Astronomers have confirmed the existence of massive, star-like objects powered by black holes at their centers, a discovery that challenges existing models of early galaxy formation and offers a potential explanation for puzzling observations from the James Webb Space Telescope (JWST). These “black hole stars,” as they’re called, appear to have been common in the universe’s first billion years, but no equivalents exist today, suggesting a lost growth mode for supermassive black holes.
The Mystery of Little Red Dots
JWST initially identified a population of unusually bright, compact, and red galaxies—dubbed “little red dots” (LRDs)—that defied easy classification. Theories ranged from densely packed star clusters to supermassive black holes obscured by dust, but neither fully explained the observed light patterns. The LRDs’ spectra did not match either of these phenomena, leaving astronomers baffled.
The Black Hole Star Hypothesis
The emerging consensus suggests that LRDs are massive spheres of gas surrounding central black holes. As matter falls into these black holes, immense gravitational energy is released, causing the surrounding gas to glow intensely—mimicking a star, but far brighter. These black hole stars would have been billions of times brighter than our sun, yet powered by an entirely different mechanism than nuclear fusion.
Evidence Mounts: Spectra and Variability
Recent analysis of over a hundred LRDs reveals that their light spectra closely resemble that of a single, smooth surface—a characteristic of stars. This contrasts with the complex spectra of typical galaxies, which combine light from multiple sources. Furthermore, observed variations in brightness, even when viewed through gravitational lenses (allowing time-delayed observations over decades), align with theoretical models of black hole accretion disks.
“The black hole star model has been around for a while but was thought to be so weird and out there, but it actually does seem to work and make the most sense,” says Jillian Bellovary of the American Museum of Natural History.
Challenges and Future Research
While strong evidence supports the black hole star hypothesis, definitively proving the presence of a black hole at each core remains difficult. The dense gas envelope obscures direct observation, forcing astronomers to rely on indirect measurements such as brightness fluctuations. Further research will focus on detecting characteristic black hole variability patterns and refining models of early black hole growth.
These findings suggest a previously unknown phase in the early universe’s evolution, where black holes may have grown through a fundamentally different process than what we observe today. Understanding the lifespan and contribution of these black hole stars is crucial to reconstructing the formation history of supermassive black holes, which now reside at the centers of nearly all galaxies.
