Front. Astron. Space Sci. Frontiers in Astronomy and Space Sciences Front. Astron. Space Sci. 2296-987X Frontiers Media S.A. 1779045 10.3389/fspas.2026.1779045 Mini Review Little red dots: the assembly of early supermassive black holes in the JWST Era Vaida and Farber 10.3389/fspas.2026.1779045 Vaida David D. 1 * Writing – review and editing Writing – original draft Farber Ryan Jeffrey 2 Writing – review and editing Independent Researcher, Cherry Hill, NJ, United States Department of Physics, Purdue University Fort Wayne, Fort Wayne, IN, United States Correspondence: David D. Vaida, ddvaida28@gmail.com 24 02 2026 2026 13 1779045 31 12 2025 31 01 2026 05 02 2026 Copyright © 2026 Vaida and Farber. 2026 Vaida and Farber https://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

Since the launch of the James Webb Space Telescope (JWST) in late 2021, our understanding of high-redshift objects has faced several upheavals. JWST has discovered much more massive galaxies and supermassive black holes (SMBH) than cosmological models had expected. Furthermore, JWST observations have revealed an entirely novel population of high-redshift objects. Characterized by a dominant red rest-frame optical continuum and point-like morphology, these “little red dots” (LRD) have set off a flurry of observational and theoretical follow-up. The current identity of LRD is highly debated, yet falling into two main scenarios: active galactic nuclei (i.e., SMBH) or compact star-forming regions. If star-forming, LRD would represent the highest stellar densities ever observed. If SMBH, their high Eddington fractions, and already high masses, help elucidate the growth of the most massive SMBH found by JWST in the early Universe ( z ≳ 4 ) . In this mini-review, we present the observational evidence accumulated to date, including sub-millimeter probes of LRD dust masses, constraints on radio and X-ray emission from stacking, and rest-frame ultraviolet and optical measurements provided by JWST. Furthermore, we highlight how identifying additional LRD that are truly primarily SMBH-driven may help to shed light on the formation of ‘overly massive’ SMBH discovered by JWST within the first billion years since the Big Bang.

 AGN direct collapse black holes JWST little red dots primordial black holes super-Eddington accretion supermassive black holes supermassive stars The author(s) declared that financial support was not received for this work and/or its publication. section-at-acceptance Extragalactic Astronomy Introduction

Since the launch of the James Webb Space Telescope (JWST; Gardner et al., 2023; McElwain et al., 2023) ∼ 4 years ago, JWST has discovered an increasing population of supermassive black holes (SMBH; e.g., Castellano et al. 2022; Natarajan et al. 2023) that challenge the current paradigm of black hole formation and growth (Jacak, 2025), and see the recent review by Harikane (2025). Specifically, JWST-discovered SMBH are far more massive than expected to be present at such high redshifts, with ∼ 1 0 9   M ⊙ black holes already in place within the first billion years after the Big Bang (Labbé et al., 2023), suggesting much more rapid formation than would be possible for Pop III stellar remnants accreting at the Eddington limit (Kiyuna, 2026 and see the ∼ recent reviews Inayoshi et al., 2020; Volonteri et al., 2021; Jeon et al., 2025a).

Instead, these “overly” massive SMBH may have formed through Eddington-limited accretion from heavy seeds, such as direct collapse black holes from atomic cooling halos and supermassive stars (Kiyuna et al., 2024; Lu et al., 2024; Jeon et al., 2025b), or primordial black holes (Delos et al., 2024; Riotto and Silk, 2025; Carr and Green, 2025). Alternatively, these SMBH may have formed through hierarchical merging of light seed black holes in active galactic nucleus (AGN) disks (Vaccaro et al., 2024), in dense nuclear or globular star clusters (Kritos et al., 2025; Lahén et al., 2025), or had their growth rates boosted beyond the Bondi rate (and Eddington limit) via fuzzy dark matter soliton cores (Chiu et al., 2025).

Clearly, much uncertainty exists regarding precisely how SMBH grew so rapidly in the early Universe. Perhaps the most direct way to uncover the physical mechanisms responsible is to identify a population of lower-luminosity accreting black holes at high redshift, whose more modest accretion rates provide constraints on both seed masses and early growth histories (Akins et al., 2025c). Such intermediate-mass systems offer a critical bridge between initial seed formation and the most massive SMBH observed by JWST.

Possibly constituting such an intermediate population in an active state, little red dots (LRD) describe a typically high-redshift population with compact morphology, broad ∼ 1000   k m   s − 1 H α line widths (Kocevski et al., 2024; Zhang et al., 2025), and simultaneously blue ultraviolet (UV) continua yet red rest-frame optical colors (Setton et al., 2024; Hviding et al., 2025). Originally, LRD were detected at redshifts 4.2 < z < 5.5 (Matthee et al., 2024); however, subsequent JWST observations have uncovered a larger population extending from 3 < z < 10 (Labbe et al., 2024; Graham et al., 2025). In addition to their characterization by JWST imaging and spectroscopy, LRD have been investigated by increasingly deep multiwavelength campaigns stretching from radio to X-ray bands.

In this mini-review, we highlight the findings of the most recent LRD observations across the electromagnetic spectrum with a focus on identifying the physical origins of LRD. In Section 2, we contextualize the discovery of LRD with respect to the first few JWST surveys performed. Subsequently, in Section 3, we discuss additional multi-wavelength studies that complete the characterization of LRD. Synthesizing the observations detailed in prior sections, in Section 4, we discuss the physical interpretations of LRD that claim to explain their observed properties. Finally, we zoom-out and discuss the state of the field of LRD origins more broadly, along with the future directions that can more conclusively end the controversy in Section 5. Understanding these mechanisms is crucial for accurately interpreting high-redshift observations and for uncovering how the first SMBH originated.

