Astronomers Debate Webb's Little Red Dots as Black Hole Stars or Early Black Holes

Two Webb telescope surveys of distant objects included little red dots and observed them for hours at a time. Astronomers tabulated precisely what shades of light were coming from each dot and how bright those shades were. The key spectral finding was that the colors of hydrogen were smeared out across multiple shades. Such an effect usually means observers are looking straight at an exposed black hole, because black holes whip hydrogen clouds around them at furious rates and the clouds emit slightly different colors depending on their speed.

In the spring of 2025, teams led by de Graaff and Naidu unveiled the two strangest dots yet, Quanta reported. The objects could not literally be stars because they were far too bright, and they did not look much like black holes, which have an assortment of ringlike structures at different temperatures. Naidu and de Graaff concluded that they were seeing the first examples of something that combined the vigor of a black hole with the outward appearance of a star: a black hole star.

In that model, the black hole would pull gas around it, dramatically heat it and push light and energy outward, keeping the outer layers of hydrogen from collapsing inward. The black hole would thus form the engine of the star, analogous to the fusion-powered core of the sun. "We are seeing the seed," Naidu said. "This is the birth of potentially every massive black hole in the universe."

Quanta said astronomers have spent the past year in a lively debate about what is really happening. Phys.org reported this week that simulations on the Japanese Supercomputer ATERUI III have explained the nature of the little red dots without requiring exotic assumptions, by conducting the most detailed cosmological simulations yet of conditions in the early universe.

The simulations found that the little red dots are black holes growing at a rate that would be impossible today because of conditions in the early universe. In that era, intense far-ultraviolet radiation from nearby galaxies suppresses star formation in gas clouds, so instead of forming many small stars, the gas can form a single supermassive star that then collapses into a black hole seed. Once formed, these black hole seeds are surrounded by dense gas disks. That environment traps radiation and enables the black holes to grow dozens of times faster than would be possible in the modern universe. The simulated properties of these rapidly growing black holes provide a good match to the little red dots observed by JWST.