4. Falling into a black hole …

2015 ◽  
Author(s):  
Katherine Blundell
Keyword(s):  
Black Hole ◽  
Event Horizon ◽  
Time Dilation ◽  
Gravitational Redshift ◽  
Black Hole Mass ◽  
Spin Direction ◽  
Tidal Forces ◽  
Particle Orbits

‘Falling into a black hole … considers what happens near to a black hole and how close is too close to avoid an object being pulled into the black hole. Gravitational redshift arises where spacetime is stretched out or curved by the effect of a black hole and time dilation is the effect of time ‘running more slowly’ moving closer to a black hole. These effects are larger if the black hole mass is larger, and also become more extreme the closer you get to the event horizon. The effect of spin and spin direction on how close particles may encounter the black hole, dynamic spacetime, tidal forces, and particle orbits are also considered.

scholarly journals Universal interferometric signatures of a black hole’s photon ring

2020 ◽  
Vol 6 (12) ◽  
pp. eaaz1310 ◽  
Author(s):  
Michael D. Johnson ◽  
Alexandru Lupsasca ◽  
Andrew Strominger ◽  
George N. Wong ◽  
Shahar Hadar ◽  
...  
Keyword(s):  
General Relativity ◽  
Black Hole ◽  
Event Horizon ◽  
Infinite Sequence ◽  
High Order ◽  
Black Hole Mass ◽  
Tests Of General Relativity ◽  
Supermassive Black Hole ◽  
The Galaxy ◽  
Self Similar

The Event Horizon Telescope image of the supermassive black hole in the galaxy M87 is dominated by a bright, unresolved ring. General relativity predicts that embedded within this image lies a thin “photon ring,” which is composed of an infinite sequence of self-similar subrings that are indexed by the number of photon orbits around the black hole. The subrings approach the edge of the black hole “shadow,” becoming exponentially narrower but weaker with increasing orbit number, with seemingly negligible contributions from high-order subrings. Here, we show that these subrings produce strong and universal signatures on long interferometric baselines. These signatures offer the possibility of precise measurements of black hole mass and spin, as well as tests of general relativity, using only a sparse interferometric array.

scholarly journals The shadow of M87∗ black hole within rational nonlinear electrodynamics

2020 ◽  
Vol 35 (35) ◽  
pp. 2050291
Author(s):  
S. I. Kruglov
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Black Hole ◽  
Event Horizon ◽  
Magnetic Charge ◽  
Nonlinear Electrodynamics ◽  
Black Hole Mass

We consider rational nonlinear electrodynamics with the Lagrangian [Formula: see text] ([Formula: see text] is the Lorentz invariant), proposed in Ref. 63, coupled to General Relativity. The effective geometry induced by nonlinear electrodynamics corrections are found. We determine shadow’s size of regular non-rotating magnetic black holes and compare them with the shadow size of the super-massive M87[Formula: see text] black hole imaged by the Event Horizon Telescope collaboration. Assuming that the black hole mass has a pure electromagnetic nature, we obtain the black hole magnetic charge. The size of the shadow obtained is very close to the shadow size of non-regular neutral Schwarzschild black holes. As a result, we can interpret the super-massive M87[Formula: see text] black hole as a regular (without singularities) magnetized black hole.

BLACK HOLES, THE GENERALIZED UNCERTAINTY PRINCIPLE AND HIGHER DIMENSIONS

2013 ◽  
Vol 28 (03) ◽  
pp. 1340011 ◽  
Author(s):  
B. J. CARR
Keyword(s):  
Black Holes ◽  
Black Hole ◽  
Event Horizon ◽  
Uncertainty Principle ◽  
Black Hole Solution ◽  
Generalized Uncertainty Principle ◽  
Black Hole Mass ◽  
Compton Wavelength ◽  
Planck Mass ◽  
Spatial Dimensions

We propose a new way in which black holes connect macrophysics and microphysics. The Generalized Uncertainty Principle suggests corrections to the Uncertainty Principle as the energy increases towards the Planck value. It also provides a natural transition between the expressions for the Compton wavelength below the Planck mass and the black hole event horizon size above it. This suggests corrections to the event horizon size as the black hole mass falls towards the Planck value, leading to the concept of a Generalized Event Horizon. Extrapolating this expression below the Planck mass suggests the existence of a new kind of black hole, whose size is of order its Compton wavelength. Recently it has been found that such a black hole solution is permitted by loop quantum gravity, its unusual properties deriving from the fact that it is hidden behind the throat of a wormhole. This has important implications for the formation and evaporation of black holes in the early Universe, especially if there are extra spatial dimensions.

