Observations from the James Webb Space Telescope suggest the presence of enormous stars in a distant early universe galaxy. These potential Population III stars could reach masses up to 10,000 times that of the sun. The findings may explain the origins of supermassive black holes.
The James Webb Space Telescope has enabled astronomers to scrutinize distant galaxies from the early universe, revealing unusual chemical signatures in some. In galaxy GS 3073, researchers led by Devesh Nandal at the Harvard-Smithsonian Center for Astrophysics identified exceptionally high nitrogen levels, far exceeding those explainable by typical stars or cosmic events.
Nearby stars appear limited to around 120 solar masses, as models of galaxy evolution assume. "All of our evolution models of the galaxies… rely on the fact that stars cannot be more massive than 120 solar masses or so," Nandal noted. However, Population III stars—hypothesized primordial giants—could grow to 1,000 to 10,000 solar masses and produce excess nitrogen, according to simulations. Nandal's team calculated that a few such stars could account for GS 3073's nitrogen abundance. "Our work shows the strongest evidence to date of Population III supermassive stars in the early universe," he stated.
High nitrogen has appeared in other distant galaxies, but GS 3073's levels stand out. Skeptics, including Roberto Maiolino at the University of Cambridge, argue that the galaxy's chemical maturity suggests a non-pristine environment unsuitable for Population III stars. John Regan at Maynooth University countered that early universe galaxies often exhibit bizarre traits, making such formations plausible.
If confirmed, these stars could clarify how supermassive black holes emerged early in cosmic history, providing a rapid growth pathway from massive stellar collapses. Verification remains challenging, requiring additional signatures. "Strengthening the argument for their existence is flat-out hard—it's very hard for us to have a smoking gun signature," Regan said, adding, "But this signature is very strong."
The findings appear in The Astrophysical Journal Letters (DOI: 10.3847/2041-8213/ae1a63).