The first sister of the Milky Way

sDisk galaxies with spiral arms, such as our own Milky Way, have a bar-shaped structure in their central region in about two-thirds of the cases. The Milky Way also has such a bar, although it can only be properly seen from Earth using infrared space telescopes that can see through interstellar dust. Until now, there was reason to believe that such barred galaxies could only evolve when the universe had already passed 4.2 billion years of its current 13.8 billion years of age. Before that, simulations of galaxy evolution suggested that still-young stellar islands were too turbulent to form bars.

But now a team led by Madrid astronomer Luca Costantin has published in the journal “Nature” the observation of a barred galaxy with the catalog name “Ceers-2112”, whose light made its way to us when the universe was only two billion years old. The discovery is the result of a measurement campaign called Cosmic Evolution Early Release Science (CEERS) using the NIRCam infrared camera on board the James Webb Space Telescope. The galaxy, with its bar and mass of 3.9 billion solar masses, would likely have been very similar to the appearance of the Milky Way at that time. Through observation, the researchers concluded that bars in galaxies form over about 400 million years, and that the first ones could have come into existence as early as 1.15 to 1.5 billion years after the formation of the universe.