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Submillimeter interferometry has the potential to image supermassive black holes on event horizon scales, providing tests of the theory of general relativity and increasing our understanding of black hole accretion processes. The Event…

The black hole in the center of the Galaxy, associated with the compact source Sagittarius A* (Sgr A*), is predicted to cast a shadow upon the emission of the surrounding plasma flow, which encodes the influence of general relativity in the…

The Event Horizon Telescope is a global very-long baseline interferometer capable of probing potential deviations from the Kerr metric, which is believed to provide the unique description of astrophysical black holes. Here we report an…

High Energy Astrophysical Phenomena · Physics 2016-09-02 Tim Johannsen , Carlos Wang , Avery E. Broderick , Sheperd S. Doeleman , Vincent L. Fish , Abraham Loeb , Dimitrios Psaltis

(abridged) The black hole Sagittarius A* (Sgr A*) is a prime target for next-generation Earth-space very-long-baseline interferometry missions such as the Black Hole Explorer (BHEX), which aims to probe baselines of the order of 20…

High Energy Astrophysical Phenomena · Physics 2025-07-16 Aditya Tamar , Ben Hudson , Daniel C. M. Palumbo

An initial three-station version of the Event Horizon Telescope, a millimeter-wavelength very-long baseline interferometer, has observed Sagittarius A* (Sgr A*) repeatedly from 2007 to 2013, resulting in the measurement of a variety of…

AMIGO is a first-generation Astrodynamical Middle-frequency Interferometric GW Observatory. The scientific goals of AMIGO are: to bridge the spectra gap between first-generation high-frequency and low-frequency GW sensitivities; to detect…

General Relativity and Quantum Cosmology · Physics 2020-07-14 Wei-Tou Ni , Gang Wang , An-Ming Wu

Very-long-baseline interferometry (VLBI) at frequencies above 230 GHz with Earth-diameter baselines gives spatial resolution finer than the ${\sim}50 \mu$as "shadow" of the supermassive black hole at the Galactic Center, Sagittarius A* (Sgr…

Instrumentation and Methods for Astrophysics · Physics 2019-08-21 Daniel C. M. Palumbo , Sheperd S. Doeleman , Michael D. Johnson , Katherine L. Bouman , Andrew A. Chael

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…

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

It has been proposed that Very Long Baseline Interferometry (VLBI) at sub-millimeter waves will allow us to image the shadow of the black hole in the center of our Milky Way, Sagittarius A* (Sgr A*), and thereby test basic predictions of…

The microhertz frequency band of gravitational waves probes the merger of supermassive black holes as well as many other gravitational wave phenomena. However, space-interferometry methods that use test masses would require further…

Instrumentation and Methods for Astrophysics · Physics 2025-09-29 Matthew McQuinn , Casey McGrath

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

Interferometry provides one of the possible routes to ultra-high angular resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular resolution, necessary to achieve objectives such as imaging the regions around the event…

Instrumentation and Methods for Astrophysics · Physics 2009-07-31 G. K. Skinner , J. F. Krizmanic

We consider the application of interferometry to measuring the sizes and shapes of small bodies in the solar system that cannot be spatially resolved by today's single-dish telescopes. Assuming ellipsoidal shapes, our results indicate that…

Earth and Planetary Astrophysics · Physics 2011-02-07 Jian-Yang Li , Marc J. Kuchner , Ronald J. Allen , Scott S. Sheppard

Precision measurements of the stars in short-period orbits around the supermassive black hole at the Galactic Center are now being used to constrain general relativistic effects, such as the gravitational redshift and periapse precession.…

General Relativity predicts that the emission close to a black hole must be lensed by its strong gravitational field, illuminating the last photon orbit. This results in a dark circular area known as the black hole 'shadow'. The Event…

Instrumentation and Methods for Astrophysics · Physics 2016-09-02 Leonid Benkevitch , Kazunori Akiyama , Rusen Lu , Shepherd Doeleman , Vincent Fish

We propose a new imaging technique for radio and optical/infrared interferometry. The proposed technique reconstructs the image from the visibility amplitude and closure phase, which are standard data products of short-millimeter very long…

Global MCAO aims to exploit a very wide technical field of view to find AO-suitable NGSs, with the goal to increase the overall sky coverage. The concept foresees the use of numerical entities, called Virtual Deformable Mirrors, to deal…

Instrumentation and Methods for Astrophysics · Physics 2018-08-02 Valentina Viotto , Elisa Portaluri , Roberto Ragazzoni , Carmelo Arcidiacono , Maria Bergomi , Marco Dima , Jacopo Farinato , Davide Greggio , Demetrio Magrin

The NASA STEREO mission opened up the possibility to forecast the arrival times, speeds and directions of solar transients from outside the Sun-Earth line. In particular, we are interested in predicting potentially geo-effective…

Solar and Stellar Astrophysics · Physics 2015-06-04 Christian Möstl , Jackie A. Davies

Interferometers, such as the Event Horizon Telescope (EHT), do not directly observe the images of sources but rather measure their Fourier components at discrete spatial frequencies up to a maximum value set by the longest baseline in the…

High Energy Astrophysical Phenomena · Physics 2020-04-15 Dimitrios Psaltis , Lia Medeiros , Tod R. Lauer , Chi-Kwan Chan , Feryal Ozel

The petaling effect, induced by pupil fragmentation from the telescope spider, drastically affects the performance of high contrast instruments by inducing core splitting on the PSF. Differential piston/tip/tilt aberrations within each…

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