Black holes: What if their hearts were not a singularity? Two new theories emerge
Illustration of the distorted space-time of a black hole in rotation, known as Kerr black hole. © generated by Brice Haziza on Bing Creator
Since Astronomers have managed to imaginewe are sure that black holes do exist, despite their strangeness. Their gravitational field is so intense that nothing approaching them too closely can escape, not even light. This is why they are a black shadow in space.
The intensity of their severity is such that space-time diverges, that is to say that the curvature of space tends towards infinity in their center. This is why we are talking about black “hole”. And as the whole matter goes towards a central point, it is of infinite density.
Telling so, it seems almost logical, except that it is not so physically acceptable. Indeed, physicists are generally less lovers of infinite than mathematicians, because the real world does not seem to accommodate endless things, quite the contrary. Since the general relativity of Einstein (1915) and the work of Karl Schwarzschild (1916) have shown that black holes were physically and mathematically possible, many wonder if their singularity is very real.
Modeling of a black hole. © NASA
The problem is that the observation of its interior will be forbidden to us, because when a star collapses to give a black hole, then forms a event horizon which irretrievably separates the outside from inside.
Beyond the horizon, is everything allowed?
A meeting of specialists in the theory of black holes was held in Trieste (Italy) to debate this famous gravitational singularity. They studied two alternative models of black holes: the “regular”, which has no central gravitational singularity, but a green hole) having an horizon of external events, and even a second formed inside. Another candidate, the black hole “Mimicker” (imitator), which would have neither gravitational singularity nor even by the horizon of events.
From left to right: classic black hole, regular black hole without singularity and black hole imitator without singularity or horizon. © Julio Arrechea et al, Arxiv 2025
What allows astrophysicists to consider these alternatives is generally the consideration of quantum effects for which the modeling of severity is still a problem. They even think that these different physical models could be transition phases of black holes, which can then be seen as events rather than finished objects (the gravitational collapse continues until the end of time for an outside observer).
In their Document published on Arxivthe researchers note that these two other models, the regular black hole and the mimicker, must have slightly different signatures of the classic black holes, like irregular gravitational lenses due to the different movements of the photons near the black hole, or gravitational waves of different shape which would make it possible to distinguish a classic black hole from one of their alternative models.
They conclude that the future of these models seems “healthy” to them and that we should learn more in the years to come.
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