The galaxy ALESS 073.1, which is 1.2 billion years young, should have the chaotic radiance of a youthful galaxy – a young, diffuse group of stars and gas floating in the early universe. Instead, this primal starburst galaxy has a central bulge and a spinning belt that make it look billions of years older. This strange corner of the universe was recently imaged by the Atacama Large Millimeter Array in Chile.
An international team of astronomers delved into a recent analysis of the rapid development of the nascent galaxy published in the journal Scientific Reports. They found that the age of ALESS is less than 10% of the current age of the universe, but parts of the structure indicate a much older entity. Specifically, the presence of a bulge in the center of the galaxy and a rotating disk surrounding that center is a feature that astronomers have historically only seen in galaxies that have taken longer to form, on the scale of billions of years.
“Until a few years ago, the common expectation was that galaxies in the primordial universe would be very chaotic and turbulent,” said Federico Lelli, an astronomer at the Arcetri Astrophysical Observatory in Italy, in a video call. Lelli, lead author of the new paper, started work at the European Southern Observatory in Munich and continued it at Cardiff University. “You would expect gas movements to be chaotic. But this is contrary to what we see in this galaxy. “
In the tumult of the early universe, the idea was that new stars, and later galaxies, would form from the growth of gas and material from the interstellar aether. The observed team of the galaxy Lelli suggests that the timeline of galactic formation should be revisited.
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“To put it in human terms, this galaxy is about 8 years old, but it looks like a teenager or an adult,” says Lelli saID card.
The research team did not see the bulge directly, indicating a density of stars typically surrounding a supermassive black hole in the center of a galaxy. Instead, they deduced the presence of the bulge by measuring the movement of gas and dust in the galaxy. The same is true of the rotation of the galaxy – which the team was able to find from gas measurements on either side of the galaxy, indicating that some gas was moving towards the viewer while gas was leaving the other side.
The bulge could have resulted from a fusion with another galaxy or from an inherently unstable galactic structure, although Lelli said the latter is less likely.
“This spectacular discovery challenges our current understanding of galaxy formation, because we believed that these features only occurred in ‘adult’ galaxies, not young ones,” said study co-author Timothy Davis, an astronomer at Cardiff University, in a press release. from the university.
Although the age of the rotating disk of ALESS is unknown, its existence still predates every other known galactic disk at 1.2 billion years.
“Ten years ago, we thought that discs may have formed in the mid-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. “And now we are at 10%. The goalpost moves back and forth in time. “
ALESS’s observations suggest that the formation of other early galaxies may involve more than previously thought.
“The question, of course, is how often an object like this occurs, and whether this is the rule or the exception,” said Lelli. “To address this, we plan to observe more galaxies with a similar resolution.”
Those sightings of other galaxies were supposed to take place last year, but the Covid-19 pandemic got in the way. For an observatory like ALMA, where hundreds of people live in the middle of a desert, research had to be postponed. Lelli hopes looking at other galaxies will help contextualise the adult occurrence of ALESS 073.1. With the forthcoming launch of the James Webb Space Telescope and the construction from the European Southern Observatory’s Extremely Large Telescope, it’s fair to say that the future of space observation is bright, as long as we take the time to look.