Talk:Black hole/Archive 15

finally added Planck star

See "Planck star" section in talk archive. I came here via that redirect 4 months after the talk mention, and was also confused that the redirected topic didn't appear in the article. Suggested language was written out in the talk section but not added. So i slightly modified it (not content, just rhetoric) and stuck it in. Someone with more knowledge is welcome to add/integrate further. "alyosha" (talk) 18:36, 23 June 2014 (UTC)

The paper has only about six cites, but I admit it's getting some coverage in the media: [1] [2]. If it were up to me I'd wait for it to get more discussion in the peer-reviewed literature, but I don't feel strongly one way or the other. Rolf H Nelson (talk) 03:56, 9 July 2014 (UTC)

I think it belongs, based on just one cite and one media mention, assuming its a positive cite and mention, per WP:NotPaper. --SmokeyJoe (talk) 04:23, 9 July 2014 (UTC)

Note that I reverted this addition a while back. Compare to a ton of stuff that we don't have space to discuss in this article, this is an incredibly obscure idea. If it is to be mentioned at all the "alternatives" section would be the place (not the "physical properties" section among (theoretically) well-established (i.e. present in most textbook statements). However, as it stands the "alternatives" section restricts attention to ideas that are notable enough to have their own article. I fear including all alternative ideas that have ever been proposed in a paper-and-a-half would fill much more than a single subsection. It might be a good idea to start a new article Black hole alternatives that gives an overview of this plethora of ideas. That would also be a much better target to redirect Planck star to.TR 08:57, 9 July 2014 (UTC)

Actually such an article already exists: Exotic star. I have redirected planck star there.TR 09:01, 9 July 2014 (UTC)

Lede continues to be confusingly vague - or plain wrong

There is no contorversy that a black hole is (when the term is used precisely, in a technical sense) the region of space (or, more correctly, space-time) which is bounded by the event horizon. Stating that the event horizon is "around" the black hole is just sloppy and will undoubtedly confuse readers. There also should be clarification between the black hole and (potentially) the singularity at its center. We do NOT know if such things (singularities) exist; other super dense states of mass/energy are possible alternatives. The term "black hole" is used both by lay and by scientific speakers to mean both the volume inside the event horizon OR the (theoretical) object at its center. IMHO, the lede needs a complete rewrite. "Around a black hole, there is a mathematically defined surface ..." Why on Earth is this a good explanation of the BORDER? There is nothing (at least not necessarily) "mathematical" about it, except that the boundary exists "in space" without any discontinuity. Why not: "The event horizon is the spherical (or ellipsoidal) border surrounding the black hole, it is a mathematically defined surface ..."
"The hole is called "black" because it absorbs..." REALLY??! Its a "hole" ?? RUBBISH! We all know the origin of the derisive term "black hole". It is called "black hole" (not "black" hole ) because 1) no light (of any wavelength) can be emitted by it and 2) because anything going 'through' it falls out of contact with the rest of the Universe.
"...all the light that hits the horizon, reflecting nothing, just like a perfect black body in thermodynamics." (same sentence). Light, as well as ANYTHING else, doesn't "HIT" the horizon! That is, nothing has yet. Light (and everything else), from the perspective of an outside observer, "gathers" AT the horizon, becoming more red-shifted (or apparently slowing down) until AT the horizon its movement STOPS. (While from the perspective of an observer traveling towards the singularity, (assuming tidal forces are surviveable), the rest of the Universe appears to be speeding up (and blue shifting) but nothing discernable 'happens' as s/he passes through the horizon, its a "non-event". These are two valid descriptions, the POV of an observer outside, or of the traveling observer. There are also two invalid descriptions: from the "POV" of light (light experiences no time, ever. Hence has no POV.) or from the POV of an observer "inside" the event horizon. Obviously, light "hitting" the horizon is NOT "just like" [hitting] a perfect black body in thermodynamics! I assume "ideal", not "perfect" is meant, but what "in thermodynamics" means, is anyone's guess. (I presume it means the mathematical treatment of the thermodynamics of black body radiation.)
"Quantum field theory... predicts that event horizons emit radiation like a black body..." Here we go again! How is this helpful to the 99% of readers who have no idea what "like a black body" means?? Am I the only one who thinks that the claim that no light escapes the horizon and the claim that the horizon emits radiation are CONTRADICTIONS? Isn't it true that QFT predicts emission from ABOVE the (mathematical surface of the) horizon?? (Granted, not very far above.) Why isn't this described as the evaporation of the black hole? My understanding of the facts are: 1. Black Holes are believed to exist based on many indirect lines of evidence, but have never been (can never be) directly observed. We do not understand the physics inside of black holes. 2. Black holes may (theoretically) exist in all sizes, but they radiate their mass away at a rate inversely proportional to their radius. Hence the lifetime of small black holes is short, none exist for long; while larger ones, stellar sized or larger, have lifetimes of billions of years. 3. The shape of the event horizon is spherical in the ideal case of one without spin. We believe black holes will have significant spin, and hence their event horizons will be ellipsoidally distorted. 4. Black holes have no hair. 5. All black holes are believed to be surrounded by accretion disks: matter, caught in the gravitational pull of the b.h., spiralling into it. Collisions between objects in the accretion disk heats the disk to extreme temperatures. A lot of light is emitted by these disks, so that the idea that black holes exist "in the dark" isn't correct. 6. It is believed that virtually all galaxies have a central black hole.Abitslow (talk) 15:30, 10 July 2014 (UTC)

Quick reply (I'll get back to rest later when I have more time). Your point 5 is false. Not all black holes are expected to have accretion disks. Accretion disks only occur if there is a source of matter to accrete (like a stellar companion losing gas). There should be a large population of accretion diskless black holes. However, these will be very hard to find.TR 16:40, 10 July 2014 (UTC)

Please dial the tone down a few notches, this style is not exactly conducive to a constructive discussion of the problems you see with the article.

I edited the lead, is this better? Paradoctor (talk) 19:36, 10 July 2014 (UTC)

• I agree with much of the sentiment of Abitslow. "The term "black hole" is used both by lay and by scientific speakers to mean both the volume inside the event horizon OR the (theoretical) object at its center" for example, is my understanding, and reading the lede didn't help. --SmokeyJoe (talk) 05:01, 14 July 2014 (UTC)

First thing I hear. If this is widespread usage, surely there are sources in support of this claim? Paradoctor (talk) 09:01, 14 July 2014 (UTC)

What I think I gathered, from the article reflecting scholarly usage, is that the "black hole" is the volume inside the event horizon (as defined/conjectured not observed). I guess that the concept of the thing inside, the singularity of infinite density or something bigger, like the planck star, these hypothetical, or more tenuously conjectured things are best described at exotic star? --SmokeyJoe (talk) 09:18, 14 July 2014 (UTC)

In scholarly usage the term "black hole" always refers to a spacetime geometry that has an event horizon (+ some compactness condition to exclude geometries with a cosmic horizon. Nobody (in the Scholarly literature) refers to the singularity at the centre as a "black hole". (In fact, in a strict sense this not even a part of geometries called "black holes" since GR is not well-defined at the singularity.)TR 09:39, 14 July 2014 (UTC)

Some comments about the OP's comments:

• About the phrasing "mathematical surface". I believe that however inserted that phrasing was trying to emphasize that the event horizon is not a physical surface. The presence of an event horizon follows from the global properties of a space time, and cannot (in a strict sense) be inferred from just local observations. I have rephrased this a bit more explicitly.
• About "hitting the horizon". Whether an object can hit the horizon or not depends on your notion of "now". Saying that for outside observer objects never hit the black hole implies that "now" is the boundary of the causal past of the observer. That also implies that the CMB currently being observed was emitted "now" (which is a rather non-standard idea of now). It is to produce timeslicings in which objects hit the horizon in "finite time". (It remains true that an outside observer never sees on object hit the horizon, but that is because the light will take an infinite time to reach the observer).
• " Am I the only one who thinks that the claim that no light escapes the horizon and the claim that the horizon emits radiation are CONTRADICTIONS? Isn't it true that QFT predicts emission from ABOVE the (mathematical surface of the) horizon?? (Granted, not very far above.)"

