# Black Holes & Event Horizon Imaging Domain: Astrophysics & Cosmology · 238 papers indexed · newest 2026-10-27 Event Horizon Telescope images of M87* and Sgr A*, polarization and spin measurements and black-hole ringdown tests. Key concepts: Event Horizon Telescope, black hole shadow, Sgr A*, M87, black hole spin, ringdown ## Most influential - **[First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole](https://space-kitty.com/papers/arxiv:1906.11238)**. Kazunori Akiyama, A. Alberdi, W. Alef et al. · 2019 · The Astrophysical Journal Letters (arXiv:1906.11238 · doi:10.3847/2041-8213/ab0ec7 · 4,205 citations). Source: > When surrounded by a transparent emission region, black holes are expected to reveal a dark shadow caused by gravitational light bending and photon capture at the event horizon. To image and study this phenomenon, we have assembled the Event Horizon Telescope, a global very long baseline interferometry array observing at a wavelength of 1.3 mm. This allows us to reconstruct event-horizon-scale images of the supermassive black hole candidate in the center of the giant elliptical galaxy M87. We have resolved the central compact radio source as an asymmetric bright emission ring with a diameter o… - **[First Sagittarius A\* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way](https://space-kitty.com/papers/arxiv:2311.08680)**. Kazunori Akiyama, A. Alberdi, W. Alef et al. · 2022 · The Astrophysical Journal Letters (arXiv:2311.08680 · doi:10.3847/2041-8213/ac6674 · 1,865 citations). Source: > We present the first Event Horizon Telescope (EHT) observations of Sagittarius A\* (Sgr A$^\*$), the Galactic center source associated with a supermassive black hole. These observations were conducted in 2017 using a global interferometric array of eight telescopes operating at a wavelength of $λ=1.3\\,{\\rm mm}$. The EHT data resolve a compact emission region with intrahour variability. A variety of imaging and modeling analyses all support an image that is dominated by a bright, thick ring with a diameter of $51.8 \\pm 2.3$\\,\\uas (68\\% credible interval). The ring has modest azimuthal brightness … - **[First M87 Event Horizon Telescope Results. VI. The Shadow and Mass of the Central Black Hole](https://space-kitty.com/papers/arxiv:1906.11243)**. The Event Horizon Telescope Collaboration · 2019 · ApJ, 875, L6, 2019 (April 10) (arXiv:1906.11243 · doi:10.3847/2041-8213/ab1141 · 1,629 citations). Source: > We present measurements of the properties of the central radio source in M87 using Event Horizon Telescope data obtained during the 2017 campaign. We develop and fit geometric crescent models (asymmetric rings with interior brightness depressions) using two independent sampling algorithms that consider distinct representations of the visibility data. We show that the crescent family of models is statistically preferred over other comparably complex geometric models that we explore. We calibrate the geometric model parameters using general relativistic magnetohydrodynamic (GRMHD) models of the … - **[First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole](https://space-kitty.com/papers/arxiv:1906.11241)**. The Event Horizon Telescope Collaboration · 2019 · ApJ, 875, L4, 2019 (April 10) (arXiv:1906.11241 · doi:10.3847/2041-8213/ab0e85 · 1,501 citations). Source: > We present the first Event Horizon Telescope (EHT) images of M87, using observations from April 2017 at 1.3 mm wavelength. These images show a prominent ring with a diameter of ~40 micro-as, consistent with the size and shape of the lensed photon orbit encircling the "shadow" of a supermassive black hole. The ring is persistent across four observing nights and shows enhanced brightness in the south. To assess the reliability of these results, we implemented a two-stage imaging procedure. In the first stage, four teams, each blind to the others' work, produced images of M87 using both an establ… - **[First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring](https://space-kitty.com/papers/arxiv:1906.11242)**. The Event Horizon Telescope Collaboration · 2019 · ApJ, 