Paris (AFP)

Astronomers have detected a cluster of galaxies with a supermassive black hole at its center dating from the early ages of the Universe, a discovery that helps to better understand the formation of these enigmatic cosmic monsters, according to a study released Thursday.

The scene, seen by the European Southern Observatory (ESO), takes place when the Universe was not even a billion years old, or 10% of its current age (13.8 billion years): six galaxies are trapped in cosmic filaments similar to a spider's web, caught up in a gigantic black hole of a billion solar masses, lurking in the heart of the structure.

These very first black holes, which would have been born from the collapse of the first stars, are "one of the most difficult astronomical objects to understand", comments Marco Mignoli, of the Institute of Astrophysics of Bologna (Italy), author principal of the study published in the journal Astronomy & Astrophysics.

“Before, we thought they were small and that they grew over time, over 13 billion years. But finding them so early in the history of the Universe shows that they have evolved much faster, "astrophysicist Françoise Combes, from the LERMA laboratory at the Paris-PSL Observatory, told AFP.

How is this rapid growth possible?

The study suggests that the immense web of filaments and the galaxies that cluster in it contain enough gas to provide the "fuel" the black hole needs: by devouring the gas from the filaments of the main galaxy - the one that contains it. possesses the most - in the heart of which it lodges, it transforms itself into a cosmic giant in accelerated.

"At the beginning of the Universe, there was much more gas and a much higher density than today", describes Françoise Combes, 2020 CNRS gold medalist.

It is in these "overdense" regions, the filaments, where everything happened more quickly, that such objects may have formed.

With the expansion of the Universe, the gas spread, the filaments diluted.

The Milky Way is located in a much less dense region, which the researcher compares "to the countryside" - its central black hole is "only" four million solar masses - compared to the "large agglomerations" that are the clusters of galaxies .

It is thanks to ESO's Very Large Telescope in Chile (VLT) and its MUSE instrument that these galaxies, among the most difficult to locate, have been observed.

"We think we have only seen the tip of the iceberg, and that these few galaxies discovered around the black hole are only the brightest," concludes Barbara Balmaverde, co-author of the study.

© 2020 AFP