The first galaxies may have formed earlier than predicted

"One way or another, the Universe has managed to form galaxies faster and earlier than we thought," said Tommaso Treu, professor of astronomy at UCLA University.

One of the main missions of the James Webb telescope, which is in its fifth month of observations, is to study the first galaxies formed after the Big Bang, which occurred 13.8 billion years ago.

Based on elaborate cosmological models, scientists thought "it would take time" to find them, said astrophysicist Jeyhan Kartaltepe.

However, in just a few months, James Webb has already identified many new young galaxies, including one that existed only 350 million years after the Big Bang - 50 million years less than the previous one. observed record.

"It's a surprise that there are so many that formed so early," commented Jeyhan Kartaltepe.

Besides their number, one thing amazed scientists: their high luminosity.

"We immediately draw the conclusion that they are massive, and this raises a real enigma: how could they have formed so many stars in such a short time?", summarized Garth Illingworth, from the University of California at Santa Cruz.

To be able to do that, "these galaxies would have to have started forming maybe only 100 million years after the Big Bang," he explained.

"Nobody would have believed that the dark ages would have ended so soon".

An alternative hypothesis would be that these galaxies actually harbor so-called population III stars, very different from those we know.

These very first stars, extraordinarily bright, have so far only been theorized, not observed.

The incredible capabilities of the James Webb telescope have also revealed the appearance of some of these galaxies.

"Our team was struck to be able to measure the shape of these early galaxies," said Erica Nelson of the University of Colorado, quoted in a NASA statement.

"Their quiet, orderly disks challenge our understanding of how the first galaxies formed, in a chaotic young Universe."

The exact distance of these young galaxies - including the one that broke the record - will have to be confirmed in the future thanks to spectroscopic analyses, also carried out with James Webb.

But anyway, thanks to this new observatory, "we are really on the right track to realize this dream of understanding the galaxies of the first ages", marveled Garth Illingworth.

© 2022 AFP