875, L5, 2019 (April 10) (arXiv:1906.11242 · doi:10.3847/2041-8213/ab0f43 · 1,427 citations). Source: > The Event Horizon Telescope (EHT) has mapped the central compact radio source of the elliptical galaxy M87 at 1.3 mm with unprecedented angular resolution. Here we consider the physical implications of the asymmetric ring seen in the 2017 EHT data. To this end, we construct a large library of models based on general relativistic magnetohydrodynamic (GRMHD) simulations and synthetic images produced by general relativistic ray tracing. We compare the observed visibilities with this library and confirm that the asymmetric ring is consistent with earlier predictions of strong gravitational lensing… - **[Horizon-scale tests of gravity theories and fundamental physics from the Event Horizon Telescope image of Sagittarius A ∗](https://space-kitty.com/papers/arxiv:2205.07787)**. Sunny Vagnozzi, Rittick Roy, Yu-Dai Tsai et al. · 2023 · Classical and Quantum Gravity (arXiv:2205.07787 · doi:10.1088/1361-6382/acd97b · 748 citations). Source: > Horizon-scale images of black holes (BHs) and their shadows have opened an unprecedented window onto tests of gravity and fundamental physics in the strong-field regime. We consider a wide range of well-motivated deviations from classical General Relativity (GR) BH solutions, and constrain them using the Event Horizon Telescope (EHT) observations of Sagittarius A$^\*$ (Sgr A$^\*$), connecting the size of the bright ring of emission to that of the underlying BH shadow and exploiting high-precision measurements of Sgr A$^\*$'s mass-to-distance ratio. The scenarios we consider, and whose fundamental… - **[First Sagittarius A\* Event Horizon Telescope Results. VI. Testing the Black Hole Metric](https://space-kitty.com/papers/arxiv:2311.09484)**. Kazunori Akiyama, A. Alberdi, W. Alef et al. · 2022 · The Astrophysical Journal Letters (arXiv:2311.09484 · doi:10.3847/2041-8213/ac6756 · 672 citations). Source: > Astrophysical black holes are expected to be described by the Kerr metric. This is the only stationary, vacuum, axisymmetric metric, without electromagnetic charge, that satisfies Einstein's equations and does not have pathologies outside of the event horizon. We present new constraints on potential deviations from the Kerr prediction based on 2017 EHT observations of Sagittarius A\* (Sgr A\*). We calibrate the relationship between the geometrically defined black hole shadow and the observed size of the ring-like images using a library that includes both Kerr and non-Kerr simulations. We use the… - **[Black hole shadows, photon rings, and lensing rings](https://space-kitty.com/papers/arxiv:1906.00873)**. Samuel E. Gralla, DANIEL E. HOLZ, Robert M. Wald · 2019 · Physical review. D/Physical review. D. (arXiv:1906.00873 · doi:10.1103/physrevd.100.024018 · 657 citations). Source: > The presence of a bright "photon ring" surrounding a dark "black hole shadow" has been discussed as an important feature of the observational appearance of emission originating near a black hole. We clarify the meaning and relevance of these heuristics with analytic calculations and numerical toy models. The standard usage of the term "shadow" describes the appearance of a black hole illuminated from all directions, including from behind the observer. A backlit black hole casts a somewhat larger shadow. Neither shadow heuristic is particularly relevant to understanding the appearance of emissi… - **[First Sagittarius A\* Event Horizon Telescope Results. III. Imaging of the Galactic Center Supermassive Black Hole](https://space-kitty.com/papers/arxiv:2311.09479)**. Kazunori Akiyama, A. Alberdi, W. Alef et al. · 2022 · The Astrophysical Journal Letters (arXiv:2311.09479 · doi:10.3847/2041-8213/ac6429 · 449 citations). Source: > We present the first event-horizon-scale images and spatiotemporal analysis of Sgr A\* taken with the Event Horizon Telescope in 2017 April at a wavelength of 1.3 mm. Imaging of Sgr A\* has been conducted through surveys over a wide range of imaging assumptions using the classical CLEAN algorithm, regularized maximum