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. Credit: NASA, ESA, CSA, STScI, Alex Cameron (Oxford). Public Domain.
The James Webb Space Telescope has helped astronomers identify a ‘weird’ galaxy that is outshining its stars.
The discovery of the weird and unprecedented galaxy in the early Universe could help us to understand how the cosmic story began.
GS-NDG-9422 (9422) was found approximately one billion years after the Big Bang and stood out because it has an odd, never-before-seen light signature – indicating that its gas is outshining its stars.
The ‘totally new phenomena’ is significant, researchers say, because it could be the missing-link phase of galactic evolution between the Universe’s first stars and familiar, well-established galaxies.
This extreme class of galaxy was spotted by the $10bn (~£7.6bn) James Webb Space Telescope (JWST), a joint endeavour of the US, European and Canadian space agencies, which has been designed to peer back in time to the beginning of the Universe.
Lead researcher Dr Alex Cameron, of the University of Oxford, said: “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 reached out to colleague Dr Harley Katz, a theorist, to discuss the strange data.
Working together, their team found that computer models of cosmic gas clouds heated by very hot, massive stars, to an extent that the gas shone brighter than the stars, was nearly a perfect match to Webb’s observations.
Katz, of Oxford and the University of Chicago, said: “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.”
This comparison of the Webb data with a computer model prediction highlights the same sloping feature that first caught the eye of lead researcher Alex Cameron. The bottom graphic compares what astronomers would expect to see in a ‘typical’ galaxy, with its light coming predominantly from stars (white line), with a theoretical model of light coming from hot nebular gas, outshining stars (yellow line). Credit: NASA, ESA, CSA, Leah Hustak (STScI). Public Domain.
Intense star formation
In the local Universe, typical hot, massive stars have a temperature ranging between 70,000° to 90,000° Fahrenheit (40,000° to 50,000° Celsius). According to the team, galaxy 9422 has stars hotter than 140,000°F (80,000°C).
The researchers suspect that the galaxy is in the midst of a brief phase of intense star formation inside a cloud of dense gas that is producing a large number of massive, hot stars. The gas cloud is being hit with so many photons of light from the stars that it is shining extremely brightly.
In addition to its novelty, nebular gas outshining stars is intriguing because it is something predicted in the environments of the Universe’s first generation of stars, which astronomers classify as Population III stars.
Katz said: “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.”
At this point, galaxy 9422 is one example of this phase of galaxy development, so there are still many questions to be answered: Are these conditions common in galaxies at this time period, or a rare occurrence? What more can they tell us about even earlier phases of galaxy evolution?
Cameron, Katz, and their research colleagues are now identifying more galaxies to add to this population to better understand what was happening in the Universe within the first billion years after the Big Bang.
Camerson said: “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.”
The study is published in the Monthly Notices of the Royal Astronomical Society.