First note that the lede never said nothing can escape the event horizon. Instead it said that nothing can escape from inside the event horizon. (A subtle, but relevant distinction). This is not a contradiction with the event horizon emitting radiation, it rather is a paradox. (Not unrelated to the black hole information paradox). The mathematics of Hawking radiation is rather subtle. In the end it has to do with the fact that there is no universal definitions of particle and vacuum. One way of think of it though is as the event horizon emitting radiation both inward and outward, with the inward radiation having negative energy. I believe the simplest way of phrasing this in the lede, is as the event horizon emitting radiation. (The presence of the event horizon is essential to the existence of the Hawking radiation.TR 10:28, 14 July 2014 (UTC)

"is defined as"

The current first line uses the awkward phrasing "is defined as". In my opinion this is completely superfluous (and contrary to normal style conventions on Wikipedia). When an article begins with a sentence of the form "An A is an B with property C." It is clearly implied that this is a (sketch of a) definition. There is no need for further emphasis of this.

Moreover, this phrasing wrongly suggests that this is the exact definition of black hole. (Rather than a paraphrasing avoiding technical language.)TR 09:53, 14 July 2014 (UTC)

SmokeyJoe inserted the phrase, and I don't understand the edit summary. I was meh, but now that you pointed out the implication, I support removing it. Paradoctor (talk) 10:04, 14 July 2014 (UTC)

• I see your point, and undid my revert of its removal. Note that Timothy put it in first, "incorporate good suggestion from talk page".

The problem with the current version of the lede is that it reads as assuming that black holes exist, without question, whereas they are largely mathematical, inferred from indirect evidence, and certainly not directly observed. This is about a subtle distinction, not questioning the concept. So "defined as" doesn't work so well. It is not easy to suggest something better, but I do think that a rewrite of the lede could help. The word "concept" or "model" or "theory" could be worked in, but simple attempts to do this swing the problem too far to the other side. Perhaps "well accepted theory"? Perhaps mention the history? Perhaps "A black hole is a region of spacetime, predicted by the theory of general relativity, from which gravity prevents anything, including light, from escaping.[1]" --SmokeyJoe (talk) 11:03, 14 July 2014 (UTC)

"Timothy put it in first"

"black holes exist" I think what you mean is "have been observed". Saying that "black holes are x" implies "x exist" no more than saying "Dumbo is a flying elephant" implies "flying elephants exist". It's a non-technical definition, no more. Paradoctor (talk) 11:48, 14 July 2014 (UTC)

I change my mind from time to time. Agree with the Dumbo example. Note also that the current second sentence already reads (paraphrasing): "GR predicts that black holes should exist". The problem with the sentence that SmokeyJoe suggests ("A black hole is a region of spacetime, predicted by the theory of general relativity, from which gravity prevents anything, including light, from escaping.[1]") is that the definition of black hole does not depend on general relativity. "Does gravity theory X predict black holes?" is a valid question. (And one that is frequently asked of alternative theories X in research).

If after the first two sentenced a reader is still in doubt about the existential status of black holes after the first two sentences, this is clarified further in the discussion of the history in the second paragraph, and the discussion of the observational status in the fourth.TR 13:04, 14 July 2014 (UTC)

Size

Normaly you think about the stellar and the supermassive, but there is more black than you imagine. To find better or even think about to look for the different sizes , I made this proposal: [3]. It wasn´t liked. Perhaps this one:

Overview tables

So you can see it in the contents-box. Best at the first position before history or at least at the bottom? --Palitzsch250 (talk) 17:01, 24 September 2014 (UTC)

Please look at the bottom of the article, where these navboxes are already included. See WP:NAVBOX. Paradoctor (talk) 19:02, 24 September 2014 (UTC)

Please note that there already is a table of blackhole sizes in the "physcial properties" section.TR 11:02, 25 September 2014 (UTC)

Thanks, but I saw both. ″So you can see it in the contents-box.″ --Palitzsch250 (talk) 13:46, 25 September 2014 (UTC)

You are aware that we can't change the content of the "Contents" box? Paradoctor (talk) 16:37, 25 September 2014 (UTC)

Missing commata

3rd paragraph, 2nd sentence: "After a black hole has formed [comma missing] it can continue to grow by absorbing mass from its surroundings." 149.172.54.252 23:20, 2014 October 18

 Done Thanks, Paradoctor (talk) 01:52, 19 October 2014 (UTC)

New NEWS today, for future editing

A lot of news about Black Hole discovery possibilities.

Headline-1: Black hole at Milky Way center may be emitting mysterious neutrinos, NASA says

• http://rt.com/news/205803-nasa-black-hole-neutrinos/

QUOTE: "The massive black hole at the heart of our milky galaxy may be churning out peculiar particles called neutrinos, NASA satellites have revealed. If verified, it would be the first time neutrinos have been traced to the darkest regions of spacetime. The subatomic activity was first detected by three NASA satellites, which observe in x-ray light: the Chandra X-ray Observatory, the Swift gamma-ray mission, and the Nuclear Spectroscopic Telescope Array (NuSTAR), [NASA said in a press announcement]." -- AstroU (talk) 02:28, 17 November 2014 (UTC) -- PS: FYI for future editing.

Headline-2: NASA X-ray Telescopes Find Black Hole May Be a Neutrino Factory

• http://www.nasa.gov/centers/marshall/news/news/releases/2014/14-169.html#.VGldofnF-Sr

QUOTE: "The giant black hole at the center of the Milky Way may be producing mysterious particles called neutrinos. If confirmed, this would be the first time that scientists have traced neutrinos back to a black hole. The evidence for this came from three NASA satellites that observe in X-ray light: the Chandra X-ray Observatory, the Swift gamma-ray mission, and the Nuclear Spectroscopic Telescope Array (NuSTAR)." -- AstroU (talk) 02:31, 17 November 2014 (UTC) -- PS: FYI for additional future editing.

These two are obviously about the same thing. Some comments:

1. This one paper, that needs further corroboration before the proposed hypothesis should be included here. (ie. WP:TOOSOON.
2. The neutrino's are at best traced to the vicinity of Sgr A*. (Given IceCubes angular resolution).
3. Given that the temporal coincidence is with X-ray flares, the actual source of the neutrino's is more likely to be the accretion disc, not the black hole itself. (somewhat of a duh).
4. More natural places to include a reference to this would be Sgr A*, accretion disc, or supermassive black hole.TR 14:03, 17 November 2014 (UTC)

Headline-3: NASA finds ‘monster’ black hole in tiny galaxy

• http://rt.com/news/188864-nasa-monster-black-hole/

QUOTE: "... But what really surprised astronomers is the supermassive black hole they found inside M60-UCD1. Lurking in the smallest galaxy, the black hole is five times the mass of the one at the center of our Milky Way galaxy. It has a mass equal to 21 million suns, and is 15 percent of the small galaxy's total mass – but less than 0.01 percent of the Milky Way’s total mass." -- AstroU (talk) 02:35, 17 November 2014 (UTC) -- PS: FYI for additional future editing.

