The galaxy GS-NDG-9422, set among a backdrop of stars and neighboring galaxies. (Image credit: NASA)
The James Webb Space Telescope (JWST) has made an extraordinary discovery, spotting a galaxy that could provide crucial insights into the evolution of the universe. This galaxy, named GS-NDG-9422 (or simply 9422), is located in the early universe and was observed just one billion years after the Big Bang. What makes it truly fascinating is its unusual feature: its gas clouds shine brighter than its stars.
Typically, stars are the most luminous objects in galaxies, but in 9422, it’s the surrounding gas clouds that steal the spotlight. This phenomenon occurs because massive stars in the galaxy are emitting intense light particles, called photons, which heat the gas clouds and make them outshine the stars. This rare occurrence was previously only a hypothesis in galaxies containing some of the oldest generations of stars, but 9422 seems to embody this unique trait. These findings were published in the October issue of Monthly Notices of the Royal Astronomical Society.
Lead researcher Alex Cameron, an astronomer at the University of Oxford, was thrilled by the unexpected discovery. "My first thought in looking at the galaxy's spectrum was, 'that's weird,' which is exactly what the Webb telescope was designed to reveal: totally new phenomena in the early universe that will help us understand how the cosmic story began," Cameron said.
Astronomers have long debated when the very first stars started clumping together to form the galaxies we see today. Many scientists believe that this process began slowly within a few hundred million years after the Big Bang. However, the exact types of stars that formed in the early universe, and how long it took them to ignite, remain mysteries.
The first stars, known as Population III stars, are thought to have been massive, incredibly bright, and extraordinarily hot. Since the Big Bang only produced hydrogen and helium, these stars consisted of just those two elements. But, due to their enormous size and heat, Population III stars burned out quickly, ending their lives in powerful supernova explosions. These explosions scattered heavier elements, paving the way for future generations of stars and the formation of planets.
In their quest to uncover more about these early stars, researchers used JWST to explore deep regions of space. Because light travels at a fixed speed, the farther we look into the universe, the further back in time we can see. This is how astronomers were able to spot galaxy 9422, whose stars are burning at a blistering 140,000 degrees Fahrenheit (80,000 degrees Celsius). These stars are nearly twice as hot as those found in our local universe.
However, despite their extreme temperatures, these stars are unlikely to be part of the original Population III stars. Researchers discovered chemical elements in the galaxy that go beyond hydrogen and helium, suggesting that 9422 is composed of later-generation stars. "We know that this galaxy does not have Population III stars, because the Webb data shows too much chemical complexity," explained Harley Katz, a cosmologist at the University of Oxford. "However, its stars are different than what we are familiar with — the exotic stars in this galaxy could be a guide for understanding how galaxies transitioned from primordial stars to the types of galaxies we already know."
Now that astronomers have found these "missing-link" stars, they are eager to search more regions of the early universe to determine how common these stars are. This could provide vital clues about the universe's earliest stages and help answer long-standing questions about galactic evolution.
Cameron emphasized the excitement of this discovery, saying, "It's a very exciting time, to be able to use the Webb telescope to explore this time in the universe that was once inaccessible. We are just at the beginning of new discoveries and understanding."
