Penrose process

Short description: Hypothetical mechanism for extracting energy from rotating black holes

The Penrose process (also called Penrose mechanism) is theorised by Sir Roger Penrose as a means whereby energy can be extracted from a rotating black hole.[1][2][3] The process takes advantage of the ergosphere – a region of spacetime around the black hole dragged by its rotation faster than the speed of light, meaning that from the point of view of an outside observer any matter inside is forced to move in the direction of the rotation of the black hole.[4]

Trajectories of bodies in a Penrose process

In the process, a working body falls (black thick line in the figure) into the ergosphere (gray region). At its lowest point (red dot) the body fires a propellant backwards; however, to a faraway observer both seem to continue to move forward due to frame-dragging (albeit at different speeds). The propellant, being slowed, falls (thin gray line) to the event horizon of the black hole (black disk). The remains of the body, being sped up, fly away (thin black line) with an excess of energy (that more than offsets the loss of the propellant and the energy used to shoot it).

The maximum amount of energy gain possible for a single particle decay via the original (or classical) Penrose process is 20.7% of its mass in the case of an uncharged black hole (assuming the best case of maximal rotation of the black hole).[5] The energy is taken from the rotation of the black hole, so there is a limit on how much energy one can extract by Penrose process and similar strategies (for an uncharged black hole no more than 29% of its original mass;[6] larger efficiencies would be possible for charged rotating black holes[7]).

## Contents

* 1 Details of the ergosphere
* 2 In popular culture
* 3 See also
* 4 References
* 5 Further reading

## Details of the ergosphere

The outer surface of the ergosphere is the surface at which light that moves in the direction opposite to the rotation of the black hole remains at a fixed angular coordinate, according to an external observer. Since massive particles necessarily travel slower than light, massive particles will necessarily move along with the black hole's rotation. The inner boundary of the ergosphere is the event horizon, the spatial perimeter beyond which light cannot escape.

Inside the ergosphere even light cannot keep up with the rotation of the black hole, as the trajectories of stationary (from the outside perspective) objects become space-like, rather than time-like (that normal matter would have), or light-like. Mathematically, the dt2 component of the metric changes its sign inside the ergosphere. That allows matter to have negative energy inside of the ergosphere as long as it moves counter the black hole's rotation fast enough (or, from outside perspective, resists being dragged along to a sufficient degree). The Penrose mechanism exploits that by diving into the ergosphere, dumping an object that was given negative energy, and returning with more energy than before.

In this way, rotational energy is extracted from the black hole, resulting in the black hole being spun down to a lower rotational speed. The maximum amount of energy (per mass of the thrown in object) is extracted if the black hole is rotating at the maximal rate, the object just grazes the event horizon and decays into forwards and backwards moving packets of light (the first escapes the black hole, the second falls inside).[5]

In an adjunct process, a black hole can be spun up (its rotational speed increased) by sending in particles that do not split up, but instead give their entire angular momentum to the black hole. However, this is not a reverse of the Penrose process, as both increase the entropy of the black hole by throwing material into it.

## In popular culture

Dominic Green's 2005 short story "The Clockwork Atom Bomb" involves the use of the Penrose Process for military applications and power generation.

A major plot point of the 2014 science fiction film Interstellar is the use of the Penrose process to slingshot the spacecraft Endurance towards Edmund's planet flying through the ergosphere of fictional black hole Gargantua.

In the narrative of 2024 cooperative horde shooter game Helldivers 2, the Penrose process was utilized to decrease the velocity of a singularity.[8]

## See also

* Astronomy:Blandford–Znajek process - Explanation for how quasars are powered
* Physics:Hawking radiation - Thermal radiation believed to be emitted by black holes due to quantum effects
* High Life, a 2018 science-fiction film that includes a mission to harness the process
* Astronomy:Black hole bomb - Physical effect when superradiant modes are confined around a rotating black hole
* Astronomy:Hills mechanism - Black hole effect on a binary star