Again more natural content for supermassive black hole (which includes an overview detection candidates).TR 14:05, 17 November 2014 (UTC)

Article expansion

This article should expand to emphasize that there is a wider range of aspects involved around description of what properties black holes poses - because definition of black hole in astronomy differs from definitions and proposed properties of black holes for purposes of mathematics, metaphysics, science-fiction (and pseudo-science in general) and psychology for example.— Preceding unsigned comment added by 109.93.211.157 (talk • contribs) 21:18, July 10, 2013 (UTC)

Done? -- AstroU (talk) 02:22, 17 November 2014 (UTC)

No, because 1) I cant make grammatical sense of the comment. 2) The part that I am able to parse is untrue. (Black holes in astronomy and mathematics have exactly the same properties (for as far as we know anyway.) TR 14:09, 17 November 2014 (UTC)

Introduction article

An editor over at Wikipedia:Village pump (idea lab)/Archive 16#Making wikipedia more accessible suggested creating introduction articles, which we already have of course, but this editor specifically mention this article as one that could use one. Oiyarbepsy (talk) 15:43, 9 December 2014 (UTC)

Go make a black hole article on the Simple English Wikipedia. Weegeerunner (talk) 19:49, 11 December 2014 (UTC)

That's not the same thing. Introduction to special relativity is here at standard English wiki. It's about having less technical information and math to be more accessible to those without an understanding of physics. Oiyarbepsy (talk) 20:51, 11 December 2014 (UTC)

Simple English Wikipedia is for people who struggle with English, not people who struggle with advanced physics. I actually really like the original suggestion of having more introduction articles on Wikipedia, the only problem now is finding someone who will write one. Bzweebl (talk • contribs) 02:16, 12 December 2014 (UTC)

How long does it take a typical black hole to dissipate?

How long does it take a typical black hole to dissipate? This seems like it would interesting information, but it's not in the article. Abyssal (talk) 14:09, 2 February 2015 (UTC)

It's in there, but it's not a simple answer. Most black holes in our universe will required 10 to the 50th years or something, because they keep sucking more mass in than they are Hawking out. Oiyarbepsy (talk) 15:23, 2 February 2015 (UTC)

Lol, Hawking out Tetra quark ^(talk) 15:33, 2 February 2015 (UTC)

Powerful winds in Black holes

A great chance for astronomers to understand the formation of the galaxies and measuring the strength and speed of these winds and answer unsolved questions. As we may know quasar winds can contribute to mass loss in a galaxy. for more information please refer to this website:

http://phys.org/news/2015-02-telescopes-furious-black-hole.html — Preceding unsigned comment added by Mjesfahani (talk • contribs) 07:42, 21 February 2015 (UTC)

Gravitational Collapse

Under this topic, they need to expand on the fact that High Mass Stars can collapse on itself, because they only say that "stars" collapse on its own gravity but low mass stars will not be able to make a black hole. Ashishg96 (talk) 18:43, 9 February 2015 (UTC) MansourJE (talk) 07:56, 21 February 2015 (UTC)

black hole

sun spots are black, light cannot escape, are black holes massive stars or objects with gravity so strong no light can be seen. — Preceding unsigned comment added by 86.187.140.145 (talk) 15:12, 23 February 2015 (UTC)

Sunspots are not black and definitely not black holes. It's best not to think of black holes as stars or any other familiar object. They are dense collections of highly compressed matter which can come from any source. Just put any matter into a small enough space and you will have created one. Cutelyaware (talk) 12:18, 28 February 2015 (UTC)

Semi-protected edit request on 12 March 2015

This page has been vandalized. It starts with , "A black hole is a a masive fani that bliws up and destroys the universe of spacetime" It should be reverted back to the previous edit, "A black hole is a mathematically defined region of spacetime" Ardujustin (talk) 08:51, 12 March 2015 (UTC)

 Done - by another - thanks for pointing that out - Arjayay (talk) 09:19, 12 March 2015 (UTC)

Semi-protected edit request on 21 March 2015

I like insert a link to the embedding of the Schwarzschild solution.

https://www.google.de/search?q=(5*8*((x%5E2%2By%5E2)%5E0.5-2*8))%5E0.5%2C+x+is+from+-100+to+100%2C+y+is+from+-100+to+100%2C+z+is+from+0+to+-100&oq=(5*8*((x%5E2%2By%5E2)%5E0.5-2*8))%5E0.5%2C+x+is+from+-100+to+100%2C+y+is+from+-100+to+100%2C+z+is+from+0+to+-100&aqs=chrome..69i57.808j0j7&sourceid=chrome&es_sm=93&ie=UTF-8#safe=off&q=(5*8*((x%5E2%2By%5E2)%5E0.5-2*8))%5E0.5%2C+x+is+from+-100+to+100%2C+y+is+from+-100+to+100%2C+z+is+from+0+to+100

Schwarzschild, Karl. "Über das gravitationsfeld eines massenpunktes nach der einsteinschen theorie." Sitzungsberichte der Königlich Preußischen Akademie der Wissenschaften (Berlin), 1916, Seite 189-196 1 (1916): 189-196. MoocSummers (talk) 22:59, 21 March 2015 (UTC)

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. --I am k6ka ^{Talk to me!} _{See what I have done} 02:01, 22 March 2015 (UTC)

Semi-protected edit request on 5 April 2015

In the fourth paragraph it says "with electromagnetic radiation such as light.", 'light' should be changed to 'visible light'. --DeltaStrangeCharm (talk) 22:30, 5 April 2015 (UTC)

Done Kharkiv07^Talk 22:40, 5 April 2015 (UTC)

Growth of Black holes

To the authors, 4 articles which may be of possible interest regarding the growth of Black holes. http://www.nature.com/news/3d-simulations-of-colliding-black-holes-hailed-as-most-realistic-yet-1.17360 (added in the Video section)

http://journals.aps.org/prd/abstract/10.1103/PhysRevD.90.104030 Accretion disks around binary black holes of unequal mass: General relativistic MHD simulations of postdecoupling and merger

http://iopscience.iop.org/2041-8205/803/2/L16/ A PERIODICALLY VARYING LUMINOUS QUASAR AT z = 2 FROM THE PAN-STARRS1 MEDIUM DEEP SURVEY: A CANDIDATE SUPERMASSIVE BLACK HOLE BINARY IN THE GRAVITATIONAL WAVE-DRIVEN REGIME

http://www.nature.com/nature/journal/v518/n7537/pdf/nature14143.pdf A possible close supermassive black-hole binary in a quasar with optical periodicity Jcardazzi (talk) 00:26, 21 April 2015 (UTC)jcardazzi

Discussion about the formation of the black hole

me ever before listen or studied about black hole that the cause of its origin is just a vast big bang over the universe is it true ? this known that a millions of yeras ago there occured a big bang over the universe and after it the mass ball was crushed into peaces and then after all pieces were divided into the universe is it True ? — Preceding unsigned comment added by 125.19.97.82 (talk) 04:09, 30 May 2015 (UTC)

Can we reach another dimension through a blackhole?

Post removed - user promoting his own website Theblackstack (talk) 03:13, 17 July 2015 (UTC)

Discussion about protecting this page on another discussion page

See User talk:Oiyarbepsy/2015F#Protection request response Oiyarbepsy (talk) 04:24, 2 August 2015 (UTC)

Semi-protected edit request on 17 October 2015

Please change first line of the article from "such as light—can escape from inside it." to "such as light—can't escape from inside it." I think we its clear from the very definition of black hole. 2601:600:8200:4160:D15E:5815:22DB:7F36 (talk) 22:49, 17 October 2015 (UTC)

 Not done Welcome to Wikipedia. Your quote is missing some context: "nothing—including particles and electromagnetic radiation such as light—can escape from inside it". I bolded the relevant part. Paradoctor (talk) 23:13, 17 October 2015 (UTC)

Mistake on diagram

The diagram labelled "A simple illustration of a non-spinning black hole" has the wrong formula for the Schwarzschild radius. Andrewthomas10 (talk) 21:52, 24 November 2015 (UTC)

"The singular region can thus be thought of as having infinite density."

