The James Webb Space Telescope (JWST) has made an intriguing discovery: a galaxy in the early universe where the gas outshines the stars. This unusual galaxy, named GS-NDG-9422 (9422), was observed just one billion years after the Big Bang and is filled with massive stars burning at nearly twice the temperature of those found in our local universe. These exotic stars are bombarding the surrounding gas clouds with an immense amount of light particles (photons), causing the clouds to heat up and become brighter than the stars themselves – a rare phenomenon hypothesized to exist in galaxies containing the oldest generations of stars.
The researchers behind this discovery, led by Alex Cameron, an astronomer at the University of Oxford, published their findings in the October issue of Monthly Notices of the Royal Astronomical Society. Cameron remarked, “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.”
The discovery of 9422 opens a window into the early universe, a period when the very first stars were coalescing into galaxies. While astronomers have previously estimated that this process began slowly during the first few hundred million years after the Big Bang, they have been unsure about the types of stars that formed during this period and the time it took for them to ignite. The initial stars, known as Population III stars, are believed to have been extremely massive, incredibly bright, and extremely hot, formed from the only materials emitted by the Big Bang: hydrogen and helium.
These colossal cosmic furnaces, while blazing with intense light, also burned out quickly, exploding in supernovae that scattered heavier elements, the building blocks for planets and future generations of stars.
To find evidence of these primordial stars, the JWST was pointed at a distant region of the sky. Since light travels at a fixed speed, looking deeper into the universe allows us to peer further back in time. This is how the astronomers spotted galaxy 9422, revealing stars burning at temperatures of 140,000 degrees Fahrenheit (80,000 degrees Celsius), nearly twice as hot as the stars in our local universe.
Despite their scorching heat, these stars are likely not part of the first generation of stars. The JWST data showed signs of elements beyond hydrogen and helium, indicating that these stars were not the very first stars that formed. Harley Katz, a cosmologist at the University of Oxford, explained, “We know that this galaxy does not have Population III stars, because the Webb data shows too much chemical complexity. 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.”
This discovery is a significant step forward in understanding the evolution of galaxies and the origins of the stars we see today. The JWST is now focusing on other regions of the early universe, hoping to find more of these unique galaxies and better understand their role in shaping the cosmos. “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,” said Cameron. “We are just at the beginning of new discoveries and understanding.”