likelihood methods, and a Bayesian posterior sampling method. Different prescriptions have been used to account for scattering effects by the interstellar medium towards the Galactic Center. Mitigation of the rapid intra-day variability that characterizes Sgr A\* has been carried out… - **[Shadows of Kerr Black Holes with Scalar Hair](https://space-kitty.com/papers/arxiv:1509.00021)**. Pedro V. P. Cunha, Carlos Herdeiro, Eugen Radu et al. · 2015 · Physical Review Letters (arXiv:1509.00021 · doi:10.1103/physrevlett.115.211102 · 530 citations). Source: > Using backwards ray tracing, we study the shadows of Kerr black holes with scalar hair (KBHsSH). KBHsSH interpolate continuously between Kerr BHs and boson stars (BSs), so we start by investigating the lensing of light due to BSs. Moving from the weak to the strong gravity region, BSs - which by themselves have no shadows - are classified, according to the lensing produced, as: $(i)$ non-compact, which yield no multiple images; $(ii)$ compact, which produce an increasing number of Einstein rings and multiple images of the whole celestial sphere; $(iii)$ ultra-compact, which possess light rings… - **[Universal interferometric signatures of a black hole’s photon ring](https://space-kitty.com/papers/arxiv:1907.04329)**. Michael D. Johnson, Alexandru Lupsasca, Andrew Strominger et al. · 2020 · Science Advances (arXiv:1907.04329 · doi:10.1126/sciadv.aaz1310 · 410 citations). Source: > The Event Horizon Telescope image of the supermassive black hole in the galaxy M87 is dominated by a bright, unresolved ring. General relativity predicts that embedded within this image lies a thin "photon ring," which is composed of an infinite sequence of self-similar subrings that are indexed by the number of photon orbits around the black hole. The subrings approach the edge of the black hole "shadow," becoming exponentially narrower but weaker with increasing orbit number, with seemingly negligible contributions from high order subrings. Here, we show that these subrings produce strong an… - **[Constraints on black-hole charges with the 2017 EHT observations of M87\*](https://space-kitty.com/papers/arxiv:2105.09343)**. Prashant Kocherlakota, Luciano Rezzolla, Heino D. Falcke et al. · 2021 · Physical review. D/Physical review. D. (arXiv:2105.09343 · doi:10.1103/physrevd.103.104047 · 344 citations). Source: > Our understanding of strong gravity near supermassive compact objects has recently improved thanks to the measurements made by the Event Horizon Telescope (EHT). We use here the M87\* shadow size to infer constraints on the physical charges of a large variety of nonrotating or rotating black holes. For example, we show that the quality of the measurements is already sufficient to rule out that M87\* is a highly charged dilaton black hole. Similarly, when considering black holes with two physical and independent charges, we are able to exclude considerable regions of the space of parameters for t… - **[Hunting for extra dimensions in the shadow of M87\*](https://space-kitty.com/papers/arxiv:1905.12421)**. Sunny Vagnozzi, Luca Visinelli · 2019 · Physical review. D/Physical review. D. (arXiv:1905.12421 · doi:10.1103/physrevd.100.024020 · 364 citations). Source: > The Event Horizon Telescope has recently provided the first image of the dark shadow around the supermassive black hole M87\*. The observation of a highly circular shadow provides strong limits on deviations of M87\*'s quadrupole moment from the Kerr value. We show that the absence of such a deviation can be used to constrain the physics of extra dimensions of spacetime. Focusing on the Randall-Sundrum AdS$\_5$ brane-world scenario, we show that the observation of M87\*'s dark shadow sets the limit $\\ell \\lesssim 170\\,{\\rm AU}$, where $\\ell$ is the AdS$\_5$ curvature radius. This limit is among the… - **[Magnetically charged black holes from non-linear electrodynamics and the Event Horizon Telescope](https://space-kitty.com/papers/arxiv:1912.08231)**. Alireza Allahyari, Mohsen Khodadi, Sunny Vagnozzi et al. · 2020 · Journal of Cosmology and Astroparticle