Birth of starlight in earliest galaxy merger 13 billion years ago

NASA’s James Webb Space Telescope (JWST) has made a remarkable observation of the earliest galaxy merger in the early universe. The discovery challenges current cosmological theories by indicating faster and more efficient star formation than previously thought.

The galactic merger occurred more than 13 billion years ago – just 510 million years after the Big Bang. The finding is reported in a paper published in Nature Astronomy.

“When we conducted these observations, this galaxy was 10 times more massive than any other galaxy found that early in the universe,” says lead author Dr Kit Boyett from the University of Melbourne.

“It is amazing to see the power of JWST to provide a detailed view of galaxies at the edge of the observable Universe and therefore back in time,” says Professor Michele Trenti, team leader of the ASTRO 3D First Galaxies group at the University of Melbourne. “This space observatory is transforming our understanding of early galaxy formation.”

The astronomers have noted that their observations indicate a merger that was still underway more than 13 billion years ago.

Finding such large and complex structures so early on in the life of the universe raises questions about how galaxies and other objects in the cosmos form.

“Our cosmology isn’t necessarily wrong, but our understanding of how quickly galaxies formed probably is, because they are more massive than we ever believed could be possible,” says Boyett.

The paper is also the first to describe the population of stars making up merging galaxies.

“When we compared our spectrum analysis with our imaging, we found two different things. The image told us the population of stars was young, but the spectroscopy spoke of stars that are quite old. But it turns out both are correct because we don’t have one population of stars but two,” Boyett explains.

“The old population has been there for a long time and what we believe happens is the merger of the galaxies produces new stars and that’s what we’re seeing in the imaging – new stars on top of the old population.”

It is the first time such peaks of new star formation has been seen so early in the universe.

Simulations suggest that objects of this size and age can exist but are extremely rare. That suggests that, either the astronomers were extremely lucky in finding the ancient galactic merger, or the simulations are wrong and such objects are much more common in the early universe.

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