In a new study published Wednesday in the journal Nature, observations of the Chilean Atacama Large Millimeter / Submillimeter Array (ALMA) from SPT-S J041839–4751.9, or SPT0418-47 for short, show that the infant galaxy shares features similar to our own more mature ones Milky Way. It took the light of the galaxy 12 billion years to reach us. This means that astronomers are looking back in time to a galaxy that formed less than 1.5 billion years after the universe was born.
Previous modeling and observations have led astronomers to theorize that the time after the universe was born was turbulent. Early galaxies likely smacked into each other and merged into large, disordered masses of stars. You shouldn’t settle in neat, flat slices. But SPT0418-47 does, and this is quite a surprise that turns some of our beliefs about early cosmic activities in the universe upside down.
“This result represents a breakthrough in the field of galaxy formation and shows that the structures that we observe in nearby spiral galaxies and in our Milky Way were already there 12 billion years ago,” said Francesca Rizzo, Ph.D. Student at the German Max Planck Institute for Astrophysics and first author of the study, said in a statement.
With SPT0418-47 so far away, it is difficult to pinpoint in the sky because the light is so dim. To find and characterize SPT0418-47, the research team used a phenomenon known as “gravitational lenses”. Light from distant galaxies doesn’t travel in a straight line towards Earth – it is affected by the effects of gravity on its way here. Nearby galaxies distort and reshape light from more distant galaxies as it travels towards our telescopes.
However, lenses can aid detection. Using the technology and the ALMA telescope, the researchers were able to enlarge the light from SPT0418-47 and increase the resolution to observe the features of the young galaxy. The effect of the lens action means that images obtained from ALMA show SPT0418-47 as an aggressive, fiery ring of the Sauron type, a perfect circle of light with hundreds of thousands of stars.
Using computer modeling techniques, the research team captured the circular gravitational images from SPT0418-47 and reconstructed what the galaxy would look like if our telescopes were powerful enough to see that far for themselves (as shown in the following video). The modeling has reshaped the galaxy in surprising ways.
“When I first saw the reconstructed image from SPT0418-47, I couldn’t believe it,” said Rizzo. “A treasure chest opened.”
The reconstruction showed that SPT0418-47 does not have quite the large spiral arms that we are used to in the Milky Way, but a disk and a huge bulge in the middle that is reminiscent of our home galaxy. The European Southern Observatory suggests it is a Milky Way galaxy.
“It’s less of a doppelganger than a mini-me,” says Sarah Martell, an astrophysicist at the University of New South Wales who was not involved in the study. “It’s only 25% the mass of the Milky Way and half the size.”
But what he lacks in stature, he makes up for in star power. The galaxy’s star formation rate corresponds to the mass of 350 of our own suns, which Martell calls “enormous”. For comparison: the star formation rate of the Milky Way is only 1.6 solar masses per year. Simona Vegetti states that the rate of star formation is “quite puzzling” as she describes the galaxy as a place of high-energy processes. Presumably this would create more clutter, but SPT0418-47 remains cool and calm despite all of these activities.
The young galaxy will not develop into a spiral galaxy of the Milky Way type as we know it today. Instead, the researchers believe it will become an elliptical galaxy like Messier 87.. Such a fate will not occur for millions of years. However, when the extremely large telescope of the European Southern Observatory goes online in 2025, astronomers are likely to find more of these ordered galaxies in an attempt to figure out how they might form and evolve in the early universe.