The nature of 'little red dots' (LRDs) based on JWST data is a profound mystery. The quasi-star model (shells around black holes born from the collapse of supermassive stars) looks promising, but the classic scenario requires rare conditions: a strong Lyman-Werner background to suppress molecular cooling, a high accretion rate for entropy stratification, and rotation to prevent collapse down to ~10⁶ M⊙. It has been shown that supermassive dark stars, fueled by dark matter annihilation, naturally bypass these constraints and form quasi-stars. The resulting black holes immediately gain ≳10% of the progenitor's mass, and the envelope expands, cooling to the opacity limit (Teff~3000–6000 K), characteristic of zero metallicity. Such cold, unresolved photospheres reproduce the spectra and morphology of many LRDs.
The mystery of ‘little red dots’ (LRDs) challenges our understanding of the formation of the first objects in the expanding Universe. These compact, ultraluminous sources, observed at redshifts z≳7, defy standard stellar and active nucleus models. If LRDs are indeed quasi-stars — envelopes around supermassive black holes — then their formation mechanism must operate under conditions thought to require extreme fine-tuning. Understanding an alternative channel involving dark matter, whose existence on galactic scales is confirmed by Vera Rubin's observations, could not only explain the data but also shed light on the nature of dark matter and the growth of the first black holes in massive galaxies.
The authors used supermassive dark star models generated by the stellar evolution code MESA. A benchmark non-rotating SMDS powered by annihilation of WIMPs with a mass of 100 GeV was adopted. The onset of general-relativistic instability was identified using the Chandrasekhar criterion for radiation-dominated stars: when the pressure-averaged adiabatic index ⟨Γ₁⟩ drops below the critical value ≃4/3 + C⋅GM/(Rc²). Then, the mass of the instantly formed black hole, the binding energy of the leftover envelope, and the feasibility of its subsequent expansion to quasi-star–like sizes were estimated.
It turns out that the SMDS reaches the relativistic instability limit at a mass of about 2.6×10⁶ M⊙ and a radius of ~1.7×10⁴ R⊙. Its effective temperature was ~2.6×10⁴ K, and its luminosity was nearly Eddington (~10¹¹ L⊙). Unlike classical supermassive stars, where only a small core collapses, the SMDS structure implies the formation of a massive initial black hole: the authors adopt a fiducial M_BH,0 ≈ 10⁶ M⊙, almost 40% of the star’s mass. The remaining envelope (~1.6×10⁶ M⊙) has a binding energy of about 7×10⁵⁶ erg. The energy released during the collapse, combined with subsequent accretion feedback, is sufficient to inflate the envelope by a factor of ~25 and turn it into a cold quasi-star with a photosphere at a radius of ~4.2×10⁵ R⊙. At an effective temperature of 3000–6000 K, set by the opacity of a zero-metallicity medium, such a quasi-star would appear as a compact, very red object with a bolometric luminosity of ~10¹¹ L⊙ — exactly like the observed LRDs. Moreover, the huge surface density (~10⁵ g/cm²) and corresponding hydrogen column density (~10²⁸ cm⁻²) ensure that the central black hole’s radiation is efficiently reprocessed and hidden from direct view, as confirmed by spectroscopic data.
The proposed scenario elegantly solves several problems: it does not require a strong Lyman–Werner background to suppress H₂ cooling, extreme accretion rates, or finely tuned rotation to prevent premature collapse. This widens the range of environments where supermassive black hole seeds can form in early galaxies. Moreover, if dark matter indeed acts as ‘fuel’ for the first stars, this could indirectly hint at the nature of dark matter particles and their annihilation cross-section.
Future research should include full-scale hydrodynamic simulations of SMDS collapse within general relativity to accurately determine the dynamics of black hole formation and the envelope’s response. It is also crucial to perform detailed radiative transfer in the atmospheres of such ‘dark quasi-stars’ for direct comparison of synthetic spectra with data from JWST and future telescopes. Such objects might even be detectable in the gravitational-wave band when the resulting black holes merge.
The findings will impact early-Universe cosmology, the theory of supermassive black hole formation, and JWST observational astronomy. They also stimulate the search for dark matter signatures in the spectra of the first objects.
Analysis of pulsational stability of SMDSs and collapse modeling with relativistic hydrodynamics codes is planned. Detailed comparison with spectra of LRDs obtained by JWST will also be conducted.
This work is directly linked to the mystery of the origin of supermassive black holes in the early Universe, the nature of dark matter, and the interpretation of unexpected JWST discoveries that challenge the standard cosmological model.
🎯 Supermassive dark stars, if they exist, could have radii comparable to the orbit of Jupiter and shine solely from dark matter particle annihilation rather than nuclear fusion. If we could see such a star through a telescope, it would look like a giant, cold ball slowly devouring space itself.