Galaxy found in the early universe that shouldn’t exist

Researchers have identified a galaxy that existed when the universe was less than 300 million years old.

This galaxy, known as JADES-GS-z14-0, is not only distant but also surprisingly mature. It defies our expectations about how galaxies formed in the early universe.

NASA’s James Webb Space Telescope (JWST) observed the galaxy, and revealed its unexpected complexity. The research builds on a 2024 discovery that identified JADES-GS-z14-0 as the most distant known galaxy.

The new study focuses on the galaxy’s chemical composition and growth, and offers fresh insights into what occurred during the universe’s first chapter.

An unexpected galaxy discovery

The findings come from the JWST Advanced Deep Extragalactic Survey (JADES), a program designed to study distant galaxies. While astronomers expected to locate faraway objects, this galaxy stood out in surprising ways.

“This wasn’t simply stumbling upon something unexpected,” said Kevin Hainline, an associate research professor at the University of Arizona’s Steward Observatory.

“The survey was deliberately designed to find distant galaxies, but this one broke the team’s records in ways they didn’t anticipate – it was intrinsically bright and had a complex chemical composition that was totally unexpected so early in the universe’s history.”

Galaxies hidden in the early universe

The galaxy’s brightness and extended structure challenge previous assumptions. “It’s not just a tiny little nugget. It’s bright and fairly extended for the age of the universe when we observed it,” Hainline said.

The discovery of JADES-GS-z14-0 suggests that similar galaxies may be more common than previously believed.

“The fact that we found this galaxy in a tiny region of the sky means that there should be more of these out there,” said lead study author Jakob Helton, a graduate researcher at Steward Observatory.

“If we looked at the whole sky, which we can’t do with JWST, we would eventually find more of these extreme objects.”

Mature chemical composition

The team used multiple instruments aboard JWST, including the Near Infrared Camera (NIRCam) and the Mid-Infrared Instrument (MIRI). These tools helped identify substantial amounts of oxygen present in the galaxy – an unexpected finding for a galaxy from such an early cosmic era.

In astronomy, elements heavier than helium are considered metals. These metals form over multiple generations of stars, making their presence in JADES-GS-z14-0 surprising.

The early universe contained only hydrogen, helium, and traces of lithium. The discovery of oxygen suggests the galaxy had been forming stars for around 100 million years before its observation.

A long history of star formation

To create oxygen, the galaxy must have gone through several cycles of star birth and death.

“To make oxygen, the galaxy must have started out very early on, because it would have had to form a generation of stars,” said George Rieke, Regents Professor of Astronomy and the study’s senior author.

“Those stars must have evolved and exploded as supernovae to release oxygen into interstellar space, from which new stars would form and evolve.”

This process indicates that galaxies may have started forming earlier than previously believed, shifting the timeline for the first structures in the universe.

A rare and fortunate observation

Observing JADES-GS-z14-0 required nine days of telescope time, with 167 hours of NIRCam imaging and 43 hours of MIRI imaging. The team focused on a tiny region of the sky, and the galaxy happened to be in just the right spot for MIRI to detect.

“The U of A astronomers were lucky that this galaxy happened to sit in the perfect spot for them to observe with MIRI,” Helton said. “If they had pointed the telescope just a fraction of a degree in any direction, they would have missed getting this crucial mid-infrared data.”

To explain the scale of the observation, Helton provided an analogy: “Imagine a grain of sand at the end of your arm. You see how large it is on the sky – that’s how large we looked at.”

Refining models of galaxy formation

The existence of such a mature galaxy so early in cosmic history provides a valuable test for theories of how galaxies form and evolve.

“Our involvement here is a product of the U of A leading in infrared astronomy since the mid-’60s, when it first started. We had the first major infrared astronomy group over in the Lunar and Planetary lab, with Gerard Kuiper, Frank Low and Harold Johnson,” Rieke said.

These observations allow astronomers to refine their models of galaxy formation, and improve their understanding of how the universe transitioned from its initial elements to the complex chemistry that supports life.

New era of galaxy discovery

The discovery of JADES-GS-z14-0 represents a major step forward in understanding the universe’s infancy. With new technology like JWST, astronomers can explore galaxies that were previously out of reach.

“We’re in an incredible time in astronomy history,” said Hainline. “We’re able to understand galaxies that are well beyond anything humans have ever found, and see them in many different ways and really understand them. That’s really magic.”

The study is published in the journal Nature Astronomy.

Image Credit: NASA, ESA, CSA, STScI

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