Study Sheds Light on Mystery of Giant Galaxies in Young Universe | Science

When the space telescope two years ago James Webb He began sending back his first images of the universe’s early days, and there were surprises. Instead of tiny galaxies that hadn’t yet had time to grow, there were clusters of giant stars that seemed to challenge the most accepted models of cosmology. Earlier this year, the brightest object in the universe was discovered 12 billion light-years away: a quasar so bright that for decades it was mistaken for the nearest star. Instead of the sun, it was a disk of gas and dust seven light-years across, orbiting a black hole with a mass equal to 17 billion suns.

Back then, a possible explanation was the tendency of the universe to form very massive objects in regions with a high density of galaxies. In the current universe, after billions of years of cosmic expansion, everything is further away from everything else and there is no longer any mass to generate giant objects so quickly. The existence of seed holes, a type of object that could explain how such massive black holes formed so early, was also suggested.

However, a new study published yesterday Monday in Astrophysical Journaloffers an alternative explanation. The brightness of some of these galaxies may not be due to their size or the number of stars they contain, but to the effect of highly active black holes inhabiting their interiors. These objects consume vast amounts of nearby gas, and the friction of this rapidly moving material causes the extraordinary brightness, making them appear more massive than they actually are.

When the scientists excluded these particularly bright galaxies, the masses of the rest fit the predictions of the Standard Model of cosmology. “The point is that from the perspective of the Standard Model of cosmology, there is no crisis,” says Steve Finkelstein, a professor at the University of Texas at Austin and a co-author of the study. “When you have a theory that has stood the test of time like this, you need compelling evidence to disprove it, and this is not the case,” he says.

However, the data James Webb They continue to show more galaxies than would be expected with a formation rate similar to that seen in our region of space, and there is still no clear interpretation of the nature of the small red dots that appear in the space telescope images. The teams like the one who signs the paper in Astrophysical Journal They observed in the spectra of these dots signatures of what looked like hydrogen moving at high speed, which is typical of the accretion disks that form around black holes. If that were the case, this gas falling into the hole would explain, at least in part, the luminosity of these dots, which would not need to contain so many stars. Figuring out how much light comes from moving gas and how much from stars will help us understand what the cosmos was really like a few hundred million years after the Big Bang.

While the new images don’t cause the standard model of cosmology to collapse, it may need some tweaking. “We don’t understand everything very well, and that’s what makes science fun, because it would be really boring if we could explain everything with one scientific paper and there were no more questions to answer,” says Katherine Hworowski, the study’s first author.

In the coming years images James Webb They promise to provide material for rethinking the evolutionary history of the universe, including such mysteries as dark energy, a force that makes up more than 70% of the universe. The telescope’s ability to photograph distant supernovae, a type of star used to measure distances in space, will help better estimate the rate of expansion of the universe throughout its history and compare ancient and modern galaxies. It will also help reconstruct how a huge, omnipresent, invisible energy pushed the universe to its current state.

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