The first galaxies may have formed earlier than predicted

published on Thursday 17 November 2022 at 22.40.

The very first galaxies may have formed earlier than astronomers previously thought, according to early observations from the new James Webb Space Telescope, which have already shaken up scientific understanding of the cosmos in just a few months.

“Somehow, 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 tasks 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 extensive cosmological models, scientists thought “it would take time” to find them, said astrophysicist Jeyhan Kartaltepe.

But 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 short of the previously observed record.

“It is a surprise that there are so many formed so early,” commented Jeyhan Kartaltepe.

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

“We immediately draw the conclusion that they are massive, and this raises a real puzzle: 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 must have started to form maybe only 100 million years after the Big Bang,” he explained. “No one would have thought that the Dark Ages would end so quickly”.

An alternative hypothesis would be that these galaxies actually contain so-called population III stars, very different from the ones 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 amazed 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, ordered disks challenge our understanding of how the first galaxies formed in a chaotic young universe.”

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

But still, thanks to this new observatory, “we are really on the right track to realize this dream of understanding the galaxies of the first ages”, wondered Garth Illingworth.

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