The “Little Red Dots 2026” workshop brought together an extraordinary concentration of expertise. Thirty-three invited speakers presented their latest results, nineteen researchers delivered rapid-fire flash talks, and in total 230 participants from institutions around the world joined the discussion. The event was explicitly dedicated to a single question: what, physically, are these compact red objects in the early Universe? That such a large community would converge on one class of sources reflects how profoundly the little red dots have unsettled the theoretical landscape. The meeting was chaired with the help of Jorryt Matthee and Roberta Tripodi, and the resulting report, published in Nature Astronomy by Dominik R. G. Schleicher of Sapienza Università di Roma, Andrés Escala of Universidad de Chile, Francesco Flammini Dotti of New York University Abu Dhabi, and Muhammad A. Latif of United Arab Emirates University, distills the state of a genuinely contested field.

The first little red dots were identified in early JWST surveys, with key discoveries reported by teams led by Jorryt Matthee and Jennie Greene in 2024 in the Astrophysical Journal. The sources stood out immediately for a combination of properties that seemed mutually incompatible. They are extremely compact, with sizes of only a few tens to a few hundred parsecs, yet they shine with luminosities that rival entire galaxies. Their spectral energy distributions peak in the rest-frame optical and are exceptionally red, a hallmark of either substantial dust attenuation or an intrinsically cool, dense source spectrum. Most strikingly, many of them exhibit broad emission lines, most notably broad H-alpha, a feature classically associated with gas moving at thousands of kilometers per second in the vicinity of an accreting supermassive black hole.

That spectroscopic signature propelled the little red dots to the center of the debate over black hole formation. If the broad lines trace a broad-line region, then each dot hosts an active galactic nucleus, and the inferred black hole masses typically fall between about one million and one hundred million solar masses, already assembled at redshifts of four to nine or beyond. Some of these black holes appear overmassive relative to their host galaxies by the standards of the local Universe, echoing other JWST discoveries of surprisingly massive early black holes. For theorists studying direct-collapse black holes and heavy black hole seeds, the population is a potential treasure trove, and work by researchers such as Muhammad Latif and colleagues has explored how the conditions of the pristine early Universe could plausibly produce such massive seeds.

Yet the active-galactic-nucleus interpretation is not without problems, and the workshop gave ample space to the tensions. Little red dots largely lack the X-ray emission that typically accompanies accretion onto black holes, a puzzle highlighted in studies by Tonima Ananna, Ákos Bogdán and collaborators. Many also lack the variability expected of standard accretion disks and show no strong evidence for the outflows or ionization signatures common in classical quasars. Robert Maiolino and collaborators, and independently Igone Juodžbalis and colleagues in a 2026 Nature paper, have argued for scenarios in which the accretion flow is dense and optically thick, potentially super-Eddington, burying the X-ray emitting inner region from view. Vasily Rusakov and collaborators, also in Nature, presented evidence bearing directly on the central engine question, and the accumulating dataset has forced modelers to consider accretion geometries very different from the thin disks of nearby quasars.

A rival family of models makes the debate even sharper: perhaps the little red dots are not dominated by black holes at all. Several groups have proposed that the compact red light comes from extraordinarily dense and massive stellar systems, sometimes described as nuclear star clusters pushed to physical extremes. Work by Lucio Mayer, Pedro Capelo, Lixin Zwick and Tiziana Di Matteo explored how compact massive structures could form, and Michele Brazzini and colleagues examined whether such stellar populations could reproduce the observed colors. More exotic proposals discussed at the meeting include the so-called supermassive star or “black star” scenarios, in which enormous, nearly monolithic stellar objects embed a central black hole and produce broad, dense-gas spectral features without a conventional quasar disk. The reported lack of variability and the peculiar line shapes have kept these stellar hypotheses alive, because a single compact stellar population could, in principle, mimic some quasar-like signatures while avoiding their drawbacks.

The community is now converging on a diagnostic strategy rather than a single verdict. Variability studies, deep spectroscopy of the broad lines, analysis of the balmer breaks seen in some of the brightest dots, and searches for X-ray and radio counterparts are being deployed to separate accretion-dominated from star-dominated scenarios. Josephine Baggen and colleagues examined the stellar mass and size constraints, finding that some dots imply stellar population properties that push against physical limits, while other analyses, including work by Ruochen Lin and collaborators, focus on the demographics and duty cycles of the population. Fabian Loiacono’s team and Connor Williams’ group have both contributed new observational constraints reported as preprints in 2026, illustrating how quickly the observational foundation is growing. The Emerging Populations initiative associated with the CEERS and related survey programs continues to expand the sample, providing the statistical power needed to test whether the dots form a homogeneous class or several physically distinct populations.

