Editing Black hole

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{{redirect|Frozen star|the hypothetical object|Frozen star (hypothetical star)}}
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{{short description|Astrophysical object from which nothing can escape}}
{{Use dmy dates|date=April 2019}}
[[File:Black hole - Messier 87 crop max res.jpg|thumb|260px|alt=Blackness of space with black marked as center of donut of orange and red gases|The [[supermassive black hole]] at the core of [[Type-cD galaxy|supergiant]] [[elliptical galaxy]] [[Messier 87]], with a mass ~7 billion times the Sun's,<ref>{{cite journal |author=Oldham, L. J. |author2=Auger, M. W. |title=Galaxy structure from multiple tracers – II. M87 from parsec to megaparsec scales |date=March 2016 |journal=Monthly Notices of the Royal Astronomical Society |volume=457 |issue=1 |pages=421–439 |doi=10.1093/mnras/stv2982 |arxiv=1601.01323 |bibcode=2016MNRAS.457..421O}}
</ref> as depicted in the first image released by the [[Event Horizon Telescope]] (10 April 2019).<ref name="NYT-20190410">{{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |title=Black Hole Picture Revealed for the First Time – Astronomers at last have captured an image of the darkest entities in the cosmos – Comments |url=http://www.nytimes.com/2019/04/10/science/black-hole-picture.html?comments#permid=31473598 |date=10 April 2019 |work=[[The New York Times]] |accessdate=10 April 2019}}</ref><ref name="APJL-20190410">{{cite journal |first1=The |last1=Event Horizon Telescope |authorlink1=Event Horizon Telescope |title=First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole |doi=10.3847/2041-8213/ab0ec7 |date=2019 |journal=[[The Astrophysical Journal]] |volume=87 |number=1}}</ref><ref name="NASA-20190410">{{cite news |last=Landau |first=Elizabeth |title=Black Hole Image Makes History |url=https://www.jpl.nasa.gov/news/news.php?feature=7372 |date=10 April 2019 |work=[[NASA]] |accessdate=10 April 2019}}</ref><ref name="bbc">{{cite web |author=Anon |year=2019 |url=https://www.bbc.com/news/science-environment-47891902 |title=The woman behind first black hole image |date=11 April 2019 |website=bbc.co.uk |publisher=[[BBC News]]}}</ref> Visible are the crescent-shaped emission ring and central shadow, which are gravitationally magnified views of the black hole's photon ring and the photon capture zone of its [[event horizon]]. The crescent shape arises from the black hole's [[#Physical properties|rotation]] and [[relativistic beaming]]; the shadow is about 2.6 times the diameter of the event horizon.<ref name="APJL-20190410" />]]
{{General relativity sidebar |phenomena}}

A '''black hole''' is a region of [[spacetime]] exhibiting such strong [[gravitation]]al effects that nothing—not even [[particle]]s and [[electromagnetic radiation]] such as [[light]]—can escape from inside it.<ref>{{harvnb|Wald|1984|pp=299–300}}</ref> The theory of [[general relativity]] predicts that a sufficiently compact [[mass]] can deform [[spacetime]] to form a black hole.<ref name="wald 1997">{{cite book |last=Wald |first=R. M. |author-link=Robert Wald |title=Black Holes, Gravitational Radiation and the Universe |editor1=Iyer, B. R. |editor2=Bhawal, B. |chapter=Gravitational Collapse and Cosmic Censorship |arxiv=gr-qc/9710068 |date=1997 |pages=69–86 |publisher=Springer |doi=10.1007/978-94-017-0934-7 |isbn=978-9401709347}}</ref><ref name="NYT-20150608">{{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |title=Black Hole Hunters |url=https://www.nytimes.com/2015/06/09/science/black-hole-event-horizon-telescope.html |date=8 June 2015 |work=[[NASA]] |accessdate=8 June 2015 |deadurl=no |archiveurl=https://web.archive.org/web/20150609023631/http://www.nytimes.com/2015/06/09/science/black-hole-event-horizon-telescope.html |archivedate=9 June 2015}}</ref> The boundary of the region from which no escape is possible is called the [[event horizon]]. Although the event horizon has an enormous effect on the fate and circumstances of an object crossing it, no locally detectable features appear to be observed.<ref>{{cite web |url=https://www.socratease.in/chapters/intro-to-black-holes-1 |title=Introduction to Black Holes |access-date=26 September 2017}}</ref> In many ways, a black hole acts like an ideal [[black body]], as it reflects no light.<ref>{{cite book |title=Gravity from the ground up |edition= |first1=Bernard F. |last1=Schutz |authorlink1=Bernard F. Schutz |publisher=Cambridge University Press |date=2003 |isbn=978-0-521-45506-0 |page=110 |url=https://books.google.com/books?id=P_T0xxhDcsIC |deadurl=no |archiveurl=https://web.archive.org/web/20161202222711/https://books.google.com/books?id=P_T0xxhDcsIC |archivedate=2 December 2016}}</ref><ref>{{cite journal |last=Davies |first=P. C. W. |authorlink1=Paul Davies |title=Thermodynamics of Black Holes |url=http://cosmos.asu.edu/publications/papers/ThermodynamicTheoryofBlackHoles%2034.pdf |journal=[[Reports on Progress in Physics]] |volume=41 |date=1978 |issue=8 |pages=1313–1355 |doi=10.1088/0034-4885/41/8/004 |bibcode=1978RPPh...41.1313D |ref=harv |deadurl=yes |archiveurl=https://web.archive.org/web/20130510184530/http://cosmos.asu.edu/publications/papers/ThermodynamicTheoryofBlackHoles%2034.pdf |archivedate=10 May 2013 |df=}}</ref> Moreover, [[quantum field theory in curved spacetime]] predicts that event horizons emit [[Hawking radiation]], with [[thermal radiation|the same spectrum]] as a [[Black-body radiation|black body]] of a temperature inversely proportional to its mass. This temperature is on the order of billionths of a kelvin for [[stellar black hole|black holes of stellar mass]], making it essentially impossible to observe.

