James-Webb may have discovered unexpected massive galaxies in the early universe

Normally, the rule is: the more massive a galaxy, the longer it took to form. Except that recent discoveries by the James-Webb telescope could well upset current theories on the formation of massive galaxies and models of the early universe.

Huge galaxies formed very quickly

The space telescope has indeed observed a population of very massive galaxies which would have formed at a much faster rate than predicted by astronomers, between 500 and 700 million years only after the Big Bang which occurred 13.8 billion years ago. of years.

In concrete terms, the James-Webb telescope (JWST) has observed, thanks to its NIRCam instrument and its powerful infrared vision, this little-known region of the very young, and therefore very distant, Universe. He discovered six galaxies much more massive than expected. These galaxies exceed the mass of 10 billion Suns, one of them even exceeding 100 billion. This brings the latter closer to our Milky Way, in a much more compact and much younger version. These galaxies would therefore have formed 20 times faster than ours.

“The theory tells us that at those early ages the galaxies were very small and grew very slowly.explained Ivo LabbĂ©, one of the authors of the study published in Nature. You would typically expect them to be 10 to 100 times smaller in terms of the amount of stars.”. But they are on the contrary very populated, and one of them would contain up to 100 billion stars.

Measures to be confirmed

“These objects are much more massive than expected.adds Joel Leja, professor of astronomy at Penn State and co-author of the study. “We only expected to find tiny, young, baby galaxies at this point, but we have discovered galaxies as mature as ours in what was previously thought to be the dawn of the universe.”

For the moment, these galaxies are considered as candidates and the observations will have to be confirmed. The document published in Nature is therefore subject to change. Scientists are enthusiastic, but remain cautious as long as spectroscopy measurements, in particular to see what light is made of, do not validate or invalidate their observations.

If we are to believe The Conversationthe JWST was already targeting one of the six candidate galaxies a month ago, and it turned out that it was actually a distant baby quasar.

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