James Webb and the impossible galaxies

An international team discovered with James Webb's CEERS images impossible galaxies that shouldn't have formed.
A mosaic collected by James Webb of a region of space near Ursa Major, with inserts showing the location of six new impossible galaxies that formed in the early Universe. Credit: NASA

An international team of astrophysicists has discovered several impossible galaxies hidden in images from the James Webb Space Telescope. Six massive galaxies emerged so early in the history of the Universe that they shouldn’t exist according to current cosmological theory.

Each of the discovered galaxies would have appeared at the dawn of the universe, approximately 500-700 million years after the Big Bang, more than 13 billion years ago. They are very large and contain almost all of the stars currently found in the Milky Way.

A brand new primordial universe

“You just don’t expect the primordial universe to be able to organize itself so quickly. These impossible galaxies, discovered by James Webb, shouldn’t exist because they wouldn’t have had time to form” said Erica Nelson, co-author of the research. Nelson and her colleagues published their results on February 22 in the journal Nature (ref.).

These are not the first galaxies observed by James Webb. Last year, another team of scientists spotted several galaxies that likely merged about 350 million years after the Big Bang. However, those objects were much smaller compared to the new galaxies, as they contained many times less stellar mass.

Researchers need more data to confirm that these galaxies are as large and date back as far in time as they appear. However, their preliminary observations offer an enticing glimpse of how James Webb could rewrite astronomy textbooks. “Another possibility is that these galaxies are a different kind of object, like faint quasars, which would be equally interesting” Nelson reiterated.

James Webb, like Hubble

The recent discovery stems from the Cosmic Evolution Early Release Science (CEERS) investigation of the telescope. These images look deep into a patch of sky near Ursa Major, a relatively unremarkable region of space that the Hubble Space Telescope first observed in the 1990s. Nelson was scrutinizing a postage stamp-sized section of an image when she noticed something strange. Some “blurred points” of light that seemed too bright to be real. “They were so red and so bright. We didn’t expect to see them,” the researcher added.

“It takes time for light to travel from a galaxy to us, which means you’re looking back in time when you look at these objects” she said. “I found this concept staggering. I decided in the moment I grasped it that it was what I wanted to do with my life”. The fast pace of discoveries with James Webb is very similar to the early days of Hubble, Nelson said.

At that time, many scientists believed that galaxies hadn’t started forming until billions of years after the Big Bang. But researchers soon discovered that the primordial universe was much more complex and exciting than they could have imagined. “Even though we’ve already learned the lesson from Hubble, we still didn’t expect James Webb to see galaxies that mature existing so far back in time” Nelson said.

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