 LRD discovery through the lens of JWST surveys

Some of the first images from JWST, utilizing the Near Infrared Camera (NIRCam; Rieke et al., 2023) through the Cosmic Evolution Early Release Science program (CEERS; Finkelstein et al., 2023), were found to contain very red galaxies (e.g., Endsley et al., 2023; Labbé et al., 2023; Onoue et al., 2023). These objects were initially interpreted as massive high-redshift galaxies whose inferred stellar masses appeared inconsistent with expectations from the standard cosmological model Λ Cold Dark Matter (CDM; Boylan-Kolchin 2023; Ferrara et al. 2023; Lovell et al. 2023).

Subsequent analysis incorporating constraints from the Mid-Infrared Instrument (MIRI; Argyriou et al., 2023), together with spectroscopy from the Near-Infrared Spectrograph (NIRSpec; Bagnasco et al., 2007), revised these mass estimates downward relative to the original photometry-only inferences. At the same time, these observations revealed very broad Balmer emission lines and a V-shaped spectral energy distribution (SED), characterized by blue rest-frame ultraviolet emission combined with red rest-frame optical colors (Kocevski et al., 2023; Barro et al., 2024).

Although a small fraction of these red objects were later found to be foreground brown dwarfs, a larger sample of low-luminosity red objects at high-redshift with a characteristic V-shaped SED, point-like morphology, and broad Balmer lines (Furtak et al., 2023; Greene et al., 2024; Labbe et al., 2024) were discovered through the Ultradeep NIRSpec and NIRCam Observations before the Epoch of Reionization (UNCOVER; Bezanson et al., 2024)) program. Combining deep NIRCam photometric and wide-field slitless spectroscopy (WFSS; grism) observations from the EIGER (Kashino et al., 2023) and FRESCO (Oesch et al., 2023) surveys, Matthee et al. (2024) coined the term ‘little red dots’ to explain the surprisingly abundant population: about 1% of galaxies at redshift z > 5 were found to host LRD, while the number density 1 0 − 5 cMpc − 3 (co-moving cubic Mega-parsec) is 10 times larger than expected by extrapolating the UV luminosity function.

Following up on the primarily photometric surveys that incidentally contained little red dots, the Red Unknowns: Bright Infrared Extragalactic Survey (RUBIES; De Graaff et al., 2025), was designed to specifically investigate LRD through a homogeneous spectroscopic survey. Utilizing NIRSpec and covering cosmic noon ( z ∼ 2) and earlier, RUBIES has revealed that LRD show a spectroscopic link between three defining characteristics: broad Balmer lines, a rest-frame optical point source, and a V-shaped continuum, across 1500 galaxies studied (Hviding et al., 2025).

The characteristic bimodal spectral energy distribution was further established across a large spectroscopic sample as one of the defining characteristics of LRD (Hviding et al., 2025). In Figure 1, we present the primary diagnostic panels adapted from Figures 6–8 of Hviding et al. (2025), illustrating three complementary RUBIES results. First, the β UV – β opt plane shows that compact red sources occupy a tight locus that is clearly distinct from the overall RUBIES galaxy population. Second, an Euler diagram quantifies the strong overlap among the three main LRD selection criteria: broad Balmer lines, a dominant rest-frame optical point source, and a V-shaped continuum. Third, demographic trends linking redshift to the JWST F356W/F444W flux ratio, as well as the UV absolute magnitude M UV to L H α , indicate that LRDs are systematically UV-faint at fixed L H α yet dominate among the most extreme H α emitters. Taken together, these diagnostics tie the characteristic blue-UV/red-optical SED to unresolved central structures and broad Balmer emission, a signature consistent with compact, partially obscured accretion.

Adapted from Figures 6–8 of Hviding et al. (2025), illustrating the diagnostic framework used by the RUBIES survey to define the Little Red Dot (LRD) population. (a) The β UV – β opt maps show where sources with broad Balmer lines, unresolved rest-frame optical point sources, and V-shaped continua lie relative to the full sample of galaxies with z spec > 3.1 . (b) An Euler diagram and accompanying bar plot demonstrate that the combination of a compact point source and a V-shaped continuum implies an ∼ 80% probability of hosting broad Balmer emission. Heatmaps showing the photometric flux in two JWST filters for high- and low-redshift sources (threshold z = 5 ) as a function of spectroscopic redshift, and the spectroscopically derived ultraviolet absolute magnitude versus H α luminosity. (c) These diagnostics show that Little Red Dots are systematically UV-faint at fixed L H α and dominate the most H α -luminous objects at fixed M UV ( F 356 W for z spec ≤ 5 ; F 444 W for z spec > 5 ).

Scientific figure with three panels: (a) shows scatterplots comparing spectral indices for different subsets; colored points represent sample groups, density maps are in grayscale, and a highlighted sample uses red hexagons. (b) shows a Venn diagram with overlapping colored circles for Broad Balmer, Rest-Opt. Point Source, and V-Shape categories, plus a bar chart dividing object classifications by confidence level. (c) contains two density scatterplots, one plotting observed magnitude versus redshift and another plotting UV magnitude versus H-alpha luminosity, each overlaying red hexagons and displaying count histograms across the top. Observational constraints on LRD

Studying the rest-frame UV of LRD, detections of the high-ionization coronal line [FeX] strongly suggest an AGN nature (Kocevski et al., 2023; Furtak et al., 2024). On the other hand, non-detections of HeII emission lines in the far UV (FUV) and MgII are more consistent with photoionization by massive stars (Akins et al., 2025a). Additionally, a Balmer break, observed for many LRD, typically suggests an aged stellar population, though it is not universal (Akins et al., 2025a). On the other hand, detections of strong C IV, marginal He II λ 4686 line (in the rest-frame optical) and [Fe x], together with broad H α all combined strongly support an AGN interpretation (Inayoshi and Maiolino, 2025).

