Astronomers using the Atacama Large Millimeter/Submillimeter Array (ALMA), partnered with the European Southern Observatory (ESO), has discovered an extremely distant and therefore very young galaxy that is remarkably similar to our own Milky Way. The galaxy is so far away that it took light over 12 billion years to reach us: we see it as it was when the universe was only 1.4 billion years old. Its appearance contradicts the theory that all galaxies in the early Universe were turbulent and unstable. This unexpected discovery challenges our understanding of how galaxies form, giving new insights into the past of our universe.
Although the galaxy SPT0418-47 studied by astronomers does not appear to have spiral arms, it has at least two features typical of our Milky Way: a rotating disk and a bulge, a large group of stars densely packed around the galactic center. For the first time in the history of the Universe, a bulge has been observed, making SPT0418-47 similar to the most distant Milky Way. This makes the distant and young galaxy very similar to ours, which is much “older”.
The big surprise for scientists was that this galaxy is actually very similar to neighboring galaxies, contrary to all expectations from models and previous, less detailed observations, scientists emphasize. In the early universe, young galaxies were still in the process of forming, so the researchers expected them to be chaotic and lack the crisp structures typical of more mature galaxies like the Milky Way.
The study of distant galaxies such as SPT0418-47 is fundamental to our understanding of galaxy formation and evolution. This galaxy is so far away that we were able to see it when the universe was only 10% of its current age – it took light from SPT0418-47 12 billion years to reach Earth. Studying it, we go back to the time when these young galaxies were just beginning to develop.
Because these galaxies are so far away, detailed observations with even the most powerful telescopes are nearly impossible, as the galaxies appear small and dim. The team overcame this hurdle by using a nearby galaxy as a powerful magnifying glass – an effect known as gravitational lensing – that allowed ALMA to peer back into the distant past in unprecedented detail. As a result, the gravitational pull of a nearby galaxy distorts and bends light from a distant galaxy, making it appear warped and magnified.
A distant galaxy with a gravitational lens looks like a near-perfect ring of light around a nearby galaxy due to their near-precise location. The research team reconstructed the distant galaxy’s true shape and gas movement from ALMA data using new computer modeling techniques.
Despite the fact that stars form at a high rate and are therefore the site of high-energy processes, SPT0418-47 is the most ordered galactic disk ever observed in the early universe. This result is quite unexpected and is important for our understanding of the evolution of galaxies. However, astronomers note that although SPT0418-47 has a disk and other features similar to those of the spiral galaxies we see today, they expect this young object to develop into a galaxy very different from the Milky Way. , and will join the class of elliptical galaxies. This is another type of galaxies that, in addition to spirals, inhabit the universe today.
This unexpected discovery suggests that the early universe may not be as chaotic as it was once thought, and raises many questions about how a well-ordered galaxy could have formed so soon after the Big Bang.