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James Webb and the Improbable Galaxies

These are just tiny red dots in a massive black sky spotted by the giant James Webb space telescope. After six of them, it was analyzed in A new study published in the journal Nature on Wednesday, January 22, does not seem out of place. Observations that do not fit well with theories of galaxy formation and the Big Bang. So much so that The Guardian called them potential Galaxy Breakers – This means that it can bring to its knees certain models used in astrophysics.

But beware, the published results are to be considered and are not yet final, according to the astrophysicists interviewed by FRANCE 24 as well as the authors of the article.

These six bright red lights in the sky represent several galaxies imaged by the James Webb telescope during one of the first observations made in July 2022. They are part of a group of thirteen galaxies, studied in the Nature article, that reside in the very distant universe and were It could have been born about 600 million years after the Big Bang, more than 13 billion years ago. But the six are the most interesting.

1, 2, 3, 100 billion suns

“We looked directly at the early days of the universe [dans l’univers la distance d’observation est à la fois dans l’espace et le temps, NDLR] Without knowing what we will find. We’ve come across something so unexpected that it contradicts our scientific models, said Joel Lega, an astrophysicist at Penn State University (Penn). In an interview with the American channel CNN.

The group of six galaxies is huge. It exceeds the entire mass of 10 billion suns, while one of them reaches 100 billion suns, “which brings it closer to our Milky Way” which forces it to matter, sums up LeMond.

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To assess the mass, “we observe the light emitted by these galaxies,” notes Mauro Stefanone, an astrophysicist at the Leiden Observatory, one of the co-authors of the article published in Nature. The light comes from stars, and the more galaxies there are, the more massive the galaxy.

And this is where the shoe pinches. Such starry galactic monsters should not have existed near the beginning of our universe, according to the standard model of galaxy creation. “It takes time to collect the material for star formation. And the time scales predicted by the models are rather long,” explains Olivier Bernier, an astrophysicist at the Institute for Research in Astrophysics and Planetary Science.

Massive galaxies like the six that caught the article’s authors’ attention in Nature, “were not yet seen until after the first billion years following the Big Bang,” notes Le Monde.

But this is not the only challenge facing our understanding of the history of the universe through the hypotheses presented in the study. Instead, the red halo of galaxies in images taken by the James Webb Telescope should be blue. “There are two types of red in space observations, one that can tell if an object is far away, and the intrinsic red color of stars that indicates that they are mature objects. In the case of our six galaxies, they all have an intrinsic red color,” explains Mauro Stefanon. In sum, “the color of the young galaxy will be blue while the older galaxy will be red,” asserts François Hammer, an astrophysicist at the Paris Observatory who has just published “Voyage de la Terre aux confines de l’Univers” (ed. Odile Jacob).

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Again, galaxies farther away in space-time should not have had time to develop mature stars.

waiting for spectrometer

At least, if the study authors were not mistaken in their estimates of the distance of these six galaxies. “They are also taking precautions and clearly saying that at this point it is only about candidate galaxies,” emphasizes Olivier Bernier. The next step will be to classify them as pinned galaxies.

These reservations are due above all to the fact that the hypotheses have not yet been submitted to the final judge of the matter: the James Webb Telescope’s NIRSpec spectrometer. This is a contraption that can automatically “fix the spectral shift.” [ou décalage vers le rouge qui correspond aux objets lointains, NDLR] allowing to obtain a more accurate estimation of the distance”, explains François Hammer.

For now, the study authors used a colorimetry method by applying different filters to get an idea of ​​distance. It’s a more literal approach that’s used more frequently, but one whose results need to be taken with more tweezers.

This famous red synonym can also be associated with great distance by other factors. “There are other ways a galaxy can disguise itself in the infrared, especially if its spectrum is reddened by space dust,” says Stéphane Charlot, a specialist in galaxy formation at the Astrophysical Institute in Paris. “Dust really absorbs blue, which means that a very dusty planet will have a redder signature,” adds François Hammer.

It’s also possible that these galaxies are not as massive as they seem, especially “if they contain supermassive black holes,” Mauro Stefanon acknowledges. These phenomena, called “quasars”, “make the gases falling on them radiate so strongly, evoking the signature of stars,” Le Monde confirms. In this hypothesis, it would not take a large number of stars to explain the luminosity of these galaxies.

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“Analysis by spectrometer makes it possible to determine the distance and also remove, if necessary, other possible explanations for the properties of these galaxies. So let’s wait for the results before questioning the physical models,” sums up François Hammer.

Young galaxies with different properties?

But even if this tool confirms the study’s hypotheses, it won’t automatically sign the end of the Big Bang Theory. “It must be understood that the models provide general rules, and that there is room for exceptions. Perhaps these models will have to be improved to take into account these possible novelties,” believes Olivier Bernier.

For him, this new study is also part of a general trend of articles about the first observations of the James Webb Telescope that “suggest that smaller galaxies do not necessarily have the characteristics we attribute to them yet.”

Perhaps from this aspect we should look for an answer to the challenges of this study of the theory of galaxy formation. “There is evidence to suggest that stars formed in the early days of the universe can emit a lot of light without being very massive,” Stéphane Charlotte notes. There are several tracks that show that we are far from understanding everything about the formation of our universe.