Physics (arXiv:1912.08231 · doi:10.1088/1475-7516/2020/02/003 · 337 citations). Source: > Non-linear electrodynamics (NLED) theories are well-motivated extensions of QED in the strong field regime, and have long been studied in the search for regular black hole (BH) solutions. We consider two well-studied and well-motivated NLED models coupled to General Relativity: the Euler-Heisenberg model and the Bronnikov model. After carefully accounting for the effective geometry induced by the NLED corrections, we determine the shadows of BHs within these two models. We then compare these to the shadow of the supermassive BH M87\* recently imaged by the Event Horizon Telescope collaboration.… - **[Gravitational Test Beyond the First Post-Newtonian Order with the Shadow of the M87 Black Hole](https://space-kitty.com/papers/arxiv:2010.01055)**. Dimitrios Psaltis, Lia Medeiros, Pierre Christian et al. · 2020 · Physical Review Letters (arXiv:2010.01055 · doi:10.1103/physrevlett.125.141104 · 336 citations). Source: > The 2017 Event Horizon Telescope (EHT) observations of the central source in M87 have led to the first measurement of the size of a black-hole shadow. This observation offers a new and clean gravitational test of the black-hole metric in the strong-field regime. We show analytically that spacetimes that deviate from the Kerr metric but satisfy weak-field tests can lead to large deviations in the predicted black-hole shadows that are inconsistent with even the current EHT measurements. We use numerical calculations of regular, parametric, non-Kerr metrics to identify the common characteristic a… ## Newest - **[Testing Conformal Weyl Gravity with Plasma Modified Black Hole Shadows and EHT Constraints](https://space-kitty.com/papers/arxiv:2610.36562)**. Zhichen Guan, Connor McMillin, Owen Gartlan et al. · 2026 (arXiv:2610.36562). Source: - **[A Collimated Protostellar Outflow Likely Driven by Jet and Reshaped by Environment in the Sagittarius C Cloud of the Central Molecular Zone](https://space-kitty.com/papers/arxiv:2610.36573)**. Sen-Di Bo, Xing Lu, Tian-Yu Tu et al. · 2026 (arXiv:2610.36573). Source: - **[Improved constraints on higher-derivative effective field theory extensions of general relativity with GW230627\_015337](https://space-kitty.com/papers/arxiv:2610.36728)**. Tao Zhu · 2026 (arXiv:2610.36728). Source: - **[Self lensing in BH-NS binaries as progenitors for periodically repeating Fast Radio Bursts](https://space-kitty.com/papers/arxiv:2610.37052)**. L. E. Rodríguez, M. Cruces, G. Voisin et al. · 2026 (arXiv:2610.37052). Source: - **[Tidal contributions to neutron star orbital precession around Sgr $A^\*$](https://space-kitty.com/papers/arxiv:2610.35776)**. H Lalrinfela, P. C. Lalremruati, Zodinmawia et al. · 2026 (arXiv:2610.35776). Source: - **[Can a Wormhole Induce a Monopole?](https://space-kitty.com/papers/arxiv:2610.35969)**. Sergei Slobodov · 2026 (arXiv:2610.35969). Source: - **[Late Epoch Infrared Spectroscopy and Two-Component 3D Photoionization Modeling of Classical Nova V5668 Sgr](https://space-kitty.com/papers/arxiv:2610.33376)**. Sarah H. Taft, Charles E. Woodward, Bruno C. Santos et al. · 2026 (arXiv:2610.33376). Source: - **[Gravitational Waves from Ringing Dyonic Black Holes and Estimation of Parameters in Einstein-Bumblebee-Maxwell Gravity](https://space-kitty.com/papers/arxiv:2610.33569)**. Sikha Gogoi, Umananda Dev Goswami · 2026 (arXiv:2610.33569). Source: - **[Perturbations and phenomenology of compact objects in quantum gravity theories](https://space-kitty.com/papers/arxiv:2610.31536)**. Andrea Spina · 2026 (arXiv:2610.31536). Source: - **[Image Morphology of Misaligned Magnetically Arrested Disks](https://space-kitty.com/papers/arxiv:2610.31754)**. Samuel Feyan, Cora Prather, Dominic O. Chang et al. · 2026 (arXiv:2610.31754). Source: --- Space Kitty Archive · https://space-kitty.com · API: https://space-kitty.com/api/v1 · MCP: https://space-kitty.com/mcp · Premium: $0.20/request via x402 (Base Sepolia (testnet)). Metadata: arXiv (CC0), OpenAlex (CC0), Europe PMC (CC BY/CC0 works), ClinicalTrials.gov.