A ‘Naked’ Black Hole from Shortly After the Big Bang: James Webb’s Discovery Challenges Universal Theories

Pushing the limits of what we thought possible, astrophysicists from the Kavli Institute for Cosmology of the University of Cambridge, in collaboration with the Cosmic Frontier Center of the University of Texas in Austin, identified a massive black hole in a primitive galaxy, dated 700 million years after the Big Bang. The data, from the James Webb space telescope (JWST), were analyzed in two additional studies, available on Arxiv, revealing a cosmic structure whose composition and mass challenge current galactic training models.

A black hole disproportionate in a tiny galaxy

Astronomers observed a gigantic black hole located more than 13 billion light years, that is to say, as it was only 700 million years after the Big Bang. This discovery is surprising, because the current models provide that black holes appear later, after the formation of the first stars and galaxies. Now here, this black hole seems to exist before a real galaxy has been formed around him.

The object observed, named QSO1, is in a tiny galaxy barely detectable, despite the power of the JWST. However, the black hole it shelters reaches a mass of about 50 million times that of the sun. This means that it is more massive than the galaxy itself, which is exactly the opposite of what is observed in the nearby universe, where black holes represent only a small fraction of the mass of galaxies.

This disproportion intrigues researchers. Professor Roberto Maiolino (University of Cambridge), quoted by the Guardiantalks about a “practically naked” black hole, without the massive galaxy which should normally accompany it. The data shows that the gas that surrounds this black hole turns so quickly that it can only be retained by a huge mass. This is how the researchers were able to calculate the mass of the black hole, despite its extreme distance.

This observation raises a central question: how did such a massive object have existed so early in the history of the universe, while nothing, in current theories, provided for such a possibility?

Chemical indices that exclude stellar formation

When astronomers examined the light emitted by the gas around QSO1, they made another surprising discovery. This gas is almost completely virgin of metals. In astronomy, the “metals” designate all the heavier elements than hydrogen and helium, such as oxygen or carbon. However, these elements can only exist if stars have lived, burned their fuel, then exploded in supernovas.

But here, as Hannah Uebler, a researcher at the University of Cambridge and co -authority of the study explains, the observed gas contains less than 1 % of the quantity of oxygen present in our sun. This means that no generation of stars seems to have enriched this region. Which is extremely rare, especially around such a massive black hole, according to Space.com.

The analysis of the spectral lines has also revealed that the emitted light does not correspond to the usual radiation of a region full of stars. A particular line, called [OIII]is surprisingly weak. On the other hand, another, Hβ, linked to the activity of the black hole, is very present. This reinforces the idea that the black hole remains active, but alone, without a star to accompany it.

These data, obtained with the JWST NIRSPEC instrument, makes it possible to assert that the region around QSO1 is chemically very primitive. However, in classic models, a solid black hole is formed in an environment where the stars are already numerous. Here, it's the opposite. The black hole is there, active, even before the galaxy was really built.

Classic explanations cannot follow

To understand where a black hole as massive and isolated as QSO1 comes from, scientists have tested several scenarios. None gives a completely satisfactory answer. Usually, we think that black holes are formed when a very massive star explodes and leaves behind a collapsed nucleus. This nucleus becomes a “black seed”, which then grows by attracting gas.

But this process is slow. It is limited by a phenomenon called the Eddington limit. It defines the maximum speed at which a black hole can feed on gas. If this limit is exceeded, the radiation produced repels the gas instead of attracting it. It would therefore take hundreds of millions of years to reach the 50 million solar masses observed for QSO1. However, the universe was only 700 million years old at that time.

Another idea is based on the concept of “black hole by direct collapse”. A huge cloud of gas would collapse without forming a star, giving birth to a solid black hole from the start. But as Roberto Maiolino points out, this scenario requires very precise conditions: a pure gas, an absence of stellar light, and a very stable environment. Simulations show that these conditions remain rare and unstable.

Finally, some models propose that black holes can grow faster than expected, in “Super-Eddington mode”. Nevertheless, this implies the presence of huge quantities of gas, which would normally end up forming stars. This is not the case here … All these models fail to explain both the high mass of the black hole, its galactic isolation, and the chemical poverty of its environment. We must therefore consider another, more radical origin.

The hypothesis of primordial black holes is gaining ground

Faced with these contradictions, the researchers turn to an ancient idea, long considered marginal: the primordial black holes. This hypothesis proposes that certain black holes have formed just after the Big Bang. Not from stars, but from extreme fluctuations of density in the emerging universe. These “bumps” in the matter would have been so compact that they would have collapsed directly into black holes, without going through a stellar phase.

According to Lewis Prole, a researcher at the University of Maynooth, these primordial black holes could then grow quickly by merging between them or by attracting gas, long before the appearance of the first stars. This scenario would explain why certain black holes, such as QSO1, are also massive and as early.

Another advantage: these black holes would be formed in a completely virgin environment, exactly like that observed around QSO1. They may even have served as attraction nuclei for the training of the first galaxies.

The authors argue that this scenario is currently intended to be the most consistent with JWST data. Even if it is still indirect. To have final proof of it, other black holes of this type should be detected at even older ages. Or observe signatures of gravitational waves from their mergers, which could allow future detectors like Lisa.

In the meantime, QSO1 appears as a serious candidate for the status of a primordial black hole. He could thus mark a turning point in our understanding of the first stages of the universe.