As early as 2024, it was reasoned that (most) LRD dust masses must be quite limited < 1 0 4 − 5   M ⊙ due to their compact sizes yet relatively low mass available for attenuation (Casey et al., 2024). Indeed, deep NOEMA observations of z > 7 LRD (Xiao et al., 2025) as well as multi-band Atacama Large Millimeter/Submillimeter Array (ALMA; Wootten and Thompson, 2009) observations of a couple of the brightest LRD known resulted in stringent non-detections (Setton et al., 2025). Observations of a larger sample ( ∼ 60 ) LRD with ALMA in the 1.3 mm continuum band similarly resulted in no detections, even with stacking, suggesting LRD either have modest dust reservoirs ( A v ∼ 2 − 4 ) or otherwise very dense gas 1 0 9   c m − 3 causes the obscuration. The deficit of dust in LRD extends to a broader range of wavelengths in the far-IR, sub-mm and radio: LRD observations in the rest-frame IR in Spitzer/MIPS 24 μ m, JCMT/SCUBA-2 850 μ m, and ALMA 1.2 and 2.0 mm (Bao et al., 2025). Additionally, the lack of radio counterparts in MeerKAT/VLA 1.3 and 3.0 GHz observations (Bao et al., 2025) suggests a lack of the synchrotron emission often associated with either AGN jets or the intense star formation that typically accompanies large dust reservoirs.

Consistent with non-detections at redder wavelengths, Brooks et al. (2025) investigated the dust attenuation of Balmer narrow-line emission and broad-line signatures in 29 z > 3.5 AGN selected from JWST surveys (CEERS, JADES, and RUBIES). Brooks et al. (2025) find that the blue UV component is consistent with unattenuated star formation on galactic scales, whereas the red optical component is consistent with a dust-obscured AGN. Specifically, they place a lower limit on the dust attenuation A v > 3.6 for the AGN component due to the non-detection ( < 3 σ ) of the broad H β line even after stacking 25 of their sources.

The scope of multi-wavelength constraints has expanded as increasingly larger populations of LRD are analyzed. Studying 434 LRD in the JWST COSMOS-Web survey, Akins et al. (2025c) find no detections, even when stacking, in X-ray, mid-IR, far-IR/submillimeter, and radio bands. These findings align with previous targeted studies and representative samples that found LRD are not detected, or quite weakly emitting, in X-ray (Ananna et al., 2024; Yue et al., 2024; Maiolino et al., 2025) and in radio (Mazzolari et al., 2024; Perger et al., 2025; Gloudemans et al., 2025). Similarly, the faint end X-ray luminosity function at z > 4 suggests a reservoir of accretors with weak coronal efficiency, which agrees with the X-ray quiet nature of many LRD (Barlow-Hall and Aird, 2025).

 Interpretations of LRD: stellar vs. AGN scenarios

We next consider how LRD spectral properties arise and why AGN and stellar interpretations can both appear. Forward modeling shows that an AGN continuum with rest-frame absorption by dense dust-poor gas can generate a strong Balmer break and broad Balmer lines, a combination that matches a spectroscopic LRD with tentative variability of the H α equivalent width, detected at a significance of 2.6 σ (D’Eugenio et al., 2026).

In particular, the inclusion of mid-IR and redder data (from MIRI & ALMA) has led to mixed results. While the red optical and near-IR data can be fit by an obscured inner accretion disk with scattered AGN light (Lambrides et al., 2024; Pacucci and Narayan, 2024; Madau, 2025), stellar-dominated (even starburst) models provide improved fits compared to the AGN scenario (Pérez-González et al., 2024; Carranza-Escudero et al., 2025). Moreover, the concerns that a stellar nature of LRD is inconsistent with the maximal brightness surface density in the local universe (Hopkins et al., 2010; Akins et al., 2025c), is alleviated due to MIRI and ALMA observations decreasing the requisite stellar mass (Williams et al., 2024). On the other hand, recent analysis of LRD from the JWST Advanced Deep Extragalactic Survey (JADES; Eisenstein et al., 2023) with NIRCam and MIRI photometry suggest one LRD with a 2% AGN contribution to the luminosity, one completely star-forming, and the rest with 20%–70% contributions from AGN (Durodola et al., 2025). Similarly, recent analysis of MIRI data increases the spectral fit for stellar components, reducing the number of AGN-only solutions without eliminating AGN altogether (Furtak et al., 2025).

To explain the quiescence of radio, X-ray, and far-IR/sub-mm emission, modeling work has extended beyond the standard models of AGN. Quasi star or black hole envelope models predict compact very red sources with strong Balmer features during specific evolutionary phases of the quasi star or black hole envelope that overlap LRD selections, suggesting some LRD may represent heavy seeds of SMBH in formation (Begelman and Dexter, 2025; Durodola et al., 2025). Black hole envelopes embedded in dense gas can also reproduce red continua and strong lines in a way that mimics faint AGN (Kido et al., 2025; Naidu et al., 2025). On the other hand, simulations of collapsing clusters predict enhanced tidal disruption activity and luminous transients that can generate broad lines and variable continua in compact systems, offering another channel that suggests a non-standard origin of LRD with rapid black hole growth in cluster cores (Bellovary, 2025). Dusty inflow models explain very red rest-optical colors and broad absorption and predict that mid-IR observations should be constraining (Li et al., 2025). Simulations of high redshift environments indicate that compact AGN can arise in gas rich protoclusters where repeated fueling and multiphase outflows sculpt line profiles and continuum shape (Kannan et al., 2025). Observations of multiphase outflows around z ∼ 5 quasars show that such winds can be common and energetic, which supports the idea that some LRD reflect wind-bearing accretion states rather than aged stellar populations (Brazzini et al., 2025). These models collectively predict that modest changes in geometry, column density, and recent fueling history can toggle an object between apparently AGN-like and stellar-like diagnostics, which explains why LRD form a mixed class.