What is increasingly clear is that the answer matters far beyond the classification of a curious class of sources. If the little red dots are accreting supermassive black holes, they constrain the earliest chapters of black hole growth and may point to heavy seeds formed through direct collapse, with implications for the gravitational wave backgrounds targeted by pulsar timing arrays and for the buildup of the black holes later observed by LISA and electromagnetic surveys. If they are dense stellar systems, they probe star formation under conditions of extreme density that the local Universe simply cannot reproduce, testing the physics of star formation at gas surface densities orders of magnitude above those in today’s galaxies. And if the truth is mixed, the little red dots may record a brief transitional phase in which nuclear star clusters and nascent black holes coexist, evolve, and feed one another during the first billion years of cosmic history.

The Little Red Dots 2026 meeting made plain that this field is moving at a pace rarely seen in astronomy, with new JWST programs, deeper spectroscopy and theoretical simulations arriving almost monthly. As the workshop report by Schleicher and colleagues emphasizes, the community’s goal for the coming cycle is to convert a bewildering ensemble of colors, line widths and luminosities into a coherent physical picture of compact red objects in the early Universe. Whether these enigmatic sources turn out to be the cradles of the first supermassive black holes, the most extreme star clusters ever assembled, or something in between, they have already reshaped how astronomers think about the first billion years, and the next round of observations promises to bring one of the most exciting debates in astrophysics closer to resolution.

Subject of Research: The physical nature of little red dots, compact red objects discovered by JWST in the early Universe

Article Title: Little Red Dots 2026

Article References: Schleicher, D. R. G., Escala, A., Flammini Dotti, F., & Latif, M. A. (2026). Little Red Dots 2026. Nature Astronomy. https://doi.org/10.1038/s41550-026-02967-7

Image Credits: AI Generated

DOI: 10.1038/s41550-026-02967-7

Keywords: little red dots, JWST, early Universe, supermassive black holes, active galactic nuclei, high redshift galaxies, broad emission lines, compact sources, super-Eddington accretion, black hole seeds, nuclear star clusters, cosmic dawn

The intellectual foundations of the subject were laid in the 1960s and 1970s. Salpeter and, independently, Zeldovich and Novikov recognized that radiation pressure from an accreting nucleus could push surrounding gas outward, limiting growth and luminosity. The balance between outward radiation force and inward gravity defines the Eddington luminosity, which scales linearly with mass. In 1973, Shakura and Sunyaev supplied the master framework that still governs the field: at high accretion rates, radiation pressure inflates the geometrically thin disc until, beyond a characteristic radius, the disc half-thickness becomes comparable to its radius. Inside this so-called spherisation radius, the disc can no longer hold itself together, and matter is blown off its surface in a powerful, radiation-driven wind. The self-regulating mechanism proposed by Shakura and Sunyaev, in which the outflow carries away excess mass while photons are effectively trapped in the optically thick inflow, remains the backbone of every modern super-critical accretion model.

Two further theoretical innovations shaped the modern understanding. First, Begelman showed in 1979 that in optically thick flows, photons become trapped and are advected inward with the gas, so that much of the accretion energy is swallowed by the black hole rather than radiated. Second, Abramowicz, Czerny, Lasota and colleagues developed the slim disc model in 1988, a solution in which radial advection of heat is an unavoidable cooling channel and the flow remains thermally stable even far above the Eddington rate. The signature prediction is subtle but profound: because of photon trapping and wind-driven mass loss, the bolometric luminosity grows only logarithmically with accretion rate, roughly as the Eddington luminosity multiplied by one plus the natural logarithm of the dimensionless accretion rate. A black hole fed a thousand times its Eddington supply therefore shines only a few times brighter than the classical limit, while the rest of the inflowing mass is flung back into space through the wind.

The review also traces the stranger corners of the theory, including the famous Polish doughnut, an elegant three-dimensional analytic solution for very high mass accretion rates in which a thick, low-viscosity, optically opaque torus forms around the hole. Such tori concentrate their emission into a narrow polar funnel and can geometrically collimate radiation and jets, an idea originally proposed by Lynden-Bell in 1978 to explain both active galactic nuclei and the enigmatic Galactic source SS 433. Later work showed that strong advective cooling thins and dims these doughnuts considerably, and the modern consensus favors a hybrid picture: a radiation-pressure-dominated, advective inner disc sheathed in an optically thick wind, with mass loss concentrated near the spherisation radius. For magnetized neutron stars, the auto-regulation picture acquires an extra layer, since the magnetosphere truncates the inner disc, and the maximum accretion rate onto the stellar surface depends on the magnetic dipole moment as well as the Eddington luminosity, scaling with the dipole moment to the four-ninths power.

The observational revolution arrived with the recognition that ULXs in nearby galaxies are genuine super-Eddington accretors rather than hidden intermediate-mass black holes. The decisive twist came when pulsations were discovered in several ULXs, proving that at least some of these extreme sources are powered by neutron stars with solid surfaces and strong magnetic fields. Accommodating such sources demanded new physics: magnetospheric truncation of the disc, columnar accretion along field lines onto the magnetic poles, and a reduced effective scattering cross-section in strong magnetic fields that allows the star to radiate far above the canonical Eddington limit. Accretion columns form above the surface, shocks settle within them, and radiation escapes largely through the sides of the column in a fan-beamed pattern rather than as pencil beams, consistent with the moderate pulse fractions observed in ultraluminous X-ray pulsars.

