No one expected them. They weren’t supposed to be there. And now no one can explain how they were formed.
A galaxy about the size of the Milky Way and full of mature red stars appears scattered in deep-field images acquired by the James Webb Space Telescope (Webb or JWST) during an early observing campaign. It’s giving astronomers a headache.
Described in a new study based on Webb’s first data release, these galaxies are so far away that powerful telescopes see them as little red dots. By analyzing the light emitted by these galaxies, the astronomer confirmed that he was looking at galaxies in the infancy of the universe 700 million years from just 500 million years after the Big Bang.
An early galaxy like this isn’t surprising in itself. Astronomers had predicted that the first star clusters appeared shortly after the universe emerged from the so-called Dark Ages.
Related: 12 amazing discoveries made in space by the James Webb Space Telescope
But the galaxies found in Webb’s images were surprisingly large, and those stars were too old. The new findings contradict existing ideas of how the early universe looked and evolved, and do not match previous observations made by Webb’s less powerful predecessor, the Hubble Space Telescope. .
Joel Leja, assistant professor of astronomy and astrophysics at Penn State University and one of the study’s authors, told Space.com: email. “Previous studies of the early universe using Hubble and other instruments tend to find nascent small blue galaxies. These galaxies just formed from the soup of the primordial universe and are themselves nascent galaxies. We’re building stars and structures.”
Young stars are generally bright blue. As it ages, the star glows redder as it burns fuel and cools. In the ancient galaxy Webb created to discover, astronomers never expected to see an old red star. Also, perhaps the Sun didn’t expect to find more than a billion galaxies. But Webb’s reddish dot revealed in deep space looks like he’s 50 times bigger than that, Leja said.
“The heaviest galaxies in our sample are estimated to have mass. [two to four times lower] “This was amazing. We are finding candidates for galaxies as massive as our own galaxy when the universe was 3% of its present age.”
Before astronomers began rewriting cosmological theories to explain how these galaxies rapidly came together after the Big Bang, Leja said the strange red dots they were seeing weren’t different. I said I need to make sure. However, most of the alternative explanations also require entirely new concepts, Leja said.
“For example, stars in the early universe were so deficient in heavy elements that they may have emitted light in exotic ways, and we may not have incorporated them into our models,” Leja writes. “Alternatively, our understanding of how stars form locally, such as how many stars form from gas as a function of stellar mass, does not apply at all to the early universe. “These things are exciting to discover, and they’re also likely to overturn our understanding of star formation in the early universe in a very different way.”
The images revealing these mysterious galaxies were acquired by Webb’s near-infrared camera (NIRCam) as part of the Space Evolutionary Early Emission Sciences (CEERS) program. Astronomers plan to point Webb’s mirror back at these galaxies, this time to capture the light spectra of their distant points. A spectrum decomposes the observed light according to its wavelength composition and reveals the chemical and physical properties of the source.
“Most importantly, the spectrum gives very accurate distances to these objects,” said Leja. “The ‘distance’ and ‘identity’ of these objects are correlated. If we know the distance, we can determine the identity and vice versa. Therefore, the spectrum immediately tells us whether the hypothesis is correct. “
Just over six months after Webb’s team released its first observations from the Great Observatory, scientists are already facing the challenge of rewriting theories about the early universe.
“For the first time, we looked into the very early universe, and we didn’t know what we would find,” Leja said in a statement from Penn University.
“It turns out to have found something so unexpected that it actually poses a problem for science. It calls into question the big picture of early galaxy formation.”
The study was published in a journal Nature Wednesday (February 22nd).
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