Considering a background LRD at redshift 7 from UNCOVER with multiple images due to gravitational strong lensing of the foreground cluster Abell 2744, Furtak et al. (2025) investigated photometric and spectroscopic time variability, leveraging lensing time delays 1 of 22 years (rest-frame ∼ 3 yr) between the images. Finding significant variability in H α and H β lines, Furtak et al. (2023) confirmed the AGN nature of this LRD. We present Figure 1 from Furtak et al. (2025) as Figure 2. Clearly, the H α and H β line fluxes have evolved significantly from epoch 7 (marked in dark blue) to epoch 8 (marked in light blue). This constitutes strong AGN evidence for several reasons. First, the Balmer lines are very broad (FWHM a few 1 0 3  km s-1), which requires the high velocities of gas near a black hole and cannot be produced by normal star-forming H II regions. The line fluxes and profiles vary on rest-frame ∼ year timescales, the expected behavior of a compact broad-line region responding to a changing ionizing source. Since the spectra are normalized and the multiple images are separated by known lensing delays, the differences cannot be due to calibration or lensing and must be intrinsic. Photometric non-variability does not contradict this result, since AGN continuum variability is stochastic and can be modest over the sampled interval.

Figure credit: Lukas Furtak and Adi Zitrin, as adapted from Furtak et al. (2025), their Figure 1. This figure provides direct spectroscopic evidence for accretion in the little red dot A2744-QSO1. JWST/NIRSpec-prism observations of the multiply imaged (due to gravitational strong lensing) source A2744-QSO1 at multiple epochs capture the full Balmer region and reveal broad H α and H β and their variability. After placing the spectra on a common reference and scaling line profiles by the local continua, the broad shapes persist while only modest equivalent-width changes remain, which is consistent with AGN variability. These measurements show that some LRD host broad-line regions even when continuum variability is weak, supporting an interpretation in which at least part of the LRD population traces active black hole growth (Furtak et al., 2025).

Scientific data visualization showing three main panels: a large spectral line graph with four color-coded lines representing different images and epochs, a horizontal spectrum image below it, and two smaller line graphs on the right displaying H-beta and H-alpha emission lines with shaded error regions. Discussion and conclusion

Despite recent progress, many caveats surround the work performed to-date attempting to identify the nature of LRD. Many LRD are X-ray and radio quiet even in stacks, which could be consistent with heavy obscuration and low coronal efficiency. This low efficiency in the AGN’s X-ray corona is expected from super-Eddington accretion models where thick disks suppress high-energy emission (Secunda et al., 2025; Inayoshi and Maiolino, 2025); on the other hand, stellar templates fit a large fraction of LRD with mid-IR data included (Hainline et al., 2025). Radio and X-ray constraints specific to compact high redshift sources show that non detections do not rule out accretion for the luminosities expected from specific accretion flows (thick trapping dominated flows), which raises the need for deeper follow-up observations (Latif et al., 2025). Deeper observations in radio bands may finally uncover detections if even a minority of LRD host jets or compact cores. These upcoming observations will provide a near-term observational test of the mixed population picture (Latif and Whalen, 2025).

Completeness studies for obscured narrow-line AGN show that color cuts and emission line thresholds can miss faint or partially obscured accretors, implying that some LRD-like systems may be absent from current AGN catalogs and that selection bias can skew interpretations (Bouwens et al., 2025; Scholtz et al., 2025).

Ultimately, LRDs likely comprise both genuine rapidly growing black holes and compact star-forming systems. Resolving their roles in early black hole demographics will require deeper mid-IR coverage, higher signal-to-noise spectroscopy that targets both Balmer and high-ionization UV lines, and radio and X-ray follow-up matched to the efficiencies expected for thick discs rather than thin ones (Akins et al., 2025b).

In particular, measuring time variability in photometric flux and spectral line profiles would provide ‘smoking-gun’ evidence for an AGN nature of LRDs. Since most LRDs have not been observed across multiple epochs (unlike the gravitationally lensed and multiply-imaged target A2744-QSO1 Furtak et al. 2025), collecting additional epochs of measurements extending several years will be necessary. The upcoming TWINKLE campaign (JWST Proposal Cycle 4, ID 7404, PI: Naidu) will be the next possibility to find variability in the Balmer emission line fluxes. While expensive, deeper observations of truly AGN-driven LRDs will be crucial to better understand the assembly of supermassive black holes within the first billion years from the Big Bang.

 Author contributions

DDV: Writing – review and editing, Writing – original draft. RJF: Writing – review and editing.

 Acknowledgements

We thank Lukas Furtak and Adi Zitrin for their permission to re-use their figure as shown in our Figure 2. We thank Raphael Hviding for their permission to re-use their figure as shown in our Figure 1. DDV thanks his family for their belief and support throughout the writing process.

 Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

 Generative AI statement

The author(s) declared that generative AI was not used in the creation of this manuscript.