Is that sentence actually accurate?  I mean, I would think that if we're taking a positive, real mass and dividing it by zero volume, the result would be undefined density, not infinite density.  No?  allixpeeke (talk) 06:29, 5 August 2015 (UTC)

Why would you think that? Division of a finite number by zero normally gives (complex) infinity (in some sense).

However, the sentence is purposefully hedged ("can be thought of"). Because the singularity is singular, most statements that you would try to make about it are ill-defined in some way. Technicalities not withstanding, conceptually is useful to think of the singularity as have infinite density.TR 08:23, 5 August 2015 (UTC)

Conceptually useful, I'll grant; but technically accurate?  If one wishes to include conceptually-useful statements alongside technically accurate ones, that's fine; I just worry we might be providing a conceptually-useful statement in place of a technically-accurate one.  allixpeeke (talk) 19:12, 5 September 2015 (UTC)

It is a singularity, so there are no technically-accurate statements to make. That being said the statement: 1) the singularity has finite mass. 2) the singularity has zero volume are as close to technically accurate as you can get. Once you accept those two statements, the statement that its density is infinity follows directly.TR 23:18, 5 September 2015 (UTC)

You write, "the statement that its density is infinity follows directly."  This is what I believe is not technically accurate.  While it might be conceptually useful to think of x/0 as ∞, it is not technically accurate to say that x/0 = ∞.  Technically, x/0 = "undefined."  See undefined (mathematics).  See also division by zero.

No, that is an oversimplified arithmetic analysis. The limit of the density as the volume approaches zero is positive infinity: $\lim _{b\to 0^{+}}{a \over b}=+\infty$. As TimothyRias notes, it is a singularity - essentially a gap in our current understanding of physics. VQuakr (talk) 07:36, 7 September 2015 (UTC)

(ec)As you can read in division by zero there are plenty of ways to make the statement "a/0+ = infinity" meaningful. Probably, the easiest way is by looking at the negation: "Suppose the density of the singularity is finite, then since it has zero volume it must have zero mass. Consequently, since we know the mass of the singularity to be non-zero, we conclude that the density must ∞ (assuming that density must take a value in the interval [0,∞])." The formal undefinedness of division by zero in arithmetic is related to problems with defining 0/0. For non-zero a however, the statement a/0=ComplexInfinity is meaningful. This is why most computer algebra programs will give exactly that answer. [4] TR 07:39, 7 September 2015 (UTC)

General relativity treats if it were infinitely dense. --Monochrome_Monitor 10:23, 28 November 2015 (UTC)

Now, under some models it's just VERY VERY VERY dense, and others it's a portal to another universe. --Monochrome_Monitor 10:24, 28 November 2015 (UTC)

GA Article?

This article is awesome. Thorough, professional, comprehensive. I'm not sure why it got downgraded to GA. What could make it a featured article? --Monochrome_Monitor 04:23, 28 November 2015 (UTC)

I'm wondering because it's the most viewed article of astronomy by far, so it's pretty damn important to the project. --Monochrome_Monitor 10:16, 28 November 2015 (UTC)

It got downgraded to B (maybe even C) class at some point because it was in a dire state. Over the years I (and others) have spent quite some energy into getting it to its present state. (Hence I much appreciate your compliment.) I currently don't have the time or energy to get it to FA state. However, if someone were to make the effort, I'd be glad to help out. I think to get there, it will need some minor updating for developments over the last 5 years or so. In particular, it should probably mention ongoing efforts of the Event Horizon telescope and GRAVITY to provide more direct observational evidence for the existence of a horizon.TR 11:11, 8 January 2016 (UTC)

New NEWS today, for future editing: ('skinny black hole')

What other news comes from the American Astronomical Society's annual meeting?

Headline-1: Rare galaxy found with 2 black holes - one starved of stars

• http://www.foxnews.com/science/2016/01/06/rare-galaxy-found-with-2-black-holes-one-starved-stars.html?intcmp=hphz07

QUOTE: "An astrophysicist has discovered something even rarer than a double-black hole galaxy: a skinny black hole. The University of Colorado at Boulder's Julie Comerford reported her findings Tuesday at the American Astronomical Society's annual meeting in Kissimmee, Florida." -- Charles Edwin Shipp (talk) 03:41, 7 January 2016 (UTC) -- PS: FYI for future editing.

This seems more relevant for the more specialized articles Intermediate mass black hole or Supermassive black hole.TR 11:15, 8 January 2016 (UTC)

Sentence detail

In the Observational Evidence section, one sentence in the third paragraph begins as follow: "It was the first ever a black hole merger;". Seems to me like this could somehow be reformulated better. --66.185.60.38 (talk) 20:03, 16 February 2016 (UTC)

Evidence that the standard black hole event horizon model is incorrect.

See the wiki article Astrophysical jet, specifically the paragraph on IGR J11014-6103. The relativistic jet from IGR J11014-6103 does not originate from an accretion disk since there is no accretion disk. Therefore this jet has to come from within the star, almost certainly from a core with a relativistic center. This is glaring evidence that the conventional model of >0.5c jets originating outside of a star is incorrect. This also implies that the conventional "black hole" model of a singularity/event-horizon is incorrect.173.68.155.15 (talk) 20:42, 10 February 2016 (UTC)BG

There are many different types of observed, astrophysical jets --- seen from protostars, neutron stars (NS), and black holes (BH). Not only are these jets different observationally, they are believed to be produced from very different mechanisms. Jets from NS without apparent accretion disks do not contradict models for BH jets, and especially not for the entire model of BHs themselves. Zhermes (talk) 20:51, 10 February 2016 (UTC)

Refer to paragraph IGR J11014-6103 at Astrophysical jet. The 0.8c jet is being ejected from the core of the pulsar; indicating this neutron star is basically a mix of conventional matter with a little bit of ultra-relativistic matter (leptons). This suggests a stellar "black hole" is basically the same thing (a finite size star) but with a higher percentage of ultra-relativistic matter.173.68.155.15 (talk) 23:24, 17 February 2016 (UTC)BG

That is a rather peculiar system to begin with (the neutron star is moving through the interstellar medium at supersonic speeds). Hence it seems hard to extrapolate any conclusions to more conventional systems. Further, I see no evidence in the literature of your assertion that this jet must emanate from the core.TR 10:02, 18 February 2016 (UTC)

Something "might" escape

It is time once again to point out the incompatibility of the definition of a black hole with Hawking radiation. According to the introduction: "nothing—including particles and electromagnetic radiation such as light—can escape from inside it".

According to the Evaporation section: "If Hawking's theory of black hole radiation is correct, then black holes are expected to shrink and evaporate over time as they lose mass by the emission of photons and other particles."

I have been stomped on for pointing this out before, but I'm sorry... it jumps out at me every time I read the article.192.249.47.204 (talk) 20:52, 1 March 2016 (UTC)

And again Hawking radiation does not 9have to) come from inside the black hole.TR 21:45, 1 March 2016 (UTC)

Yes, that was the previous explanation. However, that was before the "black holes ... shrink and evaporate over time as they lose mass by the emission of photons and other particles" was added to the article. Is there an explanation as to how this can occur without anything coming from inside?192.249.47.204 (talk) 20:25, 2 March 2016 (UTC)

It depends on your definition of "from". At very small scales, quantum effects dominate and space becomes counter-intuitive. So from a macroscopic perspective the black hole is emitting radiation and losing mass, but no particle is travelling out from within the event horizon. VQuakr (talk) 20:41, 2 March 2016 (UTC)

One particle/anti-particle pair is created near the event horizon by quantum fluctuations, one particle falls into the black hole and by quantum tunneling the other escapes the one that escapes carries the mass/energy away.Quantanew (talk) 14:43, 4 March 2016 (UTC)

section on LIGO is wrong

The masses in the LIGO section are mis-stated; there were 3 solar masses lost due to gravitational waves; this is kind-of a very central, important part of the result, so getting it wrong is ... not good. Also. The statement that there is "at least one" researcher who believes that LIGO was first to detect the event is absurd: there's a whole mass (about on-thousand) co-authors on the paper: making it sound like there's just one is goofy. 67.198.37.16 (talk) 02:08, 23 March 2016 (UTC)

