Young stable galaxy detected by scientists contradicts theories suggesting that early galaxies were chaotic
A distant Milky Way-like galaxy has provided scientists a glimpse of our universe's formative years. Their observations raise two questions: was the early cosmos chaotic as once thought and, if it was, how long it remained that way?
Theories have suggested that the universe was created from chaos. "Galaxies in the early universe are expected to be the site of powerful phenomena like supernova [when stars end their lives] explosions which release a lot of energy," Dr Simona Vegetti, from the Max Planck Institute for Astrophysics, and the co-author of the study told MEA WorldWide (MEAWW). They were expecting to see cosmic gas moving chaotically in winds, and not swirling in the center. They were neither expecting to see distinct features typically seen in mature galaxies.
Instead, the researchers saw a relatively stable galaxy. Observations from Atacama Large Millimeter/submillimeter Array (ALMA) -- a telescope sitting in Chile -- showed that it was not enveloped in chaos as previously thought. It had already developed some distinct features, including a disc -- a flattened circular volume of stars. It also had a bulge, another structure, which was expected to form much later, co-author Filippo Fraternali, from the Kapteyn Astronomical Institute, the University of Groningen in the Netherlands, told MEAWW. Bulge is used to describe tightly packed stellar bodies in the central region.
The galaxy in question is SPT0418-47, whose light took 12 million light-years to reach Earth. In other words, scientists are viewing it when the Universe was just 1.4 billion years old. Currently, the age of our cosmos is 13.8 billion years. The researches set out to understand the features of very distant, and therefore, very young galaxies. "Because these galaxies are very far, it is challenging to study them in great detail using current telescopes. They are not powerful enough," Dr Vegetti explained.
To get around this problem, astronomers used a technique called gravitational lensing. They used a relatively closer galaxy to help magnify their distant targets. "In practice, we look for a pair of galaxies that are far away from each other but appear aligned to us. It’s like observing through a much more powerful telescope," she said.
Next, the team fed their data into computer software to reconstruct the shape of the distant galaxy. "When I first saw the reconstructed image of SPT0418-47, I could not believe it: a treasure chest was opening," said Francesca Rizzo, a graduate student from the Max Planck Institute for Astrophysics in Germany and the lead author of the study. Vegetti added that despite the high rates of star formation in the galaxy, SPT0418-47 is the most well-ordered galaxy disc ever observed in the early Universe.
The reconstructed image showed a near-perfect ring in the sky. "This result shows that early galaxies are less chaotic than expected," Fraternali said. "Another way to interpret it is that the chaotic phase (if present) lasts much less time than was thought."
The study focused only on a single galaxy. Researchers are not sure how prevalent such distant galaxies are. They are hoping to answer this question next. Besides, next-generation telescopes will help experts study more distant galaxies, thereby getting a further peek into the past. "These new facilities will bring this type of analysis to the next level, allowing us to observe even younger galaxies with an even greater level of detail," Fraternali said.
The study is published in Nature.