They rule out the need to delay the Big Bang date

The first images provided by the JWST telescope (James Webb Space Telescope) sent a small shock through the world of cosmology two years ago: too many big, bright galaxies had formed too close to the Big Bang. Some of these galaxies seemed to have grown so big and so fast that simulations couldn’t explain them, and some researchers suggested that meant something was wrong with the standard model of cosmology. What if we’d gotten the numbers wrong and had to delay the age of the universe?

While there is nothing more exciting in science than an observation that doesn’t fit with theory, this time the waters appear to be returning to normal and there is a rational explanation for the anomaly, according to a new study published Monday in the journal Astrophysical Journal Led by Katherine Hvorowski of the University of Texas at Austin, some of these early galaxies are much less massive than they first appeared. Hvorowski finds a possible reason for the confusion: On the one hand, black holes in some of these galaxies make them appear much brighter and larger than they actually are. On the other hand, the relationship between light and mass in the young universe may have changed, so the observations would still fit the cosmological model.

One aspect that the new paper highlights is that galaxies that appear too massive likely contain black holes that are rapidly gobbling up gas. Friction in the fast-moving gas emits heat and light, making these galaxies much brighter than they would be if that light came only from stars. According to the authors, this extra light could cause the galaxies to contain many more stars, and therefore more mass, than we would otherwise estimate. When the scientists exclude these galaxies, nicknamed “little red dots” (due to their red color and small size), from the analysis, the remaining early galaxies are not too massive to fit the predictions of the Standard Model.

We still see more galaxies than expected, although none of them are massive enough to destroy the Universe.

Katherine Hworowski
— University of Texas at Austin researcher and study leader

“We still see more galaxies than predicted, although none of them are massive enough to break “The universe,” explains Hworowski. “Ultimately, there is no crisis from the standpoint of the standard model of cosmology,” adds Stephen Finkelstein, co-author of the study and director of the CEERS study (Cosmic Evolution Early Edition Science) of the JWST telescope, which produced the data. “Any time you have a theory that has stood the test of time for many years, you need some kind of hard evidence to disprove it. And that’s not the case,” he notes.

Too many massive galaxies

While they have solved the main problem, a less thorny one remains: The JWST data on the early universe still contain about twice as many massive galaxies as expected from the standard model. One possible reason could be that stars formed more quickly in the early universe than they do today. “Perhaps galaxies were better at turning gas into stars in the early universe,” Khvorovsky says.

Star formation occurs when hot gas cools enough to succumb to gravity and condense into one or more stars. But when the gas is compressed, it heats up, creating outward pressure. In our region of the universe, the balance of these opposing forces tends to slow down the star formation process. But perhaps, according to some theories, because the early universe was denser than it is today, it was harder to eject gas during star formation, allowing the process to proceed more quickly.

A mystery with unsolved edges

For an astrophysicist Hector VivesAccording to a researcher at CEFCA (the Centre for Research in Space Physics in Aragon), who was not involved in the study, it appears that these galaxies were biasing the observations towards higher masses, with adjustments to star formation parameters serving as an explanation for the more extreme results. “The light from the accretion disk of a supermassive black hole can dominate the brightness of a galaxy and make it difficult to calculate the number of stars, and therefore their mass,” he explains. “In this study, they rule out cases where this happens and see that although galaxies appear brighter than expected in the early Universe, after small adjustments they are consistent with our models.”

Sara Cazzoli, a researcher at the Institute of Astrophysics of Andalusia (IAA), believes that the results of the paper do not solve the mystery of the evolution of galaxies in the early stages of the Universe. “However, it lays the foundation for future studies on larger samples,” he says. “They should be accompanied by important information, for example, from spectroscopic data on the stellar population.” In his opinion, the results can be used to improve the modeling of the early Universe, which is still very unknown. “It is interesting how quickly knowledge about the populations of these ‘red dots’ is growing thanks to the latest results from the JWST data,” he emphasizes.

“This study clarifies the difficulty of simply interpreting data from very distant galaxies for which we do not have very precise information,” says Isabel Marques, an astrophysicist at the Astrophysical Institute of Andalusia (IAA-CSIC). “In fact, although they continue to see more massive galaxies than the model indicates, some of the adjustments are quite consistent with the models.” This could come from the assumption that the relationship between baryonic matter (the atoms that make up the visible universe) and dark matter was different in the early universe, the specialist explains, or from the even simpler possibility that the transformation between mass and light was different.

“Today in our Universe we know very well what mass corresponds to each type of star, and using this data and the amount of light, we can calculate the mass. These researchers say that perhaps the transformation between light and mass for different types of stars happened differently in the early Universe.” “All this could be solved if we had some way of imaging these primitive and distant galaxies with even greater resolution, which would allow us to analyze the spectrum and solve the puzzle,” he summarizes. “But they lack light because they are faint galaxies. It would be necessary to measure its light at different wavelengths, but this is not yet possible, but I think this is what will happen in the future with large space telescopes,” he says.

There is no need to change the model

“Our work that we have published offers new information in favor of an explanation that does not require a radical change in the cosmological model,” explains Spanish astrophysicist Pablo Arrabal Haro, co-author of the paper, to elDiario.es. “For more than a year now, those of us who have dedicated ourselves to this have come to the consensus that the excess of bright galaxies in the early Universe is due to the fact that some physical phenomena were different at that time in the Universe, but this does not require a different cosmological model.”

The excess of bright galaxies is due to various physical phenomena in the Universe at this time, but does not require a different cosmological model.

Pablo Arrabal Haro
— Astrophysicist and co-author of the article.

For the specialist, the initial idea of ​​the need to change the cosmological paradigm was a sensational exaggeration that quickly turned out to be unnecessary. “This result reveals some physical mechanisms that contribute to the fact that less massive galaxies were brighter in the early times of the Universe compared to later times,” he points out. And although the problem of an excess of bright galaxies still exists, he admits, “we are already able to implement various physical effects that solve the problem, but now we have to check which of these processes actually occur during the first few years.” hundred million years and in what proportion. – This is the main problem now.