Tristimania

2017 ◽  
Author(s):  
Jay Griffiths
Keyword(s):  
Black Hole ◽  
Force Field ◽  
Event Horizon ◽  
Personal Experience ◽  
Human Life ◽  
Time Dilation ◽  
Infinite Time ◽  
Depressed State ◽  
Sense Of Time

This chapter uses theBlack Hole as a metaphor for depression based on personal experience with the disease. Like a Black Hole, depression consumes and contorts time. Depression sucks an entire human life into itself, the chapter states. Nothing can withstand its relentless tug into sheer black nothingness; it is a force field of pure negativity, a Black Hole. Depression slows one’s sense of time as—in what is called ‘gravitational time dilation’—an object falling into a Black Hole appears to slow down as it approaches the event horizon, taking an infinite time to reach it. The chapter describes the condition when in a depressed state and says depression is an illness which seems to punish the sufferer with isolation, noting that isolation is different from loneliness and solitude. The chapter also suggests that animals are like the opposite of a Black Hole; for example, cats can be extremely important to someone who is depressed.

scholarly journals Toward the Gravitational Redshift Detection in NGC 4258 and the Estimation of Its Black Hole Mass-to-distance Ratio

2021 ◽  
Vol 917 (1) ◽  
pp. L14
Author(s):  
Ulises Nucamendi ◽  
Alfredo Herrera-Aguilar ◽  
Raúl Lizardo-Castro ◽  
Omar López-Cruz
Keyword(s):  
Black Hole ◽  
Gravitational Redshift ◽  
Black Hole Mass ◽  
Distance Ratio

scholarly journals Hawking evaporation cascade in the presence of backreaction effect

2017 ◽  
Vol 32 (16) ◽  
pp. 1750088 ◽  
Author(s):  
Avik Paul ◽  
Bibhas Ranjan Majhi
Keyword(s):  
Black Hole ◽  
Emission Spectrum ◽  
Event Horizon ◽  
Hawking Radiation ◽  
Space Time ◽  
Black Hole Mass ◽  
Planck Mass ◽  
Black Hole Background ◽  
Continuous Radiation ◽  
Physical Background

We study the cascade of Hawking emission spectrum from the event horizon in the presence of one loop backreaction effect in a black hole background. The space–time taken here is the modified Schwarzschild one. The analysis shows that it is possible to decrease the sparsity with the decrease in black hole mass. Moreover, at some particular value of mass, one has a continuous radiation cascade. This result is completely new and quite different from the usual one. An estimation of the mass for continuous one is also found. We see that the value is of the Planck mass order. In this process, it is observed that under a physical background, below a particular value of the mass, the Hawking radiation must stop and we have a remnant. This was absent in the earlier analysis.

The Equivalence Principle

2018 ◽  
Author(s):  
David M. Wittman
Keyword(s):  
General Relativity ◽  
Special Relativity ◽  
Equivalence Principle ◽  
Time Dilation ◽  
Gravitational Redshift ◽  
Coordinate Systems ◽  
Spacetime Metric

The equivalence principle is an important thinking tool to bootstrap our thinking from the inertial coordinate systems of special relativity to the more complex coordinate systems that must be used in the presence of gravity (general relativity). The equivalence principle posits that at a given event gravity accelerates everything equally, so gravity is equivalent to an accelerating coordinate system.This conjecture is well supported by precise experiments, so we explore the consequences in depth: gravity curves the trajectory of light as it does other projectiles; the effects of gravity disappear in a freely falling laboratory; and gravitymakes time runmore slowly in the basement than in the attic—a gravitational form of time dilation. We show how this is observable via gravitational redshift. Subsequent chapters will build on this to show how the spacetime metric varies with location.

scholarly journals X-Ray Determination of the Black-Hole Mass in Cygnus X-1

1998 ◽  
Vol 188 ◽  
pp. 388-389
Author(s):  
A. Kubota ◽  
K. Makishima ◽  
T. Dotani ◽  
H. Inoue ◽  
K. Mitsuda ◽  
...  
Keyword(s):  
Black Hole ◽  
Compact Object ◽  
Optical Observations ◽  
Black Hole Mass ◽  
X Ray ◽  
Upper Limit ◽  
Supergiant Star ◽  
X Ray Binaries ◽  
Two Bodies

About 10 X-ray binaries in our Galaxy and LMC/SMC are considered to contain black hole candidates (BHCs). Among these objects, Cyg X-1 was identified as the first BHC, and it has led BHCs for more than 25 years(Oda 1977, Liang and Nolan 1984). It is a binary system composed of normal blue supergiant star and the X-ray emitting compact object. The orbital kinematics derived from optical observations indicates that the compact object is heavier than ~ 4.8 M⊙ (Herrero 1995), which well exceeds the upper limit mass for a neutron star(Kalogora 1996), where we assume the system consists of only two bodies. This has been the basis for BHC of Cyg X-1.

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