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 References Akins H. B. Casey C. M. Berg D. A. Chisholm J. Cloonan A. P. Franco M. (2025a). Strong rest-uv emission lines in a “little red dot” active galactic nucleus at z = 7: early supermassive Black hole growth alongside compact massive star formation? Astrophysical J. Lett. 980, L29. 10.3847/2041-8213/adab76 Akins H. B. Casey C. M. Chisholm J. Berg D. A. Cooper O. Franco M. (2025b). Tentative detection of neutral gas in a little red dot at z = 4.46. arXiv Preprint arXiv:2503.00998. 10.48550/arXiv.2503.00998 Akins H. B. Casey C. M. Lambrides E. Allen N. Andika I. T. Brinch M. (2025c). Cosmos-web: the overabundance and physical nature of “little red Dots”—Implications for early galaxy and smbh assembly. Astrophysical J. 991, 37. 10.3847/1538-4357/ade984 Ananna T. T. Bogdán Á. Kovács O. E. Natarajan P. Hickox R. C. (2024). X-ray view of little red dots: do they host supermassive Black holes? Astrophysical J. Lett. 969, L18. 10.3847/2041-8213/ad5669 Argyriou I. Glasse A. Law D. R. Labiano A. Álvarez-Márquez J. Patapis P. (2023). Jwst miri flight performance: the medium-resolution spectrometer. Astronomy and Astrophysics 675, A111. 10.1051/0004-6361/202346489 Bagnasco G. Kolm M. Ferruit P. Honnen K. Koehler J. Lemke R. (2007). Overview of the near-infrared spectrograph (nirspec) instrument on-board the james webb space telescope (jwst). Cryog. Optical Systems Instruments XII (SPIE) 6692, 174–187. 10.1117/12.735602 Bao L. Tsai C.-W. Wu J. Wang T. Li G. Assef R. J. (2025). Investigating little red dots with uv excess: are they the high-redshift siblings of blue hot dust-obscured galaxies? Astrophysical J. 992, 117. 10.3847/1538-4357/ae019e Barlow-Hall C. L. Aird J. (2025). Measurements of the z = 4-10 X-ray Luminosity Function: the high space density of moderate-luminosity, obscured AGN. arXiv PrePrint arXiv:2506.16145. 10.48550/arXiv.2506.16145 Barro G. Pérez-González P. G. Kocevski D. D. McGrath E. J. Trump J. R. Simons R. C. (2024). Extremely red galaxies at Z= 5–9 with miri and nirspec: dusty galaxies or obscured active galactic nuclei? Astrophysical J. 963, 128. 10.3847/1538-4357/ad167e Begelman M. C. Dexter J. (2025). Little red dots as late-stage quasi-stars. arXiv Preprint arXiv:2507.09085. 10.48550/arXiv.2507.09085 Bellovary J. (2025). Little red dots are tidal disruption events in runaway-collapsing clusters. Astrophysical J. Lett. 984, L55. 10.3847/2041-8213/adce6c Bezanson R. Labbe I. Whitaker K. E. Leja J. Price S. H. Franx M. (2024). The jwst uncover treasury survey: ultradeep nirspec and nircam observations before the epoch of reionization. Astrophysical J. 974, 92. 10.3847/1538-4357/ad66cf Bouwens R. J. Banados E. Decarli R. Hennawi J. Yang D. Algera H. (2025). Beneath the surface:> 85% of Z> 5.9 qsos in massive host galaxies are uv-faint. arXiv Preprint arXiv:2506. 10.48550/arXiv.2506.24128 Boylan-Kolchin M. (2023). Stress testing λ cdm with high-redshift galaxy candidates. Nat. Astron. 7, 731–735. 10.1038/s41550-023-01937-7 37351007 Brazzini M. D’Odorico V. Bischetti M. Feruglio C. Cupani G. Becker G. (2025). Multi-phase investigation of outflows in the circumgalactic and interstellar media of luminous quasars at z 5. Astronomy and Astrophysics 698, A145. 10.1051/0004-6361/202554010 Brooks M. Simons R. C. Trump J. R. Taylor A. J. Bagley M. B. Backhaus B. (2025). Here there be (dusty) monsters: high-Redshift active galactic nuclei are dustier than their hosts. Astrophysical J. 986, 177. 10.3847/1538-4357/addac4 Carr B. J. Green A. M. (2025). “The history of primordial Black holes,” in Primordial black holes (Springer), 3–33. Carranza-Escudero M. Conselice C. J. Adams N. Harvey T. Austin D. Behroozi P. (2025). Lonely little red dots: challenges to the agn-nature of little red dots through their clustering and spectral energy distributions. arXiv E-Prints. arXiv–2506. 10.48550/arXiv.2506.04004 Casey C. M. Akins H. B. Kokorev V. McKinney J. Cooper O. R. Long A. S. (2024). Dust in little red dots. Astrophysical J. Lett. 975, L4. 10.3847/2041-8213/ad7ba7 Castellano M. Fontana A. Treu T. Santini P. Merlin E. Leethochawalit N. (2022). Early results from glass-jwst. Iii. Galaxy candidates at z 9–15. Astrophysical J. Lett. 938, L15. 10.3847/2041-8213/ac94d0 Chiu H.-H. S. Schive H.-Y. Yang H.-Y. K. Huang H. Gaspari M. (2025). Boosting supermassive Black hole growth in the early universe by fuzzy dark matter solitons. Phys. Rev. Lett. 134, 051402. 10.1103/PhysRevLett.134.051402 39983133 De Graaff A. Brammer G. Weibel A. Lewis Z. Maseda M. V. Oesch P. A. (2025). Rubies: a complete census of the bright and red distant universe with jwst/nirspec. Astronomy and Astrophysics 697, A189. 