Fascinating revelation of a ‘twin’ galaxy to the Milky Way challenges theories about the early formation of the Universe

Under the direction of scientists from the CSIC-INTA Astrobiology Center (CAB), an international team of researchers has made a groundbreaking discovery. They have found a ‘twin’ galaxy of our Milky Way, known as a barred spiral, in a place and at a time where it was previously believed such galaxies could not exist. This discovery, made using the James Webb Space Telescope and published in the prestigious journal ‘Nature’, challenges our understanding of the formation and evolution of the first galaxies.

The age of the Universe is 13.76 billion years, and until now, astronomers believed that spiral galaxies like our Milky Way could only acquire their complex and ordered structure after at least 7 billion years since the Big Bang. However, this new discovery proves them wrong.

“Contrary to what was expected,” says Luca Costantin, lead author of the article, “this discovery reveals that galaxies similar to the Milky Way already existed 11.7 billion years ago, when the Universe was only 15% of its current age.” The newly discovered galaxy, named CEERS-2112, is a perfectly formed barred spiral and is located ‘only’ 2 billion years from the Big Bang.

A difficult observation

Studying the evolution of the Milky Way requires analyzing multiple galaxies at different stages of development to reconstruct its own path to maturity. In the nearby Universe, most massive spiral galaxies, including our Milky Way, exhibit an elongated bar-shaped structure in their central regions. However, according to theoretical models, the physical and dynamic conditions of the early Universe should not have allowed the formation of bars in the youngest and most distant galaxies. These galactic bars play a crucial role in galactic evolution by facilitating the mixing of elements necessary for the formation of stars. Scientists suspect that the bar of the Milky Way rotates cylindrically, similar to a toilet paper holder, funneling gas towards the galaxy’s center and triggering bursts of star formation.

“Galaxies have not always been as we observe them around us,” says Pablo G. Pérez González, second signatory of the article. “Their mass and structure vary throughout their life. Although barred galaxies similar to the Milky Way are common in the nearby Universe, until now, we believed that they should be extremely rare when we look back in time.”

A sign of maturity

Until recently, scientists considered the presence of a central bar as a sign of galaxies reaching full maturity, a process that was thought to occur only halfway through the Universe’s evolution. Observations made with the Hubble Space Telescope supported this idea, as they revealed very few barred galaxies in the early Universe.

However, the James Webb Space Telescope’s exceptional capabilities are revolutionizing astrophysics and challenging our expectations of the distant Universe. With its ability to collect six times more light than Hubble, the new telescope can unveil details of distant galaxies that were previously unseen.

“With the James Webb,” explains Cristina Cabello, co-author of the article, “we now have the technology and instruments necessary to study the morphology of very distant galaxies in unprecedented detail. Investigating how galaxies acquire the structures that define them today is crucial for understanding their formation and evolution.”

The discovery of CEERS-2112 demonstrates that barred spirals can evolve in a fraction of the time previously believed. According to Alexander De la Vega, an astronomer at the University of California, Riverside and co-author of the study, this evolution may occur in just a billion years.

Changing Astronomy

This discovery could have significant implications for astronomy in two aspects. “Firstly,” points out De la Vega, “theoretical models of galaxy formation and evolution must now consider that some galaxies become stable enough to host bars at a very early stage in the history of the Universe. These models may need to adjust the amount of dark matter that makes up galaxies in the early Universe, as dark matter is believed to influence the rate at which bars form.”

“Secondly,” continues De la Vega, “the discovery of CEERS-2112 shows that structures like bars can be detected in the very young Universe. This is important because galaxies in the distant past were smaller than they are now, making it challenging to find bars. The discovery of CEERS-2112 paves the way for the detection of more bars in the young Universe.”