SPT0418-47 is gravitationally lensed by another galaxy, giving our telescopes an evil Eye or Sauron look.
ALMA (ESO / NAOJ / NRAO) / Rizzo et al.
Twelve billion years ago, then all space was just an adult baby universe, a young galaxy reminiscent of the Milky Way was fire to life deep in the cosmos. Astronomers have often thought of this early universe as a chaotic, extreme environment where galaxies are unstable and violent. New research suggests that the assumptions may be wrong, and provide new insights into how galaxies form.
In a new study, published Wednesday in the journal Nature, observations made by Chile’s Atacama Large Millimeter / Submillimeter Array (ALMA) of SPT – S J041839–4751.9, or SPT0418-47 for short, show that the child galaxy has features that are similar to those of our own modern Milky Way. Light from the galaxy took 12 billion years to reach us. This means that astronomers look back in time to a galaxy that formed less than 1.5 billion years after the birth of the universe.
Earlier modeling and observations have led astronomers to theorize that the period after the birth of the universe was tumultuous. Early galaxies probably merged into one another and fused to form large, mistrusted masses of stars. They should not be placed in clean, flat discs. But SPT0418-47 does that, and that’s quite a surprise that evokes some of our beliefs about early cosmic activities in the universe.
“This result represents a breakthrough in the field of galaxy formation, showing that the structures we observe in nearby spiral galaxies and in our Milky Way were already 12 billion years ago,” said Francesca Rizzo, an astronomy Ph.D. student at the German Max Planck Institute for Astrophysics and first author on the study, said in a statement.
Because SPT0418-47 is so far away, it is difficult to find in the sky because the light is so fleeting. To find and characterize SPT0418-47, the research team took advantage of a phenomenon known as “gravity lensing.” Light from distant galaxies does not travel in a straight line to Earth – it is affected by the effects of gravity on its way here. Narrow galaxies disrupt and shape the light of distant galaxies as it travels to our telescopes.
But lensing can help detection. Using the technology and the ALMA telescope, researchers were able to magnify the light of SPT0418-47 and stimulate the resolution to observe the functions of the young galaxy. The effect of the lens means that images obtained by ALMA show SPT0418-47 as an aggressive, bright Eye or Sauron-type ring, a perfect light circuit with hundreds of thousands of stars.
Using computer modeling techniques, the research team took the gravitational lenses, round images of SPT0418-47 and reconstructed what the galaxy would look like if our telescopes were powerful enough to see so far on their own (as the video below proves). The modeling changed the galaxy in a surprising way.
“When I first saw the reconstructed image of SPT0418-47, I could not believe it,” Rizzo said. “A treasure chest was opened.”
The reconstruction showed that SPT0418-47 does not have the large, spiral arms we are used to seeing in the Milky Way, but it does have a disk and a giant hump in the center that is reminiscent of our galaxy of house. The European Southern Observatory suggests it is a radiant Milky Way.
“It’s less of a lookalike and more of 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% of the mass of the Milky Way and half of its size.”
But what it lacks in stature makes it out in stellar power. The galaxy’s star formation is equal to the mass of 350 of our own senses, which Martell calls ‘enormous’. By comparison, she notes, the star formation of the Milky Way is just 1.6 solar masses per year. Simona Vegetti notes that the star formation rate is “quite surprising”, because it means the galaxy as a site of very energetic processes. In all likelihood, this would lead to more anxiety, but SPT0418-47 stays cool and calm even with all that activity.
The young galaxy will not evolve into a Milky Way-type spiral galaxy like the one we are used to today. Instead, researchers believe it will become an elliptical galaxy like Messier 87, where the first images of a black hole were captured. Such a fate will not occur for millions of years. However, when the European Southern Observatory’s Extremely Large Telescope goes online in 2025, astronomers are likely to find more of these ordered galaxies, enabling them to discover how they could form and evolve in the early universe.