10.1051/0004-6361/202452186 Delos M. S. Rantala A. Young S. Schmidt F. (2024). Structure formation with primordial Black holes: collisional dynamics, binaries, and gravitational waves. J. Cosmol. Astropart. Phys. 2024 (005), 005. 10.1088/1475-7516/2024/12/005 Durodola E. Pacucci F. Hickox R. C. (2025). Exploring the active galactic nucleus fraction of a sample of jwst’s little red dots at 4< Z< 8: overmassive Black holes are strongly favored. Astrophysical J. 985, 169. 10.3847/1538-4357/adced2 D’Eugenio F. Juodžbalis I. Ji X. Scholtz J. Maiolino R. Carniani S. (2026). Jades and blackthunder: rest-frame balmer-line absorption and the local environment in a little red dot at Z= 5. Mon. Notices R. Astronomical Soc. 545, staf2117. 10.1093/mnras/staf2117 Eisenstein D. J. Willott C. Alberts S. Arribas S. Bonaventura N. Bunker A. J. (2023). Overview of the jwst advanced deep extragalactic survey (jades). arXiv preprint arXiv:2306.02465 Endsley R. Stark D. P. Whitler L. Topping M. W. Chen Z. Plat A. (2023). A jwst/nircam study of key contributors to reionization: the star-forming and ionizing properties of uv-faint z 7- 8 galaxies. Mon. Notices R. Astronomical Soc. 524, 2312–2330. 10.1093/mnras/stad1919 Ferrara A. Pallottini A. Dayal P. (2023). On the stunning abundance of super-early, luminous galaxies revealed by jwst. Mon. Notices R. Astronomical Soc. 522, 3986–3991. 10.1093/mnras/stad1095 Finkelstein S. L. Bagley M. B. Ferguson H. C. Wilkins S. M. Kartaltepe J. S. Papovich C. (2023). Ceers key paper. I. An early look into the first 500 myr of galaxy formation with jwst. Astrophysical Journal Letters 946, L13. 10.3847/2041-8213/acade4 Furtak L. J. Zitrin A. Plat A. Fujimoto S. Wang B. Nelson E. J. (2023). Jwst uncover: extremely red and compact object at z phot 7.6 triply imaged by a2744. Astrophysical J. 952, 142. 10.3847/1538-4357/acdc9d Furtak L. J. Labbé I. Zitrin A. Greene J. E. Dayal P. Chemerynska I. (2024). A high black-hole-to-host mass ratio in a lensed agn in the early universe. Nature 628, 57–61. 10.1038/s41586-024-07184-8 38354833 Furtak L. J. Secunda A. R. Greene J. E. Zitrin A. Labbé I. Golubchik M. (2025). Investigating photometric and spectroscopic variability in the multiply imaged little red dot a2744-qso1. Astronomy and Astrophysics 698, A227. 10.1051/0004-6361/202554110 Gardner J. P. Mather J. C. Abbott R. Abell J. S. Abernathy M. Abney F. E. (2023). The james webb space telescope mission. Publ. Astronomical Soc. Pac. 135, 068001. 10.1088/1538-3873/acd1b5 Gloudemans A. J. Duncan K. J. Eilers A.-C. Farina E. P. Harikane Y. Inayoshi K. (2025). Another piece to the puzzle: radio detection of a jwst-detected active galactic nucleus candidate. Astrophysical J. 986, 130. 10.3847/1538-4357/adddb9 Graham A. W. Chilingarian I. Nguyen D. D. Soria R. Durré M. Forbes D. A. (2025). Dot to dot: high-Z little red dots in diagrams with galaxy-morphology-specific scaling relations, 42. Cambridge: Cambridge University Press. Greene J. E. Labbe I. Goulding A. D. Furtak L. J. Chemerynska I. Kokorev V. (2024). Uncover spectroscopy confirms the surprising ubiquity of active galactic nuclei in red sources at Z> 5. Astrophysical J. 964, 39. 10.3847/1538-4357/ad1e5f Hainline K. N. Maiolino R. Juodžbalis I. Scholtz J. Übler H. d’Eugenio F. (2025). An investigation into the selection and colors of little red dots and active galactic nuclei. Astrophysical J. 979, 138. 10.3847/1538-4357/ad9920 Harikane Y. (2025). Early galaxies and supermassive Black holes discovered by the james webb space telescope. Astrophysics Space Sci. 370, 85. 10.1007/s10509-025-04467-y Hopkins P. F. Murray N. Quataert E. Thompson T. A. (2010). A maximum stellar surface density in dense stellar systems. Mon. Notices R. Astronomical Soc. Lett. 401, L19–L23. 10.1111/j.1745-3933.2009.00777.x Hviding R. E. de Graaff A. Miller T. B. Setton D. J. Greene J. E. Labbé I. (2025). Rubies: a spectroscopic census of little red dots - all point sources with v-shaped continua have broad lines. A&A 702, A57. 10.1051/0004-6361/202555816 Inayoshi K. Maiolino R. (2025). Extremely dense gas around little red dots and high-redshift active galactic nuclei: a nonstellar origin of the balmer break and absorption features. Astrophysical J. Lett. 980, L27. 10.3847/2041-8213/adaebd Inayoshi K. Visbal E. Haiman Z. (2020). The assembly of the first massive Black holes. Annu. Rev. Astronomy Astrophysics 58, 27–97. 10.1146/annurev-astro-120419-014455 Jacak J. E. (2025). Possible nonstellar explanation for the unexpected brightness of the earliest galaxies observed by the james webb space telescope. Sci. Rep. 15, 19204. 10.1038/s41598-025-04418-1 40451867 Jeon J. Bromm V. Liu B. Finkelstein S. L. (2025a). Physical pathways for jwst-observed supermassive Black holes in the early universe. Astrophysical J. 979, 127. 