Numerical simulation has transformed the field from a collection of one-dimensional analytic models into a genuinely multi-dimensional science. Pioneering two-dimensional radiation-hydrodynamic simulations by Ohsuga and colleagues in 2005 demonstrated self-consistently how a geometrically and optically thick, radiation-pressure-dominated disc forms and launches outflows without assuming any disc configuration in advance. Photons are visibly trapped and dragged into the hole with the gas, while radiatively driven winds emerge from the disc surface with mildly collimated radiation along the rotation axis. Subsequent radiation-magnetohydrodynamic simulations removed the artificial alpha-viscosity prescription and incorporated magnetic turbulence directly, revealing radiatively accelerated, magnetically collimated jets. General relativistic versions of these calculations showed that black hole spin dramatically raises the energy conversion efficiency, from roughly five percent for a non-spinning hole to about thirty-three percent for a spin parameter of 0.9, and up to 140 percent in the magnetically arrested disc regime, where the Blandford-Znajek mechanism extracts rotational energy to power powerful jets. Simulations in this state even suggest that super-Eddington discs in a magnetically arrested configuration can spin their black holes down over time.

The simulations also predict structural features that observations can test. Disk winds fragment into clumpy gas clouds through Rayleigh-Taylor instabilities, and such clumpy, structured winds may explain both the X-ray variability of ULXs and the multiple absorption lines recently detected by the XRISM satellite in ultrafast outflows from a distant quasar. Large-domain simulations show that outflows are launched across the entire region within the photon trapping radius, with the highest mass-loss rates occurring not closest to the black hole but somewhat farther out, and with failed outflows that stall and fall back near the trapping radius. The outflow mechanical power inferred for ULXs, in the range of 10^39 to 10^41 erg per second, is comfortably consistent with the energetics of the vast bubble nebulae inflated around some of these sources. Even the puzzling X-ray weakness of the so-called Little Red Dots in the early Universe has been explained using simulation-based spectra of mildly super-Eddington, slowly spinning black holes viewed at moderate inclinations.

Observationally, the broadband X-ray spectra of ULXs now split naturally into components that map onto the theory: a soft, outflow-modified disc component peaking near the spherisation radius that violates the standard luminosity-temperature relation expected of thin discs, and a harder component that is comparatively insensitive to accretion rate. Because the thick wind obscures the innermost regions from most viewing angles, the apparent luminosity of a super-critical source depends strongly on inclination, giving rise to a geometric unification model in which face-on systems appear ultraluminous while edge-on ones look comparatively modest or even supersoft. Resonant absorption lines resolved in high-resolution X-ray spectra have confirmed powerful winds across the ULX population, and related ultrafast outflows have now been detected in tidal disruption events and quasi-periodic eruption sources, suggesting a common physics spanning eight orders of magnitude in accretor mass. Polarization measurements with IXPE have even revealed the predicted funnel geometry in the Galactic source Cygnus X-3, while NuSTAR phase-resolved spectroscopy showed that SS 433, viewed more face-on, would radiate at super-Eddington levels.

Substantial puzzles remain. Whether the inner flow is magnetically arrested or not, how much mass actually reaches the compact object, and how advection competes with wind-driven mass loss all remain contested, and different feeding prescriptions in simulations yield divergent answers. Timing features such as quasi-periodic oscillations in ULXs, possibly produced by Lense-Thirring precession of the tilted super-Eddington disc, still lack definitive confirmation, and recent work proposes that quasi-periodic eruptions in galactic nuclei may be the high-mass cousins of the same precessing flows. The path forward, the review argues, lies in the tight coupling of longer-duration general relativistic radiation-magnetohydrodynamic simulations running on modern GPU-based codes with the next generation of instruments: XRISM’s high-resolution spectroscopy of structured winds, the Vera Rubin Observatory’s harvest of tidal disruption events, NewAthena’s sensitivity to faint pulsating neutron star ULXs, and the SKA’s ability to chart the jets. Together these efforts promise to convert super-Eddington accretion from a beautiful theoretical curiosity into a precision tool for understanding how black holes grow, how neutron stars survive impossible feeding rates, and how radiation-hungry monsters across the cosmos regulate themselves.

Subject of Research: Super-Eddington accretion onto stellar-mass black holes and neutron stars

Article Title: Super-Critical Accretion onto Stellar Mass Black Holes and Neutron Stars: A Short Review

Article References: Middleton, M., Lipunova, G., Ohsuga, K., & Abramowicz, M. (2026). Super-Critical Accretion onto Stellar Mass Black Holes and Neutron Stars: A Short Review. Space Science Reviews, 222(6), Article 71. https://doi.org/10.1007/s11214-026-01318-2

Image Credits: AI Generated

DOI: 10.1007/s11214-026-01318-2

Keywords: super-Eddington accretion, Eddington limit, ultraluminous X-ray sources, black holes, neutron stars, accretion discs, disk winds, photon trapping, slim disc model, GR-RMHD simulations, ULX pulsars, Space Science Reviews