Named SPT0418-47, the galaxy is more organized than expected, casting doubt on the idea that young galaxies are completely chaotic.
Scientists in Germany and the Netherlands have discovered a galaxy similar to the Milky Way at a distance of 12 billion light-years.
The finding is the result of a partnership between the ALMA Observatory in Chile and the European Southern Observatory (ESO), and was published this week in the journal Nature.
The light from SPT0418-47 took more than 12 billion years to reach us, which means that we see it as it was when the Universe was only 1.4 billion years old.
According to scientists, the galaxy is not chaotic like others of its time – and this casts doubt on the idea that galaxies in the early universe were completely chaotic.
“This result represents a breakthrough in the field of galaxy formation, showing that the structures that we observe in nearby spiral galaxies and in our Milky Way were already in place 12 billion years ago,” said astrophysicist Francesca Rizzo, one of the authors of the study.
Although SPT0418-47 does not appear to have spiral arms, it has at least two characteristics typical of the Milky Way: a rotating disk and a group of stars compacted in the middle of the galaxy called “galactic bulge”. This is the first time that such a bulge has been seen in such a young system.
In the early Universe, young galaxies were still forming, so they were believed to be chaotic and without the distinct structures found in more mature galaxies, like ours.
“The big surprise was to find that this galaxy is actually quite similar to nearby galaxies, contrary to all expectations from the models and previous, less detailed, observations,” said co-author Filippo Fraternali.
As the SPT0418-47 is very far away, observing it was a challenge due to the low luminosity and small size. The team overcame this obstacle by using a nearby galaxy as a powerful magnifying glass, allowing ALMA to detect SPT0418-47.
This effect is known as gravitational lensing. It occurs when the gravitational pull of a nearby galaxy distorts and bends light from another, more distant galaxy, causing it to appear warped and enlarged, like a ring of light.
Astronomers then used data from ALMA to determine the shape and movement of gas particles in the galaxy. “When I first saw the reconstructed image of SPT0418-47 I could not believe it: a treasure chest was opening,” Rizzo said.
Simona Vegetti, a co-author of the study, believes that studying this galaxy can help us understand the history of the Universe. “What we found was quite puzzling,” Vegetti said. “Despite forming stars at a high rate, and therefore being the site of highly energetic processes, SPT0418-47 is the most well-ordered galaxy disc ever observed in the early Universe.”