NASA’s James Webb Space Telescope finds evidence of missing link to first stars

Using NASA’s James Webb Space Telescope astronomers have discovered a galaxy with a strange light signature, which could be its gas outshining its stars. Found approximately one billion years after the Big Bang, galaxy GS-NDG-9422 (9422) could be a missing link phase of galactic evolution between the universe’s first stars and more well-established galaxies.

“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,” said lead researcher Alex Cameron from the University of Oxford.

Strange light signature from Galaxy

Cameron worked with Harley Katz, a theorist, to discuss the data. By working together, the team found that computer models of the cosmic gas clouds heated by hot, massive stars, to the extent that the gas would shine brighter than the stars, was a fantastic match for the telescope observations.

“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,” said Katz, of Oxford and the University of Chicago.

In the local universe, typical massive stars are between 40,000 to 50,000 degrees Celsius. According to the research team galaxy 9422 has stars which are hotter than 80,000 degree Celsius.

The team suspects that the galaxy is in the midst of a phase of star formation inside of a cloud of dense gas producing many massive hot stars. The gas cloud is being hit with large quantities of photons of light from the stars, so it is now shining brightly.

Nebular gas outshining stars is interesting as it is something predicted in the environments of the universe’s first generation of stars, which scientists classify 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,” said Katz.

Unanswered questions

Galaxy 9422 is an example of this phase of galaxy development, so many of the team's questions are still left unanswered. Are the conditions common in galaxies at this time period, or are they rare occurrences? What could they tell us about earlier phases of galaxy evolution? Cameron, Katz and their research team are actively identifying more galaxies to add to this population so they can better understand what could have been happening in the universe within the first billion years after the Big Bang.

“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,” Cameron said. “We are just at the beginning of new discoveries and understanding.”

Source of the news:

Cameron, A.J., Katz, H., Witten, C., Saxena, A., Laporte, N. and Bunker, A.J. (2024). Nebular dominated galaxies: insights into the stellar initial mass function at high redshift. Monthly Notices of the Royal Astronomical Society, [online] 534(1), pp.523–543. DOI: https://doi.org/10.1093/mnras/stae1547