Dark stars are a theoretical type of star from the early universe, powered not by nuclear fusion like ordinary stars but by the energy released when dark matter particles collide and destroy each other. First proposed in 2007 by physicist Katherine Freese, graduate student Douglas Spolyar, and physicist Paolo Gondolo, these objects could have grown to enormous sizes, potentially reaching millions of times the mass of our sun. They have never been confirmed to exist, but the James Webb Space Telescope has identified several candidates that match predictions.
How Dark Matter Replaces Fusion
Every star you can see in the night sky is powered by nuclear fusion, the process of smashing hydrogen atoms together to form helium and releasing energy in the process. Dark stars work on a completely different principle. In the very early universe, the first clouds of hydrogen gas began collapsing under gravity in regions where dark matter was especially concentrated. As these gas clouds grew denser, they pulled even more dark matter inward through gravitational drag, creating pockets where dark matter particles were packed tightly enough to collide with each other frequently.
When two dark matter particles meet, they annihilate, converting their mass into energy (heat, light, and other particles). As the collapsing gas cloud grows denser, two things happen simultaneously: the dark matter concentration increases, and the gas becomes better at absorbing the energy released by those annihilations. At a critical density threshold, the heat pumped in by dark matter annihilation matches and then exceeds the cloud’s ability to cool itself. At that point, the outward pressure from dark matter heating can resist the inward pull of gravity, and the object stabilizes into something recognizable as a star, just one that runs on a completely different fuel source.
Size and Structure
Dark stars would have been radically different from any star that exists today. Because dark matter annihilation produces energy less efficiently per unit volume than nuclear fusion, a dark star needs to be far larger to remain stable. Theoretical models predict these objects could have swelled to extraordinary proportions, with masses ranging from roughly 10,000 to 10 million times the mass of our sun. Despite that tremendous mass, they would have had relatively cool, puffy surfaces compared to fusion-powered stars of similar brightness.
Their atmospheres would have been composed almost entirely of hydrogen and helium, the only elements that existed in significant quantities during the first few hundred million years after the Big Bang. This primitive composition is one of the features that distinguishes them from later generations of stars, which contain heavier elements forged in earlier stellar explosions.
Why They Matter for Black Holes
One of the biggest puzzles in astronomy is the existence of supermassive black holes, some weighing over a billion solar masses, at a time when the universe was less than a billion years old. Ordinary stellar evolution struggles to explain how black holes could have grown so large so quickly. Dark stars offer a potential solution.
Because dark matter annihilation prevents nuclear fusion from igniting, a dark star avoids the normal lifecycle that would eventually blow it apart in a supernova or limit its growth. Instead, it can keep accreting gas and growing for as long as its dark matter fuel supply holds out. Once that supply is exhausted, the star has no remaining energy source capable of supporting its own weight. A 2025 study showed that at masses in the range of tens of thousands to millions of solar masses, a general-relativistic instability causes the entire structure to collapse directly into a black hole. These black holes would then serve as seeds for the even larger supermassive black holes that telescopes have discovered at high redshift, neatly solving the timing problem.
Candidates Spotted by JWST
In 2023, a team led by Freese identified three objects observed by the James Webb Space Telescope’s JADES survey as the first dark star candidates: JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0. These objects exist at redshifts between roughly 11.6 and 13.2, meaning their light was emitted when the universe was only about 300 to 400 million years old. The team found that each object’s brightness and color could be explained by a supermassive dark star with a mass of 500,000 to one million solar masses.
The catch is that each of these objects is also consistent with being an early galaxy, a small collection of ordinary stars. Distinguishing between the two interpretations requires detailed spectral analysis, and researchers at the University of Texas at Austin have identified what they call a “smoking gun” signature: an absorption feature at a wavelength of 1,640 angstroms, caused by large amounts of singly ionized helium in a dark star’s atmosphere. If this feature shows up clearly in an object’s spectrum without the emission lines associated with galaxies (such as oxygen lines), it would strongly favor the dark star interpretation. For at least one candidate, observations from the ALMA radio telescope detected oxygen emission, which complicates the picture. If both the helium absorption and the oxygen emission are confirmed in the same object, it may not be an isolated dark star but could instead be a dark star embedded in a more chemically enriched environment.
What Dark Stars Need to Exist
The entire theory hinges on dark matter being made of a specific type of particle: a weakly interacting massive particle, or WIMP. WIMPs are one of several leading candidates for what dark matter actually is, but they haven’t been detected in laboratory experiments. If dark matter turns out to be something else entirely, such as ultralight particles or primordial black holes, then dark stars as described by this theory could not form.
Even assuming WIMPs exist, the dark matter density required is extreme. Modeling work has shown that ordinary stars sitting in typical dark matter environments, even near the center of a galaxy, cannot capture enough dark matter particles to significantly affect their energy output. The conditions that make dark stars possible existed only in the very early universe, when the first gas clouds collapsed inside the densest dark matter halos. This is why dark stars, if they ever existed, are a purely ancient phenomenon. No dark stars would be forming today.
An Open Question
Dark stars remain firmly in the territory of theoretical astrophysics. The JWST candidates are intriguing but ambiguous, and confirming or ruling out their existence will require sharper spectral data and possibly new observational tools. What makes the idea compelling is its explanatory power: a single mechanism that naturally produces supermassive objects in the early universe, which then collapse into the black hole seeds that conventional models struggle to account for. Whether that mechanism actually operated depends on questions about fundamental physics, particularly the nature of dark matter, that remain unanswered.