Black hole stars

It may look like the glowing sun or a superstar, but it's actually something quite different. For the first time, there's evidence that it's a completely new cosmic object: so-called black hole stars or "quasistars." This discovery brings scientists one step closer to understanding the formation of black holes, which exist in every galaxy.

Researchers tracked down the "quasistars" using the James Webb Space Telescope, the largest and most powerful space telescope ever. Since 2022, the telescope has been observing a thousand mysterious "little red dots": tiny red points of light deep in the universe, about 12 billion light-years away from Earth.

Initially, astronomers thought the red balls were ultra-dense, extremely massive galaxies, giant stars, or enormous black holes that were swallowing matter and emitting large amounts of light. But new research led by the Max Planck Institute for Astronomy in Heidelberg has found "strong evidence" of a new type of celestial object in our early universe: a black hole star.

These giant balls of gas resemble stars, but they aren't. They lack a key characteristic of a star: there's no nuclear fusion, the reason our sun and other stars radiate light and heat.

The extreme brightness of stars is largely due to a massive black hole at the center of the red ball, which devours matter. During this process, some of that matter is converted into energy. This finding is remarkable because it could help explain how supermassive black holes in the early universe could grow so rapidly—a question that has long puzzled scientists.

The bright spot currently being studied differs from other red dots in one respect: it emits an exceptionally large amount of red light, but almost no UV or blue light. Normally, the brightness of each color varies gradually. Researchers therefore refer to it as “a remarkable ruby” or The Cliff. This is a reference to the extremely sharp transition in the light spectrum, which is reminiscent of a ravine or cliff.

A comparison with existing stars and galaxies yielded no results: the properties of The Cliff deviated too much. This led researchers at the Max Planck Institute for Astronomy to conclude that a new model is needed to explain this mysterious red star.

“There is now reasonable consensus on this, although much remains to be investigated,” says Dutch researcher Anna de Graaff, who led the study. “For example, we don't know exactly how much The Cliff weighs and what its precise structure is. It's certainly millions of solar masses, but whether it's one million or ten million is not yet entirely clear.”

Breakthrough

Peter Jonker, professor of astronomy at Radboud University and not involved in the research himself, calls it “a breakthrough.” The discovery brings scientists one step closer to understanding the formation and growth of supermassive black holes.

The findings provide strong evidence for the first time that a supermassive black hole can swallow large amounts of matter at very high speeds, Jonker says. "Previously, there were ideas suggesting this, but now there's concrete evidence." The research shows that black hole stars may have been the precursor to a supermassive black hole.

There are still plenty of questions, Jonker adds. "We know that the supermassive black hole we find in our Milky Way grew in the early universe. But we still know too little about how supermassive black holes form and what influence they have on the galaxy they're in. This seems like a step in the right direction."

The next step in the research is to analyze large numbers of these "little red dots," says De Graaff. "Then we can more clearly show their structure, their mass, how fast they grow, and how important this phase is in the growth of black holes."