Researchers have discovered a distant galaxy that has strikingly similar characteristics to our own Milky Way, potentially changing our understanding of how galaxies form.
The galaxy, which has been named REBELS-25, is much more orderly than current science suggests it should be for its age, according to research led by astronomers at Leiden University in the Netherlands.
REBELS-25 is much younger than our galaxy, but already shares its rotation and structure, rather than appearing disordered and chaotic like other early galaxies, researchers said in a statement released Oct. 7.
“Based on our understanding of galaxy formation, we expect most early galaxies to be small and disorderly,” Jacqueline Hodge, an astronomer at Leiden University and co-author of the study, said in the statement.
Early galaxies tend to coalesce and develop smoother shapes incredibly slowly, with our Milky Way taking billions of years to develop ordered structures, the researchers said.
The light reaching Earth from REBELS-25 was emitted just 700 million years after the universe formed 13.8 billion years ago, a surprisingly short time for it to have become so orderly, they said.
“Seeing a galaxy with such similarities to our own Milky Way, which is strongly dominated by rotation, challenges our understanding of how quickly galaxies in the early universe evolved into the orderly galaxies of today’s cosmos,” Lucie Rowland, a PhD student at Leiden University and first author of the study, said in the statement.
The galaxy’s rotation and structure were observed using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in northern Chile.
The team also found data suggesting even more developed features, such as spiral arms, and they plan to conduct more observations to confirm whether they indeed exist.
“Finding further evidence of more evolved structures would be an exciting discovery, as it would be the most distant galaxy with such structures observed to date,” Rowland said.
Andrew Blain, a professor of astrophysics at the University of Leicester who was not involved in the study, said REBELS-25 was “a bit unusual” but “not a revolution.”
Blain highlighted ALMA’s role in finding a real-life example of a type of galaxy that had previously only occurred in simulations.
“Without ALMA there would have been no ability to identify an example, both because individual examples would have been too faint to detect in a reasonable time, and because a large enough sample of candidates could not have been searched,” he told CNN. “ALMA also reveals finer details than previous telescopes.”
Blain said more research is needed before scientists change their understanding of galaxy formation.
“One question would be whether they are very rare, or whether every galaxy goes through a phase like this,” he said. “If they are common, then the models will have to be adjusted.”
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 back then is thought to have been much more chaotic, with galaxy interactions and mergers expected to disrupt the relatively fragile structure of a disk. And yet, that is what REBELS-25 looks like,” he told CNN.
“Is it just a very unusual galaxy, which has led an unexpectedly quiet life up until now, 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.”
The research, which is available as a preprint (a scientific paper that has not gone through the peer review process), has been accepted for publication in the journal Monthly Notices of the Royal Astronomical Society.