Since it's causing confusion, maybe we should just drop the "the first direct detection of black holes" line. Most sources seem to characterize it as an indirect detection of two black holes and the first direct detection of a collision event. Direct vs. indirect is subjective, but it's hard for me to see a definition of "direct" that would simultaneously admit LIGO, but exclude all the previous detections of black holes. Rolf H Nelson (talk) 07:49, 23 March 2016 (UTC)

Specifically, its 29+36=62 with about 3 solar masses lost as waves. The WP article on this does get the details right. 67.198.37.16 (talk) 02:17, 23 March 2016 (UTC)

Looking at the abstract, the uncertainty bars are +/- four solar masses, so that might be unwarranted precision. IMHO the current ~30 and ~60 are fine. Rolf H Nelson (talk) 07:49, 23 March 2016 (UTC)

Hi @67.198.37.16: I'll edit the masses of the black holes accordingly. That said, I would argue that approximate masses are acceptable because the purpose of that section is to invoke the overall LIGO result as independent, compelling evidence of the existence of black holes; it doesn't purport to describe the LIGO result in detail, and it doesn't need to do so given its limited aims. As a result, some important details about the black-hole merger, such as the amount of mass converted into energy, aren't relevant within that context. (Obviously, they are critically relevant in the article dedicated to the LIGO detection, and I would not be OK with approximate masses in that article.)

Hi @Rolf H Nelson: I think that "direct" is appropriate because the LIGO measurements show that the merging objects were so massive and compact that they must have been black holes. I am not aware of a credible alternative explanation for the observed waveform. As for the phrase "In what at least one researcher has characterized as the first direct detection of black holes," it establishes at the outset why the LIGO result is being mentioned as observational evidence for black holes. Would "In what has been characterized as the first direct detection of black holes" be more acceptable? Full disclosure: I wrote that phrase, but I'll be the first to admit that it could be improved upon. Thank you both for your thoughts, and best wishes, Astro4686 (talk) 03:07, 25 March 2016 (UTC)

'I think that "direct" is appropriate because the LIGO measurements show that the merging objects were so massive and compact that they must have been black holes.' OK, but do you also believe "direct detection" is *inappropriate* for each and every of the various previous observations over the years that had already confirmed the existence of black holes? It seems to me that by your same criteria ("no other explanation for observation" -> "direct observation"), certain previous observations would also be "direct", in which case this isn't the *first* direct detection. Your proposal of "In what has been characterized as the first direct detection of black holes" is fine with me, but if you're asking my personal preference I would just yank the "direct observation of black holes" claim as being a minority viewpoint about a minor terminological distinction that's unimportant to most readers. Rolf H Nelson (talk) 05:54, 25 March 2016 (UTC)

Hi @Rolf H Nelson: I've decided that I agree with you about removing 'direct detection.' This conversation has underscored how subjective that term is (and also that my previous thoughts about it were hasty and ill-conceived). Indeed, if one term requires such careful definition, then it's probably best to avoid it in the article. For what it's worth, I think that the best definition of a 'direct detection' is an observation showing that a BH candidate possesses an event horizon (i.e., the defining characteristic of a BH), and with the LIGO result, a separation of 350 km for two BHs with 36 M_sun and 29 M_sun *doesn't* fulfill that description (since the minimum detected separation of 350 km is still greater than the sum of the Schwarzchild radii). I think that you hit the nail on the head when you wrote, "Most sources seem to characterize it as an indirect detection of two black holes and the first direct detection of a collision event." Best Wishes, Astro4686 (talk) 09:03, 25 March 2016 (UTC)

In a strict sense BHs cannot be observed directly by an outside observer because (by definition) a black hole exists only outside the causal past of any outside observer. However barring that technicality, the closest we are ever going to get to directly observing a BH is seeing the ringdown signal. The ringdown quite literally is the gravitational radiation emitted as the BH settles down to a stationary state. In that sense the LIGO observation is much much closer to being a direct detection of a BH than an other observation that came before it. Unfortunately, from LIGO observation it is only possible to see the dominant quasinormal mode in the ringdown (and even that is not very well constrained). The properties of the dominant QNM are pretty much determined by the presence (and geometry) of a photon sphere. Consequently, it is not quite possible to rule out various exotic alternatives that have a similar photon sphere. If for a future detection (when LIGO is running at full design sensetivity) we are able to isolate some of the overtones of the ringdown as well, then that will severely constrain the possible alternatives.TR 16:16, 25 March 2016 (UTC)

Hi @TimothyRias: Thank you for your detailed explanation. If you have a moment, perhaps you might like to edit the section to explain some of this. I'd do it myself, but I lack your expertise with gravitational waves. Best Wishes, Astro4686 (talk) 17:08, 25 March 2016 (UTC)

<<<unindent. Yes, I guess saying "approx 30 solar masses" is OK. I had the exact figures stuck in my head when I first read this, but now that they've faded away ... OK. The problem with "at least one researcher" is that most UFO sightings and paranormal phenomena involve "at least one researcher". This is much more credible than that. What makes this a "direct" sighting is that changes to the metric are directly measured, as opposed to inducing the metric from orbital precession, or gravitational lensing, M-sigma relation, etc. 67.198.37.16 (talk) 21:30, 4 April 2016 (UTC)

Delete GIF please

The GIF currently attached to the article is far too distracting. Please delete to make reading easier. — Preceding unsigned comment added by Rickmoede (talk • contribs) 18:28, 8 August 2016 (UTC)

FWIW I personally like the animated GIF at the top of the article showing gravitational lensing, assuming that's what you're talking about. Is there a replacement image being proposed, or just deletion? Rolf H Nelson (talk) 04:55, 9 August 2016 (UTC)

I do understand it to be a matter of personal taste in either instance, and I do find it distracting. While I see that it meets with WP:PERTINENCE more effectively than would a still, the problem is that Wikipedia's css doesn't allow for a maximum number of loops for animated gifs. Perhaps a good compromise would be to place it further down in the text so as the sidebar is moved up to the prominent position it should preferably have? I've gone WP:BOLD and moved it down as it does overwhelm the lead, but other editors are welcome to revert me. --Iryna Harpy (talk) 21:25, 10 August 2016 (UTC)

Split?

I don't know about anybody else, but it seems clearer to me if there was to be a clear disambiguation of astronomical black hole versus black hole solution. My recommendation would be to split this article into the above two recommendations, and link both from the disambiguation page, with some discussion about the relation between the two. At a minimum, my feeling is that the two above terms should have redirect pages to an appropriate location. — Preceding unsigned comment added by 70.247.163.128 (talk) 18:56, 13 August 2016 (UTC)

Please sign all your talk page messages with four tildes (~~~~). Thanks.

