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Researchers have discovered a distant disk galaxy that has surprisingly similar properties to our Milky Way, and it could change our understanding of how galaxies form.
The galaxy, dubbed REBELS-25, is much more organized than current science suggests for its age, according to research by astronomers from Leiden University in the Netherlands.
REBELS-25 is much smaller than our galaxy, but it actually shares its rotation and structure, rather than appearing clumpy and chaotic like other early galaxies, the researchers said in a statement published on October 7.
“According to our understanding of galaxy formation, we expect most early galaxies to be small and chaotic in appearance,” Jacqueline Hodge, an astronomer at Leiden University and co-author of the study, said in the statement.
The researchers said that early galaxies tended to knit together and develop smoother shapes very slowly, with our own Milky Way taking billions of years to develop ordered structures.
They said the light reaching Earth from REBELS-25 was emitted only 700 million years after the universe formed 13.8 billion years ago, a surprisingly short period of time for it to have become so orderly.
“Seeing a galaxy similar to our own Milky Way, which is strongly rotation-dominated, challenges our understanding of how quickly galaxies in the early universe evolved into the galaxies organizing the universe today,” said Lucy Rowland, a doctoral student at Leiden University. The study’s first author said in the statement.
The galaxy’s rotation and structure were observed using the Atacama Large Millimeter/submillimeter (ALMA) telescope in northern Chile.
The team also found data pointing to more advanced features, such as spiral arms, and they plan to conduct further observations to confirm whether they actually exist.
“Finding additional evidence of more advanced structures would be an exciting discovery, because it would be the most distant galaxy in which such structures have been observed to date,” Rowland said.
REBELS-25 is “a little unusual,” but “it’s not a revolution,” said Andrew Blain, a professor of astrophysics at the University of Leicester, who was not involved in the study.
Blaine highlighted ALMA’s role in finding a real example of a type of galaxy that had previously only been produced in simulations.
“Without ALMA, there would have been no ability to identify an example — because individual examples would have been too faint to be detected in a reasonable time, and because a large enough sample of candidates could not be searched,” he told CNN. “ALMA also reveals finer details than previous telescopes.”
Blaine said more research is needed before scientists change their understanding of galaxy formation.
He said: “The question that arises is: Is it very rare, or does every galaxy go through a phase like this?” “If it is popular, the models will have to be modified.”
Dave Clements, a reader in astrophysics at Imperial College London, who was not involved in the study, said it was “quite surprising” to find a galaxy like REBELS-25.
“The universe at that time was thought to be more chaotic, with galaxy interactions and mergers expected to disrupt the relatively fragile structure of the disk. However, this is what REBELS-25 looks like.”
“Is it just a very unusual galaxy that lived an unexpectedly quiet life up until the time we saw it, or are these observations telling us that the early stages of galaxy formation don’t work the way we think? At this point we don’t know.”
Search, it is available as Preprint (Paper not subject to peer review), accepted for publication in the Monthly Notices of the Royal Astronomical Society.
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