A prototypical barred spiral galaxy, NGC 1672 in the constellation Dorado. Its spiral arms. like those of ceers-2112, do not twist all the way into the centre, but are attached to the two ends of a straight bar of stars enclosing the nucleus. Credit: Stocktrek Images/ Getty Images.
Most massive disk galaxies in our region of the Universe, including our own Milky Way, have a stellar bar at their centre, which scientists believed could form only in the late stages of galaxies’ lives. But a new study1 on the most distant (and thus ancient) barred galaxy ever observed reveals that this shape can appear during a galaxy’s infancy. The newly discovered object, named ceers-2112, dates back to nearly 11.7 billion years ago, and according to current astrophysics models, its bar should only have formed 2 billion years later. Because its mass is similar to the one that the Milky way would have had at the same time, ceers-12 represent the most ancient progenitor of our galaxy ever found.
“Our discovery was possible thanks to the James Webb Space Telescope, which allows to observe the far universe with high resolution,” explains Luca Costantin, an astrophysicist at the Astrobiology Center in Madrid, and first author of the study, which also involved scientists from the University of Padova and Italy’s National Institute for Astrophysics.
“When we looked at the first images of the galaxy, we did not see the bar structure,” Costantin recalls. “Clues of it came from the superposition of seven different images, captured by filters reaching very long wavelengths,” which are typical of stars far away in the universe. The authors estimated that the stars in ceers-2112 have a total mass nearly four billion times the mass of the Sun, similar to the mass the Milky Way would have had when the Universe was the same age.
However, theoretical simulations of the evolution of galaxies in the local Universe do not predict barred galaxies at that age of the Universe, unless they are much more massive than ceesr-2112, Costantin explains. He adds that they are now trying to understand whether increasing the mass resolution of the simulations could change their conclusions.
Otherwise, the observation of ceers-2112 would lead to revise our understanding of the formation of bars in galaxies like our Milky Way. Bars form when stellar orbits in a spiral galaxy become unstable and deviate from a circular path. “Knowing if these dynamic effects were already in place when the universe was so young could shed light on how the various galaxies’ structures formed,” Costantin concludes.