## References

1. ↑ Penrose, R.; Floyd, R. M. (February 1971). "Extraction of Rotational Energy from a Black Hole" (in en). Nature Physical Science 229 (6): 177–179. doi:10.1038/physci229177a0. ISSN 0300-8746. Bibcode: 1971NPhS..229..177P.
2. ↑ Misner, Charles W.; Thorne, Kip S.; Wheeler, John Archibald (1973). Gravitation. San Francisco: W. H. Freeman. ISBN 978-0-7167-0334-1. Misner, Thorne, and Wheeler, Gravitation, Freeman and Company, 1973.
3. ↑ Williams, R. K. (1995). "Extracting X rays, Ύ rays, and relativistic e−e+ pairs from supermassive Kerr black holes using the Penrose mechanism". Physical Review D 51 (10): 5387–5427. doi:10.1103/PhysRevD.51.5387. PMID 10018300. Bibcode: 1995PhRvD..51.5387W.
4. ↑ Cui, Yuzhu et al. (2023). "Precessing jet nozzle connecting to a spinning black hole in M87". Nature 621 (7980): 711–715. doi:10.1038/s41586-023-06479-6. PMID 37758892. Bibcode: 2023Natur.621..711C.
5. ↑ 5.0 5.1 Chandrasekhar, Subrahmanyan (1983). The Mathematical Theory of Black Holes. Clarendon Press. pp. 369. ISBN 0-19-851291-0. Bibcode: 1983mtbh.book.....C.
6. ↑ Carroll 2004, p. 271 harvnb error: no target: CITEREFCarroll2004 (help)
7. ↑ Bhat, Manjiri; Dhurandhar, Sanjeev; Dadhich, Naresh (1985). "Energetics of the Kerr-Newman black hole by the penrose process". Journal of Astrophysics and Astronomy 6 (2): 85–100. doi:10.1007/BF02715080. Bibcode: 1985JApA....6...85B.
8. ↑ "Major Orders" (in en). https://helldivers.wiki.gg/wiki/Major_Orders#A2-3-5.

## Further reading

* Chandrasekhar, Subrahmanyan (1998). The Mathematical Theory of Black Holes. Oxford classic texts in the physical sciences. Oxford University Press. ISBN 978-0-19-850370-5.
* Carroll, Sean M. (2003). Spacetime and geometry: an introduction to general relativity. San Francisco: Addison-Wesley. ISBN 978-0-8053-8732-2. OCLC ocm53245141.

* v
* t
* e

Black holes

Types|

* Schwarzschild
* Rotating
* Charged
* Virtual
* Kugelblitz
* Primordial
* Planck particle

Size|

* Micro
* Extremal
* Electron
* Stellar
* Microquasar
* Intermediate-mass
* Supermassive
* Active galactic nucleus
* Quasar
* Blazar

Formation|

* Stellar evolution
* Gravitational collapse
* Neutron star
* Related links
* Tolman–Oppenheimer–Volkoff limit
* White dwarf
* Related links
* Supernova
* Related links
* Hypernova
* Gamma-ray burst
* Binary black hole

Properties|

* Gravitational singularity
* Ring singularity
* Theorems
* Event horizon
* Photon sphere
* Innermost stable circular orbit
* Ergosphere
* Penrose process
* Blandford–Znajek process
* Accretion disk
* Hawking radiation
* Gravitational lens
* Bondi accretion
* M–sigma relation
* Quasi-periodic oscillation
* Thermodynamics
* Immirzi parameter
* Schwarzschild radius
* Spaghettification

Issues|

* Black hole complementarity
* Information paradox
* Cosmic censorship
* ER=EPR
* Final parsec problem
* Firewall (physics)
* Holographic principle
* No-hair theorem

Metrics|

* Schwarzschild (Derivation)
* Kerr
* Reissner–Nordström
* Kerr–Newman
* Hayward

Alternatives|

* Nonsingular black hole models
* Black star
* Dark star
* Dark-energy star
* Gravastar
* Magnetospheric eternally collapsing object
* Planck star
* Q star
* Fuzzball

Analogs|

* Optical black hole
* Sonic black hole

Lists|

* Black holes
* Most massive
* Nearest
* Quasars
* Microquasars

Related|

* Black Hole Initiative
* Black hole starship
* Compact star
* Exotic star
* Quark star
* Preon star
* Gamma-ray burst progenitors
* Gravity well
* Hypercompact stellar system
* Membrane paradigm
* Naked singularity
* Quasi-star
* Rossi X-ray Timing Explorer
* Timeline of black hole physics
* White hole
* Wormhole

* Category
* Commons

* v
* t
* e

Works by Roger Penrose

Books|

* The Emperor's New Mind (1989)
* Shadows of the Mind (1994)
* The Road to Reality (2004)
* Cycles of Time (2010)
* Fashion, Faith, and Fantasy in the New Physics of the Universe (2016)

Coauthored books|

* The Nature of Space and Time (with Stephen Hawking) (1996)
* The Large, the Small and the Human Mind (with Abner Shimony, Nancy Cartwright and Stephen Hawking) (1997)
* White Mars or, The Mind Set Free (with Brian W. Aldiss) (1999)

Academic works|

* Techniques of Differential Topology in Relativity (1972)
* Spinors and Space-Time: Volume 1, Two-Spinor Calculus and Relativistic Fields (with Wolfgang Rindler) (1987)
* Spinors and Space-Time: Volume 2, Spinor and Twistor Methods in Space-Time Geometry (with Wolfgang Rindler) (1988)

0.00

(0 votes)

Original source: https://en.wikipedia.org/wiki/Penrose process. Read more

|

Retrieved from "https://handwiki.org/wiki/index.php?title=Astronomy:Penrose_process&oldid=4231433"
*[v]: View this template
*[t]: Discuss this template
*[e]: Edit this template