Astronomers’ discovery of distant Milky Way-like galaxy challenges our theories of how cosmos evolved

“Seeing a galaxy with such similarities to our own Milky Way, that is strongly rotation-dominated, challenges our understanding of how quickly galaxies in the early Universe evolve into the orderly galaxies of today’s cosmos,” Lucie Rowland, a doctoral student at Leiden University and first author of the study, said in the statement.

The rotation and structure of the galaxy were observed using the Atacama Large Millimeter/submillimeter Array (ALMA) telescope in northern Chile.

The team also found data that hinted at even more developed features, such as spiral arms, and they plan to carry out more observations to confirm whether they in fact 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 paper, said REBELS-25 is “a bit unusual,” but “it’s not a revolution.”

Blain highlighted the role of ALMA in finding a real example of a kind of galaxy that had previously only been produced in simulations.

“Without ALMA there’s been no ability to identify an example – both because individual examples would have been too faint to detect in a reasonable time, and a large enough sample of candidates could not be searched,” he told CNN. “ALMA also reveals details finer than earlier telescopes.”

Blain said more research is needed before scientists change their understanding of galaxy formation.

“A question would be are they very rare, or does every galaxy go through a phase like this,” he said. “If they’re common, then models will have to be tweaked.”

Dave Clements, a reader in astrophysics at Imperial College London, who was not involved in the paper, said it “is quite a surprise” to find a galaxy like REBELS-25.

“The universe back then is thought to be a lot more chaotic, with galaxy interactions and mergers expected to disrupt the relatively fragile structure of a disk. And yet that’s what REBELS-25 looks like,” he told CNN.

”Is it just a very unusual galaxy, that’s led an unexpectedly quiet life up to when we see 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.”