The other side of black holes
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The Other Side of Black Holes
Black Hole Shadows: A Defining Characteristic
Event Horizon and Shadow Formation
A black hole's event horizon is a critical feature that defines its boundary, beyond which nothing can escape. For distant observers, this event horizon casts a "shadow" due to the bending of light around the black hole. This shadow is relatively large, with an apparent diameter of approximately 10 gravitational radii, and is nearly independent of the black hole's spin or orientation1. The shadow's size for Sagittarius A* (Sgr A*), the supermassive black hole at the center of our galaxy, is predicted to be around 30 microarcseconds, which is within the resolution capabilities of current radio interferometers1.
Visual Signature of Black Hole Shadows
The shadow of a black hole is characterized by a sharp-edged dip in brightness, which is the projection of the black hole's unstable-photon region on the observer's sky. This visual signature is produced by two key mechanisms: blocking and path-lengthening. Blocking occurs when rays intersect the unstable-photon region and are absorbed by the event horizon, reducing observed intensity. Path-lengthening happens when rays travel along extended paths near the boundary of the unstable-photon region, increasing observed intensity3. These effects make the black hole shadow a robust and model-independent observable for accreting black holes in low-luminosity active galactic nuclei3.
Wormholes: A Hypothetical Connection
Traversable Wormholes and Their Effects
Wormholes, theoretical passages connecting two different spacetimes, could have significant implications if they exist. In the vicinity of a traversable wormhole, the flux cannot be conserved separately in each space, meaning objects in one space would influence objects in the other. This interaction could be observed in the orbits of stars around the black hole at the center of our galaxy. For instance, a star orbiting Sgr A* on the other side of a wormhole could leave detectable imprints on the orbit of the S2 star on our side, given a future acceleration precision of (10^{-6} m/s^2)2. This effect could also be observed in black hole binary systems or black hole-star binary systems2.
Gravitational Perturbations Across Wormholes
Even non-traversable wormholes could allow gravitational perturbations to be felt on the other side. This means that studying the gravitational interactions around black holes could provide indirect evidence of wormholes, adding another layer of complexity to our understanding of these enigmatic objects2.
Conclusion
The study of black holes and their shadows provides critical insights into the nature of these mysterious objects. The shadow, a distinct visual signature, offers a robust observable for accreting black holes, while the potential existence of wormholes opens up fascinating possibilities for inter-spatial connections and gravitational interactions. As observational techniques advance, we may soon uncover more about the other side of black holes, further expanding our understanding of the universe.
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Most relevant research papers on this topic
Viewing the Shadow of the Black Hole at the Galactic Center
The event horizon of Sgr A*, the Galactic center's black hole, may be observable with submillimeter interferometry within a few years, providing a realistic expectation of imaging the black hole within a few years.
Highly CitedObserving a wormhole
A traversable wormhole connects two different spacetimes, influencing objects in one space and affecting those in the other space, with potential applications in black hole orbits and black hole-star binary systems.
The Nature of Black Hole Shadows
The black hole shadow is a distinct visual signature in black holes, resulting from blocking and path-lengthening effects, making it a robust and fairly model-independent observable for deep sub-Eddington regime black holes.
Classical double copy of nonsingular black holes
Classical double copy procedure can effectively analyze non-singular black hole solutions, revealing a new connection between horizons and electric fields.
Particle creation by black holes
Quantum mechanical effects cause black holes to create and emit particles as if they were hot bodies, leading to their eventual disappearance and violation of the classical law of event horizon area not decreasing.
Highly CitedBlack holes, gravitational waves and fundamental physics: a roadmap
Gravitational-wave astronomy offers a new era of scientific exploration, potentially reshaping our understanding of the cosmos and the laws of Nature.
Highly CitedBlack holes in general relativity
A stationary black hole must have a topologically spherical boundary and be axisymmetric if it is rotating, establishing the conjecture that any stationary black hole is a Kerr solution.
Highly CitedBlack diholes
Black diholes, described in the Einstein-Maxwell equations, are static pairs of oppositely charged extremal black holes suspended in equilibrium in an external magnetic field or held apart by cosmic strings.
Volume inside old black holes
The volume of maximal surfaces inside an evaporating black hole grows monotonically with advanced time, while the area shrinks, potentially impacting the information paradox and remnant scenarios.
The area of a rough black hole
Abstract We investigate the consequences for the black hole area of introducing fractal structure for the horizon geometry. We create a three-dimensional spherical analogue of a ‘Koch Snowflake’ using a infinite diminishing hierarchy of touching spheres around the Schwarzschild event horizon. We can create a fractal structure for the horizon with finite volume and infinite (or finite) area. This is a toy model for the possible effects of quantum gravitational spacetime foam, with significant implications for assessments of the entropy of black holes and the universe, which is generally larger than in standard picture of black hole structure and thermodynamics, potentially by very considerable factors. The entropy of the observable universe today becomes S ≈ 10 120 ( 1 + Δ / 2 ) , where 0 ≤ Δ ≤ 1 , with Δ = 0 for a smooth spacetime structure and Δ = 1 for the most intricate. The Hawking lifetime of black holes is also reduced.
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