No observational proof of the black-hole event-horizon

By Marek Abramowicz, W. Kluźniak, Jan Lasota. 2002

221 citations recorded by the source corpus.

Recently, several ways of verifying the existence of black-hole horizons have been proposed. We show here that most of these suggestions are irrelevant to the problem of the horizon, at best they can rule out the presence of conventional baryonic matter in the outer layers of black-hole candidates. More generally, we argue that it is fundamentally impossible to detect in electromagnetic radiation direct evidence for the presence of a black-hole horizon. This applies also to future observations, which would trace very accurately the details of the space-time metric of a body suspected of being a black hole. Specific solutions of Einsteins's equations lack an event horizon, and yet are indistinguishable in their electromagnetic signature from Schwarzschild black holes.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/543a40fbd46eb10397817bed4965eebedab169e0

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Citations in the corpus

Hot Accretion Flows Around Black Holes (2014, background): “…(Narayan et al. 1998a, Broderick & Narayan 2006, Narayan & McClintock 2008, Broderick et al. 2009; see also Narayan et al. 1997b, Menou et al. 1999a, Garcia et al. 2001, McClintock et al. 2004 for related arguments in the case of quiescent BHBs, and Abramowicz et al. 2002b for a counter-argument).”
Superradiance: Energy Extraction, Black-Hole Bombs and Implications for Astrophysics and Particle Physics (2015, background): “Such tests are extremely challenging to perform in the optical window and, in fact, some claims exist [526] that performing these tests might even be intrinsically impossible.”
Stable gravastars—an alternative to black holes? (2004, background): “Such dissent ranges from a careful sceptical analysis of what it physically means to observe an event horizon [1], through alternative models for compact objects [2], to more radical proposals that drastically modify the physics in the region where the event horizon would otherwise be expected to fo”
Measuring the Kerr spin parameter of regular black holes from their shadow (2013, background): “The non-observation of electromagnetic radiation emitted by the possible surface of these objects may also be interpreted as an indication for the existence of an event horizon [11, 12] (but see [13, 14]).”
Testing black hole candidates with electromagnetic radiation (2015, background): “See also Abramowicz et al. (2002) and Bambi (2013b) on this point.”
How to tell a gravastar from a black hole (2007, unknown): “Nx”
INTO THE LAIR: GRAVITATIONAL-WAVE SIGNATURES OF DARK MATTER (2013, background): “In fact, some argue that an observational proof of the event horizon based only on electromagnetic observation is fundamentally impossible (Abramowicz et al. 2002).”
The Gravitational-Wave Physics (2017, background): “Is it possible the black hole horizon be replaced with other objects such as firewall or anything else? Or any experiments present evidence that black hole horizon really exists? Unfortunately, one cannot get observational proof of the existence of a black hole event horizon based on EM waves [142].”
Superradiance (2015, background): “Such tests are extremely challenging to perform in the electromagnetic window [706, 703, 609].”
Tests for the existence of black holes through gravitational wave echoes (2017, background): “[144, 145], concluding that “it is fundamentally impossible to give an observational proof for the existence of a BH horizon.”
Constraining the spin and the deformation parameters from the black hole shadow (2014, background): “The non-observation of electromagnetic radiation emitted by the possible surface of these objects may also be interpreted as an indication for the existence of an event horizon [29, 30] (but see [31, 32]).”