Objects whose [[gravitational field]]s are too strong for light to escape were first considered in the 18th century by [[John Michell]] and [[Pierre-Simon Laplace]].<ref name=origin/> The first modern solution of general relativity that would characterize a black hole was found by [[Karl Schwarzschild]] in 1916, although its interpretation as a region of space from which nothing can escape was first published by [[David Finkelstein]] in 1958. Black holes were long considered a mathematical curiosity; it was during the 1960s that theoretical work showed they were a generic prediction of general relativity. The discovery of [[neutron star]]s by [[Jocelyn Bell Burnell]] in 1967 sparked interest in [[gravitational collapse|gravitationally collapsed]] compact objects as a possible astrophysical reality.

Black holes of stellar mass are expected to form when very massive stars collapse at the end of their life cycle. After a black hole has formed, it can continue to grow by absorbing mass from its surroundings. By absorbing other stars and merging with other black holes, [[supermassive black hole]]s of millions of [[solar mass]]es ({{Solar mass|link=y}}) may form. There is general consensus that supermassive black holes exist in the centers of most [[galaxy|galaxies]].

Despite its invisible interior, the presence of a black hole can be inferred through its interaction with other [[matter]] and with [[electromagnetic radiation]] such as visible light. Matter that falls onto a black hole can form an external [[accretion disk]] heated by friction, forming some of the [[Quasar|brightest objects in the universe]]. If there are other stars orbiting a black hole, their orbits can be used to determine the black hole's mass and location. Such observations can be used to exclude possible alternatives such as neutron stars. In this way, astronomers have identified numerous stellar black hole candidates in [[binary star|binary systems]], and established that the radio source known as [[Sagittarius A*]], at the core of the [[Milky Way]] galaxy, contains a supermassive black hole of about 4.3 million [[solar mass]]es.

On 11 February 2016, the [[LIGO]] collaboration [[first observation of gravitational waves|announced the first direct detection]] of [[gravitational wave]]s, which also represented the first observation of a black hole merger.<ref name="PRL-20160211" /> {{as of|2018|December|}}, eleven [[List of gravitational wave observations|gravitational wave events]] have been observed that originated from ten merging black holes (along with one binary [[neutron star merger]]).<ref name=2018Dec>{{cite web |url=https://www.forbes.com/sites/startswithabang/2018/12/04/five-surprising-truths-about-black-holes-from-ligo/ |title=Five Surprising Truths About Black Holes From LIGO |first=Ethan |last=Siegel |website=Forbes |accessdate=12 April 2019}}</ref><ref name="ligo list">{{cite web |title=Detection of gravitational waves |url=https://www.ligo.org/detections.php |publisher=[[LIGO]] |accessdate=9 April 2018}}</ref> On 10 April 2019, the first ever direct image of a black hole and its vicinity was published, following observations made by the [[Event Horizon Telescope]] in 2017 of the [[Supermassive black hole|supermassive]] black hole in [[Messier 87]]'s [[Galactic Center|galactic centre]].<ref name="APJL-20190410"/><ref name="BoumanJohnson2016">{{cite journal |last1=Bouman |first1=Katherine L. |authorlink1=Katie Bouman |last2=Johnson |first2=Michael D. |last3=Zoran |first3=Daniel |last4=Fish |first4=Vincent L. |last5=Doeleman |first5=Sheperd S. |last6=Freeman |first6=William T. |title=Computational Imaging for VLBI Image Reconstruction |year=2016 |pages=913–922 |doi=10.1109/CVPR.2016.105 |url=https://dspace.mit.edu/handle/1721.1/103077 |hdl=1721.1/103077 |arxiv=1512.01413}}</ref><ref name="NYT-20190412">{{cite news |last=Gardiner |first=Aidan |title=When a Black Hole Finally Reveals Itself, It Helps to Have Our Very Own Cosmic Reporter - Astronomers announced Wednesday that they had captured the first image of a black hole. The Times’s Dennis Overbye answers readers’ questions.|url=https://www.nytimes.com/2019/04/12/reader-center/black-holes-dennis-overbye.html |date=12 April 2018 |work=[[The New York Times]] |accessdate=15 April 2019 }}</ref>

[[File:BlackHole Lensing.gif|thumb|alt=Schwarzschild black hole|Simulation of [[gravitational lens]]ing by a black hole, which distorts the image of a [[galaxy]] in the background]]
[[File:Images of gas cloud being ripped apart by the black hole at the centre of the Milky Way ESO.jpg|thumb|Gas cloud being ripped apart by black hole at the centre of the [[Milky Way]] (observations from 2006, 2010 and 2013 are shown in blue, green and red, respectively).<ref>{{cite news |title=Ripped Apart by a Black Hole |url=http://www.eso.org/public/news/eso1332/ |accessdate=19 July 2013 |newspaper=ESO Press Release |deadurl=no |archiveurl=https://web.archive.org/web/20130721014626/http://www.eso.org/public/news/eso1332/ |archivedate=21 July 2013}}</ref>]]
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== See also ==

* [[Albert Einstein]]
* [[John Archibald Wheeler]]
* [[Stephen Hawking]]
* [[Worm hole]]
* [[Bermuda triangle]]