At 1.2 billion years old, the galaxy ALESS 073.1 should have the chaotic appearance of a juvenile galaxy: a diffuse group of stars and gas suspended in the early universe. In contrast, this primitive starburst galaxy has a central bulge and a rotating belt that makes it look billions of years older. This strange corner of the universe was recently captured by the Atacama Large Millimeter Array array in Chile.
An international team of astronomers delved into the rapid development of the nascent galaxy in a recent analysis published in the journal Scientific Reports. They found that Aless’s age was less than 10% of the current age of the universe, but some parts of its structure indicate a much older entity. Specifically, the presence of a bulge in the center of the galaxy and a rotating disk surrounding this center, a feature that historians have only seen in galaxies that have had more time to form, on a scale of billions of years.
“The general expectation until a few years ago was that galaxies in the primordial universe had to be very chaotic and turbulent,” Federico Lelli, an astronomer at the Arcetri Astrophysical Observatory in Italy, said in a video call. Lelli, lead author of the new article, began work at the Southern European Observatory in Munich and continued it at Cardiff University. “One would expect to see gas movements that are chaotic. But that is at odds with what we see in this galaxy.”
In the tumult of the primitive universe, the idea was that new stars, and later galaxies, would form from the accretion of gas and material from the interstellar ether. The equipment observed by the Lelli galaxy suggests that the timeline of galactic formation needs to be revisited.
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“To put it in human terms, this galaxy is eight years old, but it looks like a teenager or an adult,” says Lelli saidentifier
The research team did not directly see the bulge, which indicates a density of stars that normally surround a supermassive black hole in the center of a galaxy. Rather, they deduced the presence of the bulge by measuring the movement of gas and dust in the galaxy. The same goes for the rotation of the galaxy, which the team was able to calculate from measurements of gas on either side of the galaxy, indicating that some gas was moving toward the viewer while the gas the other side was moving away.
The bulge could have been produced by a fusion with another galaxy or by an intrinsically unstable galactic structure, although Lelli said the latter is less likely.
“This spectacular discovery challenges our current understanding of how galaxies form because we believe these features only arose in ‘mature’ galaxies, not young ones,” Cardiff University astronomer Timothy Davis said in a statement. of university press.
Although the era of the ALESS rotating disk is not known, its existence at 1.2 billion years still precedes any other known galactic disk.
“Ten years ago we thought disks formed maybe in the middle of the age of the universe,” Lelli said. Since the universe is about 13.8 billion years old, that would be about 6.9 billion years ago. “It simply came to our notice then. The goal post moves and goes back in time. “
ALESS’s observations suggest that there may be more to the formation of other early galaxies than previously thought.
“The question, of course, is to what extent an object like this is common and whether that is the rule or the exception,” Lelli said. “To address this, we plan to observe more galaxies with a similar resolution.”
These observations of other galaxies were supposed to have occurred last year, but the covid-19 pandemic was thwarted. For an observatory like ALMA, which houses hundreds of people in the middle of a desert, the research had to be stopped. Lelli hopes that looking at other galaxies will help contextualize the mature face of ALESS 073.1. With the next one launch of the James Webb Space Telescope and the construction of the extremely large Telescope of the Southern European Observatory, it is fair to say that the future of space observation is bright, as long as we take the time to look.