Reviewed by Danielle Ellis, B.Sc.Sep 26 2024
Astronomers discovered a unique galaxy, GS-NDG-9422, in the early Universe. This galaxy's gas outshines its stars, a phenomenon never seen before. This discovery could be a crucial step in understanding the evolution of galaxies from the Universe's first stars to the familiar ones seen today. The research was published in the Monthly Notices of the Royal Astronomical Society.
The newly discovered GS-NDG-9422 galaxy appears as a faint blur in this James Webb Space Telescope NIRCam (Near-Infrared Camera) image. It could help astronomers better understand galaxy evolution in the early Universe. Image Credit: NASA, ESA, CSA, STScI, Alex Cameron (Oxford)
Astronomers claim that the finding of a “weird” and unique galaxy in the early Universe may “help us understand how the cosmic story began.”
Approximately one billion years after the Big Bang, GS-NDG-9422 (9422) was discovered. It was notable for having a peculiar light signature that had never been observed previously, suggesting that its gas was outshining its stars.
According to researchers, the “totally new phenomena” may represent the missing link in the galactic history between the earliest stars in the Universe and the familiar, well-established galaxies, which makes it significant.
This extraordinary class of galaxy was discovered by the $10 billion (£7.6 billion) James Webb Space Telescope (JWST), a collaborative effort by the US, European, and Canadian space agencies designed to look back in time to the origins of the Universe.
My first thought in looking at the galaxy's spectrum was, 'that is weird,' which is exactly what the Webb telescope was designed to reveal: new phenomena in the early Universe that will help us understand how the cosmic story began.
Dr. Alex Cameron, Lead Researcher, University of Oxford
To discuss the unusual facts, Cameron contacted his Coworker and Theorist, Dr. Harley Katz. Together, they discovered that Webb's observations and computer simulations of cosmic gas clouds cooked to the point that the gas glowed brighter than the stars by extremely hot, massive stars were almost exact matches.
It looks like these stars must be much hotter and more massive than what we see in the local Universe, which makes sense because the early Universe was a very different environment.
Dr. Harley Katz, Theorist, University of Chicago
Typical hot, massive stars in the local Universe have temperatures between 40,000 ℃ and 50,000 ℃, or 70,000 to 90,000 ºF. The team claims that stars in galaxy 9422 are over 140,000 ºF (80,000 ºC) in temperature.
The galaxy is thought to be going through a brief period of intensive star formation inside a cloud of thick gas that is giving rise to a significant number of big, hot stars, according to astronomers. The gas cloud is blazing incredibly brightly because it is being struck by so many photons of light from the stars.
Nebular gas outshining stars is not only unusual but also exciting because it is expected in the settings of the first generation of stars in the universe, known as Population III stars.
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.
Dr. Harley Katz, Theorist, University of Chicago
Currently, galaxy 9422 represents a single instance of this stage of galaxy evolution, leaving numerous unanswered issues. Are these circumstances typical of galaxies at this time of day or are they uncommon? What additional information about even earlier stages of galaxy evolution may they provide?
To gain a deeper understanding of the Universe's early stages, specifically the first billion years following the Big Bang, Cameron, Katz, and their research partners are currently selecting additional galaxies to include in this population.
Cameron said, “It is 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.”
Journal Reference:
Cameron, A. J., et al. (2024) Nebular dominated galaxies: insights into the stellar initial mass function at high redshift. Monthly Notices of the Royal Astronomical Society. doi.org/10.1093/mnras/stae1547.