Astronomers have discovered a galaxy so big and so old that it shouldn’t exist – at least according to our current understanding of early galaxy formation.
The galaxy, named ZF-UDS-7329, contains more stars than the Milky Way and appears to have formed about 13 billion years ago.
It was spotted with NASA’s James Webb Space Telescope (JWST), an instrument built to observe these types of ancient galaxies and look back at the early eras of the universe.
The remarkable thing about this is that such a large galaxy could not have formed so early in the universe, because dark matter did not yet exist. This means that a galaxy of this size should not have been supported 800 million years after the Big Bang.
Astronomers could not see star system ZF-UDS-7329 clearly before the James Webb Space Telescope was launched. Now they can see that it formed about 13 billion years ago.
Dr. Themiya Nanayakkara, who led the spectral analysis of the JWST data, said: ‘We are now going beyond what was possible to confirm the oldest massive, silent samples found deep in the universe.
‘This pushes the boundaries of our current understanding of how galaxies form and evolve.
‘The most important question now is how they form so quickly, very early in the universe, and what mysterious mechanisms prevent them from abruptly forming stars, while the rest of the universe does.’
Our universe is about 13.8 billion years old, which means ZF-UDS-7329 was formed when the universe was in its infancy, about 800 million years old.
Astronomers have long thought that dark matter is essential for the growth of a galaxy.
Halos of this mysterious substance, they say, formed the seed that supports the center of a galaxy and allows stars to accumulate.
There’s just one problem with ZF-UDS-7329: As far as astronomers know now, dark matter didn’t exist back then, at least not in quantities large enough to support such a massive galaxy.
Nevertheless, this galaxy exists.
It points to “significant gaps in our understanding” of how early stars and galaxies formed, the scientists behind the discovery wrote.
The article describing the galaxy was published in the magazine Nature.
Because of the time it takes for light to travel through the vastness of space, they have shifted by the time they reach Earth.
Astronomers have developed techniques to detect how large this shift is, allowing them to determine that the image captured by JWST is likely about 11.5 billion years old.
The stars likely formed about 1.5 billion years before that, the researchers wrote, meaning the galaxy is about 13 billion years old.
Scientists had been trying to get a clear picture of this galaxy for seven years, but it was so far away and so faint that even Earth’s largest telescopes couldn’t get a clear enough view of it to measure its age.
With the JWST they finally could.
A close-up image of the ZF-UDS-7329 shows its enormous size. The scale bar indicates 2 kiloparsecs, or 6,530 light years.
“The formation of galaxies is largely determined by how dark matter concentrates,” said co-author Claudia Lagos, associate professor of astronomy at the University of Western Australia, in a study. rack.
The way galaxies form is a fundamental area of study in astronomy.
And while it’s difficult to say with absolute certainty what the early universe looked like, modern astrophysicists have built numerous models that use current data to make predictions about it.
One of these predictions, which astronomers often agree on, is that there were fewer and fewer supermassive galaxies the further back in time you go.
If these new observations of ZF-UDS-7329 are accurate, these models are called into question.
“Having these extremely massive galaxies so early in the universe poses a significant challenge to our standard model of cosmology,” Lagos said. ‘This is because we think that such massive dark matter structures that host these massive galaxies have not yet had time to form.
“More observations are needed to understand how common these galaxies are and to help us understand how big these galaxies really are.”
The team’s next steps will be to find more galaxies like this one, to confirm the finding and find answers about how it could have happened.