Astronomers have found a galaxy “surprisingly” like our own Milky Way – further away than any before.
The galaxy is 12 billion light-years away, meaning that our image of it comes from when the universe was relatively young, at just 1.4 billion years old.
As such, it offers a way of looking back at galaxy formation in the early universe, when it was only 10 per cent of its current age. But scientists were puzzled to find that it was far more similar than expected.
Galaxies from so early in the universe were expected to be turbulent and unstable, in line with existing theories about galaxy formation. But the newly-discovered one was not nearly as chaotic as predicted.
That surprising discover could, in turn, lead to a new understanding of how galaxies form and what processes could have been happening in the early universe.
“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,” says co-author Filippo Fraternali, from the Kapteyn Astronomical Institute, University of Groningen in the Netherlands.
When the researchers looked at the newly-discovered galaxy known as SPT0418-47, they saw that it had features that are characteristic of our own Milky Way. It had a rotating disc and a large group of stars around its middle, which scientists refer to as a “bulge”, and which has never been seen before so early in the universe.
“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 Francesca Rizzo, from the Max Planck Institute for Astrophysics in Germany, in a statement.
The galaxy is so far away that it is difficult to see even with the most powerful telescopes ever created. But the team were able to examine it by using an effect called gravitational lensing, where the universe itself acts as a magnifying glass and allows scientists to see deep into the universe.
As such, it appeared to scientists who viewed it through the Atacama Large Millimeter/submillimeter Array, or ALMA, as a nearly perfect ring of light around the nearby galaxy that functioned as a lens. When it was reconstructed using computer modelling techniques that allowed them to see its true shape, astronomers say they were unable to believe what they found.
“What we found was quite puzzling; 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,” said co-author Simona Vegetti, also from the Max Planck Institute for Astrophysics. “This result is quite unexpected and has important implications for how we think galaxies evolve.”
Scientists now hope to conduct further observations to understand how typical such very young but very similar galaxies might be, elsewhere in the early universe.
The new paper, ‘A dynamically cold disk galaxy in the early Universe’, is published in Nature today.