10.3847/1538-4357/ad9f3a Jeon J. Liu B. Bromm V. Fujimoto S. Taylor A. J. Kokorev V. (2025b). Little red dots and their progenitors from direct collapse Black holes. arXiv Preprint arXiv:2508.14155. 10.48550/arXiv.2508.14155 Kannan R. Puchwein E. Smith A. Borrow J. Garaldi E. Keating L. (2025). Introducing the THESAN-ZOOM project: radiation-hydrodynamic simulations of high-redshift galaxies with a multi-phase interstellar medium. Open J. Astrophysics 8. 10.33232/001c.145804 Kashino D. Lilly S. J. Matthee J. Eilers A.-C. Mackenzie R. Bordoloi R. (2023). Eiger. I. A large sample of [o iii]-emitting galaxies at 5.3< Z< 6.9 and direct evidence for local reionization by galaxies. Astrophysical J. 950, 66. 10.3847/1538-4357/acc588 Kido D. Ioka K. Hotokezaka K. Inayoshi K. Irwin C. M. (2025). Black hole envelopes in little red dots. Mon. Notices R. Astronomical Soc. 544, 3407–3416. 10.1093/mnras/staf1898 Kiyuna M. (2026). Super-eddington growth ceiling: analytic constraints on the rapid growth of light-seed Black holes in massive clumps. Mon. Notices R. Astronomical Soc. 545, staf1935. 10.1093/mnras/staf1935 Kiyuna M. Hosokawa T. Chon S. (2024). Sequential formation of supermassive stars and heavy seed bhs through the interplay of cosmological cold accretion and stellar radiative feedback. Mon. Notices R. Astronomical Soc. 534, 3916–3935. 10.1093/mnras/stae2380 Kocevski D. D. Onoue M. Inayoshi K. Trump J. R. Haro P. A. Grazian A. (2023). Hidden little monsters: spectroscopic identification of low-mass, broad-line agns at Z> 5 with ceers. Astrophysical J. Lett. 954, L4. 10.3847/2041-8213/ace5a0 Kocevski D. D. Finkelstein S. L. Barro G. Taylor A. J. Calabrò A. Laloux B. (2024). The rise of faint, red agn at z > 4: a sample of little red dots in the jwst extragalactic legacy fields. arXiv Preprint arXiv:2404.03576. 10.48550/arXiv.2404.03576 Kritos K. Beckmann R. S. Silk J. Berti E. Yi S. Volonteri M. (2025). Supermassive Black hole growth in hierarchically merging nuclear star clusters. Astrophysical J. 991, 58. 10.3847/1538-4357/adeb44 Labbé I. van Dokkum P. Nelson E. Bezanson R. Suess K. A. Leja J. (2023). A population of red candidate massive galaxies˜ 600 myr after the big bang. Nature 616, 266–269. 10.1038/s41586-023-05786-2 36812940 Labbe I. Greene J. E. Bezanson R. Fujimoto S. Furtak L. J. Goulding A. D. (2024). Uncover: candidate red active galactic nuclei at 3< Z< 7 with jwst and alma. Astrophysical J. 978, 92. 10.3847/1538-4357/ad3551 Lahén N. Naab T. Rantala A. Partmann C. (2025). Mergers all the way Down: stellar collisions and kinematics of a dense hierarchically forming massive star cluster in a dwarf starburst. Mon. Notices R. Astronomical Soc. 543, 1023–1038. 10.1093/mnras/staf1546 Lambrides E. Garofali K. Larson R. Ptak A. Chiaberge M. Long A. S. (2024). The case for super-eddington accretion: connecting weak x-ray and uv line emission in jwst broad-line agn during the first gyr of cosmic time. arXiv Preprint. 10.48550/arXiv.2409.13047 Latif M. A. Whalen D. J. (2025). Euclid and roman with jwst could reveal supermassive Black holes at up to z ∼ 15. Astrophysical J. Lett. 990, L58. 10.3847/2041-8213/adfec6 Latif M. A. Aftab A. Whalen D. J. Mezcua M. (2025). Radio emission from little red dots May reveal their true nature. Astronomy and Astrophysics 694, L14. 10.1051/0004-6361/202453194 Li Z. Inayoshi K. Chen K. Ichikawa K. Ho L. C. (2025). Little red dots: rapidly growing Black holes reddened by extended dusty flows. Astrophysical J. 980, 36. 10.3847/1538-4357/ada5fb Lovell C. C. Harrison I. Harikane Y. Tacchella S. Wilkins S. M. (2023). Extreme value statistics of the halo and stellar mass distributions at high redshift: are jwst results in tension with λcdm? Mon. Notices R. Astronomical Soc. 518, 2511–2520. 10.1093/mnras/stac3224 Lu Y. Picker Z. S. Kusenko A. (2024). Direct collapse supermassive Black holes from relic particle decay. Phys. Rev. Lett. 133, 091001. 10.1103/PhysRevLett.133.091001 39270178 Madau P. (2025). Chasing the light: shadowing, collimation, and the super-eddington growth of infant Black holes in jwst-discovered agns. arXiv Preprint arXiv:2501.09854. 10.48550/arXiv.2501.09854 Maiolino R. Risaliti G. Signorini M. Trefoloni B. Juodžbalis I. Scholtz J. (2025). Jwst meets chandra: a large population of compton thick, feedback-free, and intrinsically x-ray weak agn, with a sprinkle of sne. Mon. Notices R. Astronomical Soc. 538, 1921–1943. 10.1093/mnras/staf359 Matthee J. Naidu R. P. Brammer G. Chisholm J. Eilers A.-C. Goulding A. (2024). Little red dots: an abundant population of faint active galactic nuclei at z 5 revealed by the Eiger and fresco jwst surveys. Astrophysical J. 963, 129. 10.3847/1538-4357/ad2345 Mazzolari G. Gilli R. Maiolino R. Prandoni I. Delvecchio I. Norman C. (2024). The radio properties of the JWST-Discovered AGN. Astronomy and Astrophysics 691, A345. 