I don't think it would be a good idea to split theory and observation—on the contrary. We could however create redirect pages for both terms to this article. - DVdm (talk) 19:12, 13 August 2016 (UTC)

My feeling is that it remains very unclear in this article which context one is speaking from. Redirects to sections here would probably do a lot to make the context clearer. I'm definitely not advocating for a divorce, but the rules of inference in the astronomical realm and in the theoretical realm are completely different, and I would like to see a better exposition of both of those lines of thought, however it can be accomplished. 70.247.163.128 (talk) 20:37, 13 August 2016 (UTC)

Note also that there is sensible precedent for separating theory and observation. Best example I can think of would be electromagnetic field and magnet. 70.247.163.128 (talk) 21:15, 14 August 2016 (UTC)

This does not really make sense to me. There really is no such thing as an "astronomical black hole" in the sense that there is phenomological class of objects that are observed and dubbed "black holes". Black holes in astronomy almost always appear as a theoretical explanation for other phenomological classes of objects such as quasars or active galactic nuclei. From that perspective there really is little sense in the split you suggest, since all we know about black holes is from theory. This knowledge will either fit observations (in which case they can be explained by black holes) or it doesn't (in which the observation cannot be explained by a black hole).TR 15:34, 15 August 2016 (UTC)

Honestly, that's exactly the point. That phenomenological class is the astronomical black hole. It's informed by astronomical observation. The black hole solution, is informed by gravitational theory like General Relativity, and may ultimately be disjoint from observation. I think we agree on that. But if it turns out that current theory and observation are disjoint, it seems that you would suggest that black holes don't exist. My position would be that they exist theoretically, but not physically. This situation happens in many other theories, and while there may be a reality invalidated by observation, it doesn't invalidate the theoretical concept, except in implementation. I would again point to magnets. If it turned out that electromagnetic theory is not an accurate depiction of reality, then that in no way reduces the reality of observed physical magnets. The theoretical concept still carries weight, even if only as an effective description of the physical interactions. Moreover, I don't believe anyone would confuse a physical magnet with the idealization of a magnet that is captured by theory. I could argue that there's really no such thing as a physical magnet, it can all be reduced to the theoretical concept, but that is to gloss over a very real distinction between theory and experience which requires explanation. 70.247.163.128 (talk) 18:46, 20 August 2016 (UTC)

But there is no phenomenological class of objects known as "black holes". There is many classes of phenomenological classes of objects that feature black holes in their theoretical explanation but there currently no class of observations that we would label "black holes" (and continue to do so even if they would fail to agree with current theoretical expectations). This mainly because we do not directly observe any of the qualities that would characterize it as a black hole. This might changes with the event horizon telescope, but currently this is the state of affairs.TR 16:57, 21 August 2016 (UTC)

I see your point more clearly now, but if that's the case, then the tone of this article is way off (maybe you agree). If there's no objective astronomical definition of what constitutes a black hole, then the development of the article should be the development of the black hole solution with applications. Among the applications would be a possible explanation of astronomical phenomena, in particular, falsifiable astronomical models (astronomical black holes). Either way, though, I still see value in both black hole solution and astronomical black hole as descriptors. — Preceding unsigned comment added by 70.247.163.128 (talk) 19:26, 23 August 2016 (UTC)

If there's no objective astronomical definition of what constitutes a black hole... Huh? And no, both proposed titles seem very contrived and I do not see any good reasons proposed for a split. VQuakr (talk) 01:21, 24 August 2016 (UTC)

cut overbloated lede

Lede too bloated and turgid. History in lede should be moved to history etc.--86.187.175.218 (talk) 23:17, 26 August 2016 (UTC)

Added Archives

I will add 5 access-dates and 11 archive urls to the citations in this page. Details:

• Added access date for http://cosmos.asu.edu/publications/papers/ThermodynamicTheoryofBlackHoles%2034.pdf, (see diff when it was first added to article); Added archive url too
• Added access date for http://www.phys.uu.nl/~thooft/lectures/blackholes/BH_lecturenotes.pdf, (see diff when it was first added to article); Added archive url too
• Added access date for http://authors.library.caltech.edu/14972/1/Ruffini2009p1645Phys_Today.pdf, (see diff when it was first added to article)
• Added archive url for http://www.worldwidewords.org/topicalwords/tw-bla1.htm, (see diff when it was first added in article)
• Added archive url for http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/info_loss.html, (see diff when it was first added in article)
• Added access date for http://www.theory.caltech.edu/~preskill/talks/blackholes.pdf, (see diff when it was first added to article); Added archive url too
• Added archive url for http://relativity.livingreviews.org/Articles/lrr-2008-6/, (see diff when it was first added in article)
• Added archive url for http://www.damtp.cam.ac.uk/user/gr/public/bh_hawk.html, (see diff when it was first added in article)
• Added access date for http://lsag.web.cern.ch/lsag/LSAG-Report.pdf, (see diff when it was first added to article); Added archive url too
• Added archive url for http://www.einstein-online.info/elementary/quantum/evaporating_bh/?set_language=en, (see diff when it was first added in article)
• Added archive url for http://www.nasa.gov/mission_pages/GLAST/science/testing_fundamental_physics.html, (see diff when it was first added in article)
• Added archive url for http://www.eurekalert.org/pub_releases/2008-04/nsfc-nsi040108.php, (see diff when it was first added in article)

--Tim1357 ^talk|poke 17:04, 23 September 2016 (UTC)

Reiteration

quark stars exist, (quark-gluon soup stars), black hole single particles would immediately explode having an infinite decay potential — Preceding unsigned comment added by 2A02:587:4102:CF00:1963:F284:B24D:197C (talk) 05:02, 8 October 2016 (UTC)

How can a black hole grow if mass cannot cross the event horizon for a distant observer?

From the article:

"To a distant observer, clocks near a black hole appear to tick more slowly than those further away from the black hole.[54] Due to this effect, known as gravitational time dilation, an object falling into a black hole appears to slow as it approaches the event horizon, taking an infinite time to reach it.[55] "

OK, but it also says:

"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 holes of millions of solar masses (M☉) may form."

Aren't these two statements contradictory? If it takes an infinite amount of time for the falling object to reach the event horizon, how can the black hole grow? Sure, if you are the object, you will cross it. But for us distant (external) observers, the object never crosses, and therefore cannot add mass to the black hole; therefore, the article is not self-consistent. Can someone please resolve this? Thanks!

Betaneptune (talk) 14:58, 12 October 2016 (UTC)

The former statement says something about what distant observers see/feel/measure. The latter statement says something about what happens locally to the black hole itself. No contradiction. Also note that distant observers feel the influence of the total combined mass of the current BH and whatever in its neighbourhood. For further questions, per wp:talk page guidelines, you probably should try the wp:reference desk/science. HTH. - DVdm (talk) 17:10, 12 October 2016 (UTC)

AST102

This section contains student reviews related to Wikipedia:Wiki Ed/CUNY College of Staten Island/AST102 - Contemporary Theories of the Universe (Fall 2016).

Reading this article makes me think that there are a lot of facts about black holes. For the most part there is but i feel that some of the facts that are thrown in there aren't reliable. While reading this article i clicked on the links and they all lead me to another wikipedia page. I find this interesting because i would think before i even clicked on the links that they would lead me too the actual source. At the end though where the references are located the links that i picked on were in fact reliable.

In the first paragraph there is a sentence where i understand what they're trying to say, and which in fact is relevant. The sentence is "In many ways a black hole acts like an ideal black body, as it reflects no light.[4][5]" The only wrong flaw of this sentence is how it is worded. "An ideal black body" ? They could've just said the color black.

No this article states a lot of point of views of how the black hole theory even came around. The only way i can see this article being biased is of wikipedia only stating the people that believed in the theory vs the people that didn't believe in it.

Clicking on the links they give you down right detail on black holes. The articles explain the specifics around what a black hole is and everything around it.

Jonathanp44 (talk) 03:43, 5 November 2016 (UTC)

Critiques: There is a 5 paragraph lead section that summarizes and gives a general overview of what a black hole is→ this allows readers to get a general idea of the article topic before delving into the details This article is structured in a way that each subtopic within the black hole is given a headline Such a structure provides easy navigation for the reader to quickly find the exact information they are looking for There is an extensive list of the sources used and careful citation at the end to ensure its reliability and give credit

The article Black Hole on wikipedia I noticed right away was of up to the standard quality by the green plus symbol on the top right hand corner which represents a good article. It does not have the symbol for a feature article however and that from reading it I figured was due to the lack of depth. There is a lot of content however, I do believe black holes encompass just so much that can be added to this article in order to put it on par with a potentially featured quality article. Mahwish.razi (talk) 23:24, 20 November 2016 (UTC)

misleading lead

Can we please have a better word choice in the lead? The claim that a black hole is a region is misleading, as it connotes spatial locality, and doesn't do justice to temporal configuration. Further, it would be fairer to characterize the black hole as a physical system, since it has many physical properties beyond simple location.

