the surrounding events, in short it is not stable. For researchers, the whole point is to know if an activity (whatever it is) is capable of disturbing the black hole or if the latter will “absorb” the energy and return to a past position.

For Jérémie Szeftel, researcher at the University of the Sorbonne, this is indeed the case. In a set of three articles compiling over 2000 pages of information and research, he details the “mathematical proof” of his discovery. This research work was immediately welcomed by the scientific community.

## A study hailed by the scientific community

For Demetrios Christodoulou, mathematician at the Polytechnic School of Zurich: ” *this result is indeed an important step in the mathematical development of general relativity*“. Other researchers like Shing-Tung Yau, a professor at the prestigious American university of Harvard, have praised the work of Szeftel and his team.

Because this problem, many astrophysicists have rubbed shoulders with it without success for years. Its resolution is therefore a small feat in the scientific world. The equations that we had until now regarding the mechanics of black holes only concerned fixed stars.

## Proof by contradiction

In order to succeed in proving that Kerr’s black holes were also fixed, Jérémie Szeftel had the idea of using “proof by contradiction”. This scientific process is regularly used in such cases. Regarding our experience today, Szeftel tried to find the circumstances that would make the black hole unstable.

But despite hundreds of tests in ever more extreme configurations, the equations written by Kerr in 1963 proved to be robust, proving the stability of the black hole. But all the work is not yet done for Szeftel and his team. He indeed succeeded in demonstrating that the slowly rotating black holes were stable, but not the others.

He should therefore go back to work in the next few days, to try to prove that rapidly rotating black holes are also stable. In the event that this is not the case, we will have to review our entire model of the physics of the stars and start a lot of research from scratch.