10.1051/0004-6361/202450407 McElwain M. W. Feinberg L. D. Perrin M. D. Clampin M. Mountain C. M. Lallo M. D. (2023). The james webb space telescope mission: optical telescope element design, development, and performance, 135. Cambridge: Cambridge University Press. Naidu R. P. Matthee J. Katz H. de Graaff A. Oesch P. Smith A. (2025). A “black hole star” reveals the remarkable gas-enshrouded hearts of the little red dots. arXiv preprint arXiv:2503.16596 . Natarajan P. Pacucci F. Ricarte A. Bogdán Á. Goulding A. D. Cappelluti N. (2023). First detection of an overmassive Black hole galaxy uhz1: evidence for heavy Black hole seed formation from direct collapse. Astrophysical J. Lett. 960, L1. 10.3847/2041-8213/ad0e76 Oesch P. A. Brammer G. Naidu R. Bouwens R. Chisholm J. Illingworth G. (2023). The jwst fresco survey: legacy nircam/grism spectroscopy and imaging in the two goods fields. Mon. Notices R. Astronomical Soc. 525, 2864–2874. 10.1093/mnras/stad2411 Onoue M. Inayoshi K. Ding X. Li W. Li Z. Molina J. (2023). A candidate for the least-massive Black hole in the first 1.1 billion years of the universe. Astrophysical J. Lett. 942, L17. 10.3847/2041-8213/aca9d3 Pacucci F. Narayan R. (2024). Mildly super-eddington accretion onto slowly spinning Black holes explains the x-ray weakness of the little red dots. Astrophysical J. 976, 96. 10.3847/1538-4357/ad84f7 Pérez-González P. G. Barro G. Rieke G. H. Lyu J. Rieke M. Alberts S. (2024). What is the nature of little red dots and what is not. Astrophysical J. 968 (4). 10.3847/1538-4357/ad38bb Perger K. Fogasy J. Frey S. Gabányi K. (2025). Deep silence: radio properties of little red dots. Astronomy and Astrophysics 693, L2. 10.1051/0004-6361/202452422 Rieke M. J. Kelly D. M. Misselt K. Stansberry J. Boyer M. Beatty T. (2023). Performance of nircam on jwst in flight, 135. Cambridge: Cambridge University Press. Riotto A. Silk J. (2025). The future of primordial Black holes: open questions and roadmap. Singapore: Springer, 691–706. Scholtz J. Maiolino R. D’Eugenio F. Curtis-Lake E. Carniani S. Charlot S. (2025). Jades: a large population of obscured, narrow-line active galactic nuclei at high redshift. Astronomy and Astrophysics 697, A175. 10.1051/0004-6361/202348804 Secunda A. Somerville R. S. Jiang Y.-F. Greene J. E. Furtak L. J. Zitrin A. (2025). Do little red dots vary? Astrophysical J. 996 (6). 10.3847/1538-4357/ae1f08 Setton D. J. Greene J. E. de Graaff A. Ma Y. Leja J. Matthee J. (2024). Little red dots at an inflection point: ubiquitous “v-shaped” turnover consistently occurs at the balmer limit. arXiv Preprint arXiv:2411.03424. 10.48550/arXiv.2411.03424 Setton D. J. Greene J. E. Spilker J. S. Williams C. C. Labbe I. Ma Y. (2025). A confirmed deficit of hot and cold dust emission in the Most luminous little red dots. arXiv preprint arXiv:2503.02059 . Vaccaro M. P. Mapelli M. Périgois C. Barone D. Artale M. C. Dall’Amico M. (2024). Impact of gas hardening on the population properties of hierarchical Black hole mergers in active galactic nucleus disks. Astronomy and Astrophysics 685, A51. 10.1051/0004-6361/202348509 Volonteri M. Habouzit M. Colpi M. (2021). The origins of massive Black holes. Nat. Rev. Phys. 3, 732–743. 10.1038/s42254-021-00364-9 Williams C. C. Alberts S. Ji Z. Hainline K. N. Lyu J. Rieke G. (2024). The galaxies missed by hubble and alma: the contribution of extremely red galaxies to the cosmic census at 3 < z < 8. Astrophysical J. 968, 34. 10.3847/1538-4357/ad3f17 Wootten A. Thompson A. R. (2009). The Atacama large millimeter/submillimeter array. Proc. IEEE 97, 1463–1471. 10.1109/jproc.2009.2020572 Xiao M. Oesch P. A. Bing L. Elbaz D. Matthee J. Fudamoto Y. (2025). No [cii] or dust detection in two little red dots at z spec > 7. A&A 700, A231. 10.1051/0004-6361/202554361 Yue M. Eilers A.-C. Ananna T. T. Panagiotou C. Kara E. Miyaji T. (2024). Stacking x-ray observations of “little red dots”: implications for their active galactic nucleus properties. Astrophysical J. Lett. 974, L26. 10.3847/2041-8213/ad7eba Zhang Z. Jiang L. Liu W. Ho L. C. (2025). Analysis of multi-epoch jwst images of 300 little red dots: tentative detection of variability in a minority of sources. Astrophysical J. 985, 119. 10.3847/1538-4357/adcb3e

Edited by: Emilia Järvelä, Texas Tech University, United States

Reviewed by: Krisztina Perger, Konkoly Observatory (MTA), Hungary

The light from the background LRD travels along paths of different distances which are each gravitationally deflected onto the line of sight. As a result the light arrives at Earth with time delays, since the speed of light is, of course, constant. This same effect can be found by drawing a dot on a piece of graph paper and placing a wine glass’s stem (or base) along the line of sight.