Holistically, this also doesn't make sense in WP in general, as it is difficult to characterize a black hole as an astronomical object, if it is simply a location. I would do this myself, but apparently the article is locked. 75.139.254.117 (talk) 16:04, 22 February 2017 (UTC)

This was discussed a few times before. IIRC, it seems that the claim that a black hole is a region is properly sourced. - DVdm (talk) 18:54, 23 February 2017 (UTC)

New visualisation tool

Hi, we have just published a new tool that allows to generate black hole visualisations under CC BY SA: http://open.esa.int/black-hole-visualisation-tool/ (Mtrova (talk) 17:20, 23 March 2017 (UTC))

@Mtrova: you sure it works? I can't get [5] to load on Firefox 52 32 bit. VQuakr (talk) 01:36, 20 April 2017 (UTC)

@VQuakr: a bit late, but here's a detailed reply of ESA Advanced Concepts Team developer Alex Wittig:

"As WebGL is a very new technology, it is not uniformly supported yet in all browsers. In order to give a very nice image, we use high resolution textures throughout. The standard does not guarantee support for such high resolution textures on all devices. The problem is a combination of (a) your browser (b) your OS&graphics drivers (c) your graphics card. For example, on my Firefox 52 it all works nicely. We had instances where a change in any of the three components will cause/remove the problem (e.g. FF on Linux fails while same FF on same machine in Windows works).
There are basically two things that can be done (but both would require some effort):
1) Make the error message more descriptive, although it doesn't help the user (it already tells you to try a different browser)

2) Try to downgrade in case of failure and use lower resolution images / redirect to a different website with lower resolution (both degrade the user experience)"

Mtrova (talk) 15:19, 2 May 2017 (UTC)

@Mtrova: it seems to work ok for me now in 53.0. I didn't get an error message before, just a perpetual loading symbol. With it working and appearing to meet WP:External links#What to link, I've added it to the article, [6]. VQuakr (talk) 00:53, 3 May 2017 (UTC)

We should mention ALL theories, even if we don't like them

The Black Hole is a spinning torus with two geysers. There is no central sphere because space doesn't exist in the central region. — Preceding unsigned comment added by 2.84.213.109 (talk) 08:55, 27 May 2017 (UTC)

a black which doesn't spin it immediately explodes, but that can never happen. All black holes spin, and that's an absolute law. Otherwise what you have isn't a black hole phenomenon but either a mistake or some other phenomenon (most times a mistake). — Preceding unsigned comment added by 2.84.213.109 (talk) 09:01, 27 May 2017 (UTC)

Both this post and the reply are nonsense. VQuakr (talk) 16:58, 27 May 2017 (UTC)

Century counting anachronism

from the article:

"The idea of a body so massive that even light could not escape was briefly proposed by astronomical pioneer John Michell in a letter published in 1783-4...

Scholars of the time were initially excited by the proposal that giant but invisible stars might be hiding in plain view, but enthusiasm dampened when the wavelike nature of light became apparent around the early eighteenth century..."

The "eighteenth century" is the 1700s. The "early eighteenth century" would be the early 1700s.

If his letter was published in the late 1700s (the late eighteenth century) how could people have had enthusiasm for it prior to the early eighteenth century (when they ostensibly lost enthusiasm for it)?

--23.119.204.117 (talk) 22:22, 29 May 2017 (UTC)

 Done, with source: see [7], 1801 clearly being early nineteenth century. Good find! - DVdm (talk) 10:45, 30 May 2017 (UTC)

Not even lies can escape it!

That was the old definition, nowadays we know that a black hole loses comparatively to it's mass way more mass than small objects. The "black hole" actually is a self-homologous Kerr ring. — Preceding unsigned comment added by 2A02:587:4110:2700:64F1:9543:4FCE:5ED0 (talk) 04:49, 31 May 2017 (UTC)

External links modified

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I have just modified 2 external links on Black hole. Please take a moment to review my edit. If you have any questions, or need the bot to ignore the links, or the page altogether, please visit this simple FaQ for additional information. I made the following changes:

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• Added archive https://web.archive.org/web/20130526224126/http://www.imamu.edu.sa/Scientific_selections/abstracts/Physics/Gravitational%20Collapse%20The%20Role%20of%20General.pdf to http://www.imamu.edu.sa/Scientific_selections/abstracts/Physics/Gravitational%20Collapse%20The%20Role%20of%20General.pdf

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"proportional" to "inversely proportional" in History > Golden Age > paragraph 5

in History > Golden Age: in paragraph 5 (second to last of the subsection): The last sentence reads "with a temperature proportional to the surface gravity": should it instead read "with a temperature inversely proportional to the surface gravity"? — Preceding unsigned comment added by 137.118.148.52 (talk • contribs) 09:14, 26 June 2017 (UTC)

Please sign all your talk page messages with four tildes (~~~~) — See Help:Using talk pages. Thanks.

The abstract of the cited source says "... temperature of (κ/2π) (ħ/2k) ~ 10-6 (Msolar/M)K where κ is the surface gravity of the black hole ..." — Preceding unsigned comment added by DVdm (talk • contribs) 09:22, 26 June 2017 (UTC)

Schwarzschild radius

Under the section Properties and structure > Physical properties, the Schwarzschild radius should be denoted r_s instead of r_sh. It can be written as r_sh but it would be best to stay consistent with the Schwarzschild radius page (and also with the section Properties and structure > Innermost stable circular orbit (ISCO) which uses the proper notation)

thanover (talk) 14:46, 14 July 2017 (UTC)

 Done Gap9551 (talk) 15:16, 14 July 2017 (UTC)

External links modified

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• Added archive https://web.archive.org/web/20110228234005/http://relativity.livingreviews.org/Articles/lrr-2001-6/ to http://relativity.livingreviews.org/Articles/lrr-2001-6/

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We need clarity on who coined the term 'black hole'

Calling all historians of science. Please go to Wikipedia:Reference desk/Miscellaneous#Coining the term 'black hole'. -- Jack of Oz ^{[pleasantries]} 22:26, 11 September 2017 (UTC)

Semi-protected edit request on 6 October 2017

106.203.72.173 (talk) 01:33, 6 October 2017 (UTC)

Not done: it's not clear what changes you want to be made. Please mention the specific changes in a "change X to Y" format. SparklingPessimist ^{Scream at me!} 01:52, 6 October 2017 (UTC)

Black Hole Burp

Could we get more information about black hole burping?

http://www.bbc.co.uk/news/science-environment-42655685

The Line: "not even particles and electromagnetic radiation such as light—can escape from inside it." May need editing because technically if it burps then particles and gasses do escape?

) — Preceding unsigned comment added by 81.140.92.105 (talk) 10:44, 12 January 2018 (UTC)

The BBC article is vague. The BBC does states that "When cosmic gas comes near one of these sinkholes, it gets sucked in - but some of the energy is released back into space in the form of a burp"; however the energy is "released" from outside the black hole's event horizon while the gas is in the process of being "sucked in" (sic) towards the black hole event horizon; it is not released from inside the black hole event horizon. If the Astrophysical Journal had found a significant amount of energy to come from inside the black hole, that would have been bigger news than the power fluctuation and would have been explicitly called out up-front in both the journal and the news coverage of the journal article. Rolf H Nelson (talk) 18:53, 13 January 2018 (UTC)

Lack of inline citations

Hello, I've just added a good amount of [citation needed] at end of paragraphs without any inline citation because they makes hard to control changes made inside them if the source is too far (where there are any). It may be worth to consider adding Template:No footnotes at the top of the article and reassess it's listing as a Good article. J. N. Squire (talk) 14:27, 4 March 2018 (UTC)

I count ~22 obvious unsourced statements at the end of non-lede paragraphs, so it does seem like it's drifted away from good article status. Thanks for pointing it out. Rolf H Nelson (talk) 02:41, 5 March 2018 (UTC)

@Rolf h nelson: You're welcome. :) I'll consider launching the Good article reassessment if I have enough time.

