Even an instrument as powerful as the James Webb Space Telescope can detect puzzling phenomena at times. It is the case of the multiple red dots that has been found throughout the Universe in recent years. Many of them are a mystery that is difficult to decipher with the technology available. However, thanks to a very propitious physics phenomenon, James Webb himself has managed to enter on one of these little red dots, to find something fascinating. A black hole that goes against known physics, for having formed before the galaxy that houses it.
The data. The black hole in question is enormous, with a mass 50 million times that of the Sun. It is located within a tiny galaxy, called Abell 2744-QSO1, with a diameter of 1,300 light years. To give us an idea, our Milky Way has a diameter of more than 100,000 light years. It is estimated that this galaxy formed 700 million years after the Big Bang, making it very old. However, according to the calculations According to a team of scientists from the Universities of Cambridge and Florence, the black hole could have formed one second after the explosion that gave rise to the Universe.
What came first, the chicken or the egg? If we change the chicken and the egg for the galaxy and the black hole, the answer until now was more or less clear. Not all galaxies have a black hole at their center, but most of them do. Traditionally it has been thought that the black hole was formed when some of the galaxy’s stars ran out of fuel and collapsed. Such a concentration of mass was formed that its gravity began to attract everything that was at a specific distance (the one within its event horizon) and, thus, it fed itself, becoming larger and larger. That is what was believed, but it is a hypothesis that sometimes does not completely add up.
A little red dot with a trick. The system formed by a tiny galaxy and an immense black hole inside makes up one of the red dots detected by James Webb. Most of them are very difficult to analyze, but this one has an advantage that makes it easier to observe. And, between the galaxy and James Webb, there is a galaxy cluster called Abell 2744 (Pandora cluster) that acts as a lens. It is so massive that it bends space-time around it and forms a kind of lens which allows us to see the QSO1 galaxy in a larger size. In very simplified terms, it acts like a magnifying glass. Furthermore, thanks to this same effect, a triplicate image is formed that can be analyzed in more detail.
Primitive black holes. By being able to see these images with a magnifying glass, a tiny galaxy and a huge black hole have been observed, both very old. Generally, the mass of black holes cannot be measured. The calculations are made using assumptions extrapolated from what we know about black holes in the local Universe. Thus, it was calculated that the QSO1 black hole had a mass equivalent to 40 million times that of the Sun. But it did not add up much for such a small galaxy. How could it have become so large by “feeding” only on material from the galaxy itself? All this has been able to be answered, again, thanks to James Webb.
Beyond the magnifying glass. In order to better measure this black hole, the Integral Field Unit (IFU) of the James Webb near-infrared spectrograph. This instrument, instead of focusing on a single point, has the ability to make a 2D map of a region of the sky. Thus, you can track the effects of gravity on the gas that occupies that specific region and even analyze the distribution of different elements in that same gas.
With all this, something interesting has been seen. That the gas rotates around a center in a similar way to how the planets do around the Sun. According to Kepler’s laws, the further away from the center an object orbits, the slower it does so. This is true with the planets, but also with gas. Therefore, the black hole must be very very massive. So far so good. We had already assumed that, but what is its mass?
The calculations of truth. By knowing how fast a gas orbits at a certain distance, you can know the mass of its center. Since the center was the black hole, these scientists only had to do the calculations to know that its mass is equivalent to 50 million suns. Guesses pointed to 40 million, so they were relatively close in astronomical terms. But it is strange, since its mass is equal to two thirds that of the galaxy. It’s too big for that galaxy.
Another interesting fact. Since this James Webb instrument also allows the composition of the gas to be determined, it has been seen that the black hole consists mainly of hydrogen and helium. There is very little oxygen, as would be expected if it had formed solely from the stars of its galaxy. In fact, its metallicity is less than 0.5% that of the Sun. All this data does not fit with a black hole that formed from its galaxy. He had to train before.
The hypotheses. All this points to the fact that the black hole was formed by a direct collapse. But when? That is not so clear, although there are two hypotheses. For one thing, it could have been formed by a heavy seed that originated in the first second of the Big Bang. Or perhaps it was formed a little later, by the collapse of a gas cloud. Either way, this is a great find, since it is about of the first direct measurement of the mass of a black hole within the first billion years after the Big Bang. And the good thing is that it agrees with the assumptions that had been extrapolated from the local Universe.
More red dots. The authors of the two studies that have been published on this research consider that there may be more red dots with details as surprising as this one. We just need to find ways to get into them.
Image | NASA, ESA, CSA, L. Furtak (Ben-Gurion University), R. Maiolino (Cambridge), F. D’Eugenio (Cambridge), I. Juodžbalis (Cambridge), H. Übler (MPE), C. Marconcini (University of Florence). Image processing: A. Pagan
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