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The Event Horizon Telescope (EHT) recently released an image of the supermassive black hole Sgr A* showing an angular shadow diameter $d_{sh}= 48.7 \pm 7\,\mu$as and Schwarzschild shadow deviation $\delta =…

General Relativity and Quantum Cosmology · Physics 2023-02-28 Sushant G. Ghosh , Misba Afrin

The Event Horizon Telescope (EHT) collaboration's image of the compact object at the galactic center is the first direct evidence of the supermassive black hole (BH) Sgr A$^*$. The shadow of Sgr A$^*$ has an angular diameter $d_{sh}= 48.7…

General Relativity and Quantum Cosmology · Physics 2023-02-24 Misba Afrin , Sunny Vagnozzi , Sushant G. Ghosh

The scarcity of quantum gravity (QG) inspired rotating black holes limits the progress of testing QG through Event Horizon Telescope (EHT) observations. The EHT imaged the supermassive black holes, Sgr A* and M87*, revealing an angular…

General Relativity and Quantum Cosmology · Physics 2025-04-30 Heena Ali , Shafqat Ul Islam , Sushant G. Ghosh

The Event Horizon Telescope, a global submillimeter wavelength very long baseline interferometry array, produced the first image of supermassive black hole M87* showing a ring of diameter $\theta_d= 42\pm 3\,\mu$as, inferred a black hole…

General Relativity and Quantum Cosmology · Physics 2020-06-18 Rahul Kumar , Amit Kumar , Sushant G. Ghosh

Recently, the Event Horizon Telescope (EHT) achieved the realization of an image of the supermassive black hole $\textrm{Sgr~A}^\star$ showing an angular shadow diameter $\mathcal{D}= 48.7 \pm 7\mu as$ and the fractional deviation…

General Relativity and Quantum Cosmology · Physics 2024-04-23 L. Chakhchi , H. El Moumni , K. Masmar

The Event Horizon Telescope (EHT) has guided strong-field gravitational physics by providing the first direct images of the supermassive black holes M87* and Sagittarius A*. The EHT observations offer unprecedented opportunities to test…

General Relativity and Quantum Cosmology · Physics 2026-04-16 Towheed Ahmad Nengroo , Shafqat Ul Islam , Sushant G. Ghosh

A mathematically consistent rotating black hole model in loop quantum gravity (LQG) is yet lacking. The scarcity of rotating black hole solutions in LQG substantially hampers the development of testing LQG from observations, e.g., from the…

General Relativity and Quantum Cosmology · Physics 2023-01-25 Shafqat Ul Islam , Jitendra Kumar , Rahul Kumar Walia , Sushant G. Ghosh

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…

High Energy Astrophysical Phenomena · Physics 2023-11-17 The Event Horizon Telescope Collaboration

The Event Horizon Telescope (EHT) collaboration unveiled event-horizon-scale images of the supermassive black holes (SMBHs) M87* and Sgr A*, revealing a dark brightness depression, namely the black hole shadow, whose shape and size may…

General Relativity and Quantum Cosmology · Physics 2023-07-27 Misba Afrin , Sushant G. Ghosh

In general relativity, the angular radius of the shadow of a black hole is primarily determined by its mass-to-distance ratio and depends only weakly on its spin and inclination. If general relativity is violated, however, the shadow size…

The Event Horizon Telescope (EHT), a global submillimeter wavelength very long baseline interferometry array, unveiled event-horizon-scale images of the supermassive black hole M87* as an asymmetric bright emission ring with a diameter of $…

General Relativity and Quantum Cosmology · Physics 2020-05-12 Rahul Kumar , Sushant G. Ghosh

The Event Horizon Telescope (EHT), a global 230 GHz VLBI array, achieves an angular resolution of ${\approx} 20\,\mu{\rm as}$, sufficient to resolve the supermassive black hole Sagittarius A* (Sgr A*). This resolution may soon enable…

Instrumentation and Methods for Astrophysics · Physics 2019-01-09 Ziyan Zhu , Michael D. Johnson , Ramesh Narayan

The Event Horizon Telescope (EHT) observations of Sgr\,A* resolved the shadow image and emission ring-like structure, which is associated to the photon ring of the supermassive black hole, at the galactic centre, revealing a diameter of…

High Energy Astrophysical Phenomena · Physics 2025-04-14 Milton Jair Santibañez-Armenta , Gustavo Magallanes-Guijón , Sergio Mendoza , Alejandro Cruz-Osorio

The M87* black hole shadow observation by the Event Horizon Telescope (EHT) has enabled us to test the modified gravity theories in the extreme-field regime and estimating the black hole parameters. Having this assertion, we investigate the…

General Relativity and Quantum Cosmology · Physics 2023-02-06 Sushant G. Ghosh , Rahul Kumar Walia

We analytically investigate the shadows cast by rotating black holes in the asymptotically safe gravity (ASG) by deriving complete null geodesics and observables using the Hamilton-Jacobi equation and Carter separable method. It turns out…

General Relativity and Quantum Cosmology · Physics 2020-07-13 Rahul Kumar , Balendra Pratap Singh , Sushant G. Ghosh

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…

The Event Horizon Telescope (EHT) has recently observed the image and shadow of the supermassive compact object Sagittarius A$^*$ (Sgr A$^*$). According to the EHT collaboration, the observed image is consistent with the expected appearance…

General Relativity and Quantum Cosmology · Physics 2023-05-29 Rajibul Shaikh

Inspired by the observations of supermassive black hole M87* in \emph{Event Horizon Telescope }(EHT) experiment, a remarkable surge in black hole physics is to use the black hole shadow's observables to distinguish general relativity (GR)…

General Relativity and Quantum Cosmology · Physics 2022-09-20 Yuan Meng , Xiao-Mei Kuang , Zi-Yu Tang

The half opening angle of a Kerr black-hole shadow is always equal to (5+-0.2)GM/Dc^2, where M is the mass of the black hole and D is its distance from the Earth. Therefore, measuring the size of a shadow and verifying whether it is within…

High Energy Astrophysical Phenomena · Physics 2015-12-02 Dimitrios Psaltis , Feryal Ozel , Chi-Kwan Chan , Daniel P. Marrone

The Event Horizon Telescope (EHT) has revealed the horizon-scale radiation of Sagittarius A* (Sgr A*), our galaxy's central supermassive black hole, offering a new platform to test gravitational theories. The next step involves studying…

High Energy Astrophysical Phenomena · Physics 2025-01-16 Kotaro Moriyama , Alejandro Cruz-Osorio , Yosuke Mizuno , Indu K. Dihingia , Akhil Uniyal
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