Please, @Headbomb: is it possible to discuss of this issue here? It looks like you haven't read past the misleading name of the template; we're talking about lack of enough inline citations linked to the footnotes section, here. Deleting every single [citation needed] added by my previous contribution seems rather hasty and extreme when it's not followed by a productive discussion here, and I haven't noticed since then any addition of inline citation to link unsourced statements with references listed at the foot of the article.

Besides, "all [of] those things are supported, there are plenty of [footnotes]" as a summary is vague, missing the point of the lack of enough inline citations (though I admit the name of the template is misleading), and not very helpful regarding the current quality issues of this article (Which addition of mine is superfluous? Why? Ideas to improve the quality? etc.). When I check recently promoted Good articles of other scientific fields like Coyote, I see inline citations in the way I would have wished to find them in Black hole as they seem to be the current best practices.J. N. Squire (talk) 13:15, 5 March 2018 (UTC)

"Very Hungry Black Hole"

https://www.nytimes.com/2018/05/17/science/hungry-black-hole.html NY Times, 5-17-18.

A black hole 20 billion times the mass of the sun eating the equivalent of a star every two days. If it were at the center of our own galaxy, the Milky Way, it would be 10 times brighter than the moon and bathe the Earth in so many X-rays that life would be impossible. Interesting discovery. --Pete Tillman (talk) 15:29, 20 May 2018 (UTC)

Please don't use this talk page to discuss the subject. Article talk pages are for discussing the article, not the subject—see wp:Talk page guidelines. Thanks. - DVdm (talk) 18:57, 20 May 2018 (UTC)

That's an odd comment, as I routinely use this sort of comment to bring interesting new articles to the attention of the community. Surely a new NY Times science article reporting this discovery is notable? I'm not active here, and didn't see your comment until now. I respectfully disagree with it. --Pete Tillman (talk) 03:31, 4 July 2018 (UTC)

@Tillman: it's a comment drawn from the talk page guidelines. I agree that your comment is about an interesting discovery, but it was not about the article Black hole. It reads like an invitation to discuss the discovery, not to add something to the article. I would't have made the comment about wp:TPG if your last sentence had been something like "Shouldn't we say something about this interesting discovery in the article?". In that case someone might have answered: "Yes, perhaps. Wikipedia is yours, so by all means go wp:FIXIT" . - DVdm (talk) 07:34, 4 July 2018 (UTC)

Dark center shadow on the blackhole not comprehensible

Can the article clearly state that the image taken by M87 is/or is not an actual "non processed" image of a blackhole?

A typical blackhole image would simply amplify/lens the radiation sources behind and around the blackhole - causing it to still appear like a bright light source near the centre - not a dark hole. However this image (M87) seems to either be processed (to remove those sources of gravitational lensing) or a simulation.. Only the "absolute center" could perhaps have the black dot. Else it is "just a shadow" like any other shadow - black hole or no black hole.

For the centre of a blackhole to be absolutely dark is pretty much impossible - it would simply be superimposed by radiation sources behind it that would bend and appear to be positioned "on the black hole" to the distant observer.

An alternate source of radiation cannot "just be behind the blackhole" and hence show "the hole/shadow" as explained in text books. There would be millions of sources within a cone 50-100degree from the central axis behind the hole so and they would end up being where the black hole is. This image can only be formed if there was just "1" radiation source behind the black hole - something practically impossible in space. Any other source which would be say 50-100degree off behind the hole would have its radiation lensed to superpose the position of the black hole to the distant observer.

Please do not delete this edit. I am challenging the hypothesis posted in the article citing the image - as a piece of blatant scientific lies- trying to morph data to fit it into imagination to win public opinion. M87 is probably more of an imagination rendered via code to force data fit into it rather than a real image. — Preceding unsigned comment added by 27.59.47.227 (talk) 05:29, 18 April 2019 (UTC)

It's a consequence of general relativity; rather than following the straight lines of force from newtonian mechanics, which are founded in euclidean geometry, in free fall we instead follow the geodesics of spacetime. Light follows these geodesics (although photons have no mass) as well, by Maxwell's equations. These terms are enough to follow this video: How to Understand the Image of a Black Hole. I would recommend starting at minute 2:30 for the answer to your good faith contribution. Briefly, the video explains why light does not follow straight lines in this situation. --Ancheta Wis   (talk | contribs) 11:37, 18 April 2019 (UTC)

I am following the general relativity concept. General relativity only multiplies the Newtonian divergence by a factor of 2. It in no way implies "a hole", any random source ,and infinite such sources could be in a plane behind the black hole to be able to give a divergence that shrinks the hole itself.

I suggest you check if that video, when defining the event horizon, event considers that there are millions of sources behind the black hole at different distances behind the black hole. All rays dont "just pop up in front like that" - or go around and not "bend to not come out in front of the black shadow of the hole".

Just like a million satellites being sling shot around the earth towards the moon at different angles and entering the gravitational field different places around the earth's circumference - will the satellites never cover the face of the earth as seen by an observer on the moon?

The "b", as we put it in text books, (the elevation of the straight line path between the observer and the source, above the point mass equivalent of the black hole) can be anything , and the "b" itself is used in the derivation after an approximation. The image of a black centre still does not add up.

The video (around 5:20 sec) assumes loads of parallel rays coming from the back, and just that back- not diagonally across from the back either, and then sinking in and some making it out. That wont be the case in reality - those parallel rays are "not just rays from the back of the blackhole hitting it from the back side" but also those form diagonally back, diagonally up and diagonally below. Trace the path of those rays on a simulation- Even with the Newtonian factor of 2 for alpha (deviation angle) or a factor of 4 for alpha (deviation angle) from relativity, with loads of random sources behind the hole, you won't get that "hole" :-)

— Preceding unsigned comment added by 49.205.218.102 (talk) 14:31, 18 April 2019 (UTC)

NE surface

I don't know the proper terms for my thoughts. Using our solar system as the base of this idea and knowing over a century ago most planets, except Mercury, obeyed Newton's gravitation laws. This means to me there is a NE surface (NE surface for Newton-Einstein) in which Newton's gravitation laws break down and Einstein's relativity takes over between Venus and Mercury. I know this sphere is not well defined (like the line for Earth and outer space being 60 miles) What is the radius of this NE surface with black holes? Can an article section talk about this? John W. Nicholson (talk) 00:18, 1 October 2018 (UTC)

As a gravitational field gradually becomes more intense, relativistic effects gradually become more important; there is no dividing line or surface where this occurs suddenly. WolfmanSF (talk) 00:59, 1 October 2018 (UTC)

I think I said that too, but I also realize that there is a point when predictions of Newton are so off that one must use Einstein's predictions. That point is on a surface of other points predictions. I guess I am trying to understand when and where margin for normal Newtonian effects and relativistic effects become more important than the other for black holes. John W. Nicholson (talk) 21:22, 1 October 2018 (UTC)

“are so off”? Is that 5%? 1%? 1ppb? For this to be of interest to Wikipedia, someone else has published these calculations before. —SmokeyJoe (talk) 22:51, 1 October 2018 (UTC)

Surface of last influence

Why is there no mention of this? Seems pretty important. You can read about it in Gravitation by Misner, Thorne, and Wheeler, section 33.1 starting on p. 872. Betaneptune (talk) 01:03, 14 January 2019 (UTC)