BlackHoleCam: Fundamental physics of the galactic center

By C. Goddi, Heino Falcke, M. Kramer, Luciano Rezzolla, C. Brinkerink, T. Bronzwaer, J. Davelaar, R. Deane, M. D. Laurentis, G. Desvignes and 29 more. 2016

167 citations recorded by the source corpus.

Einstein’s General theory of relativity (GR) successfully describes gravity. Although GR has been accurately tested in weak gravitational fields, it remains largely untested in the general strong field cases. One of the most fundamental predictions of GR is the existence of black holes (BHs). After the recent direct detection of gravitational waves by LIGO, there is now near conclusive evidence for the existence of stellar-mass BHs. In spite of this exciting discovery, there is not yet direct evidence of the existence of BHs using astronomical observations in the electromagnetic spectrum. Are BHs observable astrophysical objects? Does GR hold in its most extreme limit or are alternatives needed? The prime target to address these fundamental questions is in the center of our own Milky Way, which hosts the closest and best-constrained supermassive BH candidate in the universe, Sagittarius A* (Sgr A*). Three different types of experiments hold the promise to test GR in a strong-field regime using observations of Sgr A* with new-generation instruments. The first experiment consists of making a standard astronomical image of the synchrotron emission from the relativistic plasma accreting onto Sgr A*. This emission forms a “shadow” around the event horizon cast against the background, whose predicted size (∼50μas) can now be resolved by upcoming very long baseline radio interferometry experiments at mm-waves such as the event horizon telescope (EHT). The second experiment aims to monitor stars orbiting Sgr A* with the next-generation near-infrared (NIR) interferometer GRAVITY at the very large telescope (VLT). The third experiment aims to detect and study a radio pulsar in tight orbit about Sgr A* using radio telescopes (including the Atacama large millimeter array or ALMA). The BlackHoleCam project exploits the synergy between these three different techniques and contributes directly to them at different levels. These efforts will eventually enable us to measure fundamental BH parameters (mass, spin, and quadrupole moment) with sufficiently high precision to provide fundamental tests of GR (e.g. testing the no-hair theorem) and probe the spacetime around a BH in any metric theory of gravity. Here, we review our current knowledge of the physical properties of Sgr A* as well as the current status of such experimental efforts towards imaging the event horizon, measuring stellar orbits, and timing pulsars around Sgr A*. We conclude that the Galactic center provides a unique fundamental-physics laboratory for experimental tests of BH accretion and theories of gravity in their most extreme limits.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/865c1ca95804e796a3c5bbfc27dfd01fd639f5fc

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Astronomy and Astrophysics

In Instrumentation

Citations in the corpus

Gravitational Lensing in Presence of Plasma: Strong Lens Systems, Black Hole Lensing and Shadow (2017, background): “Numerous analytical investigations and numerical simulations of the shadow are presented in literature (for example, see [90, 101, 95, 85, 86, 103, 104, 105, 94, 98, 99, 91, 106, 102, 97, 87, 88, 89, 93, 92, 96, 100, 110, 107, 108, 109, 111]).”
Shadows and deflection angle of charged and slowly rotating black holes in Einstein-Æther theory (2019, methodology): “Future improvement of the observations, such as those together with the the Next Generation Very Large Array [3], the Thirty Meter Telescope [4], and BlackHoleCam [5], can provide more precise and details information about the nature of the black hole spacetime in the regime of strong gravity.”
The current ability to test theories of gravity with black hole shadows (2018, unknown): “  I K SSIM( , ) : 2 2 2 2 (4) I K”
Phenomenological aspects of black holes beyond general relativity (2018, background): “, [151]) will certainly improve our understanding of the environment of Sgr A* and will allow more accurate measurements of its accretion rate [152, 153], which would increase the accuracy of the constraints that follow from other observational channels and which have been described above in this se”
Shadow and quasinormal modes of a rotating loop quantum black hole (2020, methodology): “Future improvements of the observations, such as those from the Next Generation Very Large Array [7], the Thirty Meter Telescope [8], and BlackHoleCam [9], can provide unique opportunities for us to get deep insight on the nature of black hole spacetimes in the regime of strong gravity.”
Tests for the existence of black holes through gravitational wave echoes (2017, unknown): “Imaging these shadows for the supermassive dark source SgrA∗ at the center of our galaxy is the main goal of the Event Horizon Telescope [5, 6].”