Talk:Stellar black hole

BH masses
Some of the masses in the table for the companion object are impossibly small. I notice Cygnus X-1 in particular, where the companion star is an O9.7Iab, and must have a mass of roughly ≥20 solar masses. The table gives 0.25, and I think this might be the so-called mass function. The Uhuru X-ray source 4U 1543-475 is a similar case, but I do not know the lower limit.

Comment: The lower limit for a start to turn into a black hole is probably something like 20 solar masses. 8 solar masses is the limit for a supernova. At this mass a core of more than 1.44 solar masses remains, above the Chandrasekhar limit. The limiting mass of a neutron star is unknown (only that most neutron stars have a mass close the 1.4 solar masses), and it is also unkown how much of the mass will end up in the compact object in a supernova explosion. Therefore, the exact mass a star must minimally have to end in a black hole is unknown as well. —Preceding unsigned comment added by 212.123.164.6 (talk) 19:50, 27 July 2010 (UTC)

I don't have time to check all these right now, but will put it on my list (meaning it could be a while). For now I have changed the "Mass" column heading to be BH mass, and the other to be "Companion Mass", but estimates for the mass of the optical companion need to be distinguished from the mass functions (which are easier to determine observationally, but only constrain the masses, don't determine them unless the orbital inclination is known). If the mass function is meant, then the column heading should so indicate, and define it (we don't seem to have an article that does that, but I only checked the article on binary stars). Wwheaton (talk) 00:05, 10 April 2008 (UTC)

The end of the first paragraph reads "with a mass 3.8 solar masses and a diameter of only 9 kilometers (15 miles)." I suspect the numbers are reversed since 15 kilometers is roughly 9 miles.

Black hole velocity
The article currently states:

"'A black hole can only have three fundamental properties: mass, electric charge and angular momentum (spin).'"

Wouldn't a black hole also have a velocity in space, relative to other objects? Gravitational attraction is a two-way street, after all.

-- Rogermw (talk) 22:00, 27 October 2009 (UTC)


 * Yes, and a position also, but these are generally not considered fundamental properties in the sense that they are not intrinsic to the black hole, since they only have meaning relative to other objects. This may need to be clarified a bit though. (TimothyRias (talk) 09:06, 28 October 2009 (UTC))

A bit silly.
Im not challenging the "citation needed" tags, just so its clear. But there seem to be a silly amount of them. Should we just replace it with a template stating such? Since theres not many people who could really write up the accurate information, i think the citation needed template would make the article, flawed though it may be, much more readable. Not going to change it right away incase there are disagreements. 74.132.249.206 (talk) 07:12, 9 August 2011 (UTC)


 * I'd say leave the "citation needed" tags since they identify exactly what statements are in need of citation. I'll try to fix some of them now.TR 09:25, 9 August 2011 (UTC)

Prompt collapse
The article states: "The process is observed as a supernova explosion". 1) This sentence is only partially true: BHs can indeed be formed via prompt collapse, i.e. no intermediate protoneutron star stage. Within this scenario, no SN happens: matter directly collapses into the BH. For reference: http://arxiv.org/abs/1110.1635 2) Also, it is not very correct to speak about "observing" the process. Shesinastro (talk) 21:45, 21 October 2011 (UTC)

largest known
The article says:
 * The largest known stellar black hole (as of 2007) is 15.65±1.45 solar masses.

Since 2007 there have been some claims of significantly larger stellar black holes. Are these solid enough to be worth adding? This NASA press release discusses an object claimed to be between 24 and 33 solar masses, citing a paper to that effect, which seems reasonably legit. I'm not knowledgeable enough about the literature here to feel comfortable adding it, though. Our article in general already seems a little bit hodge-podge on these kinds of claims; do any recent survey papers of this area exist that we could cite for a more solid overview? --Delirium (talk) 16:02, 17 December 2011 (UTC)


 * There is a paper about this which seems to me to be a 'reliable source' here with a summary and citations here. It looks as though it should be on the list or at least on the page of candidates if not considered sufficiently robustly determined. George Dishman (talk) 12:35, 19 July 2017 (UTC)

Properties
The arcticle states:

"'In February 2016, a black hole of 62±4 solar masses was discovered in gravitational waves as it formed in a merger event of two smaller black holes.'"

Wouldn't this item more properly belong on the page for Intermediate-mass black holes? The formation process, a merger, would seem more important than the exact mass of the resulting black hole (i.e. above an arbitrary 100 M_sol). The object formed is also substantially more massive than the most massive previously known stellar black hole.Pnikula (talk) 06:43, 12 February 2016 (UTC)


 * If "the page for Intermediate-mass black holes" means the Wikipedia article "Intermediate-mass black hole", then I think the experts have spoken, in deciding that the class of "solar mass" or "stellar" black holes, includes black holes that [quote]: "have masses ranging from about 5 to several tens of solar masses." (quote from the "current" or "most recent" version of Stellar black hole)


 * ...and that the class of "supermassive" or "even bigger" black holes, is defined to include those whose mass is "on the order of hundreds of thousands to billions of solar masses " (quote from the "current" or "most recent" version of the Wikipedia article "Supermassive black hole".)


 * Oops, sorry ... I did not intend to leave out this: (The first ["lede"] sentence of [the article about] Intermediate-mass black hole[s]) : "An intermediate-mass black hole (IMBH) is a hypothetical class of black hole with mass in the range 100 to one million solar masses: significantly more than stellar black holes but less than supermassive black holes."This is probably where that "threshold" of 100 (the threshold that is being questioned) was mentioned. --Mike Schwartz (talk) 23:11, 27 April 2016 (UTC)


 * I do not know why the threshold of 100 was chosen. I do not know whether it is indeed an "arbitrary" size or not. That is probably an issue for the experts in this field (this branch of science). I think that Wikipedia policy generally is to just adopt and follow (carry out) the accepted linguistic or "taxonomic" customs in any given field of study ("scientific" or otherwise.)


 * I hope this helps. --Mike Schwartz (talk) 21:04, 19 April 2016 (UTC)

"When published" is not the same as the date when a certain thing was discovered
The article states:

"'In February 2016, a black hole of 62±4 solar masses was discovered in gravitational waves as it formed in a merger event of two smaller black holes.'"

IMHO that is wrong. The paper about the discovery was published (and the public announcements were released) "In February 2016"; but the "discovering" itself (by the LIGO project) had taken place during September 2015.

So, IMHO, either the "as of" date in that sentence (the sentence that is "blockquote"ed above) should be changed to "September 2015" -- as is clearly supported by many reliable sources, such as those that are cited in the article about First observation of gravitational waves (in the section about "The GW150914 event") -- or else, the verb in that sentence should be saying something about when the paper was published, and/or when the announcement was made publicly, instead of talking about when the large black hole was "discovered".

(Comment: the name "GW150914" itself -- as in "The GW150914 event" -- is derived from the date "September 14, 2015".)

(another comment): The footnote or "reference" will not have to change. It already points to a reliable source with a URL of http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.061102 and -- in the full text of that paper [which is available at that URL, even though part of the URL might "seem" to be implying that it is (only) the "abstract"!] -- it clearly states, at the beginning of section "[Roman numeral] II" (the section with a title of "II. OBSERVATION"), that "On September 14, 2015 at 09:50:45 UTC, the LIGO Hanford, WA, and Livingston, LA, observatories detected the coincident signal GW150914 shown in Fig. 1." ...So, actually, making the "edits" (changes) suggested here, will make this Wikipedia article more consistent (not less) with what that source says.

Suggested possible "edits" (changes)

 * 1) date change: "'In September 2015, a black hole of 62±4 solar masses was discovered in gravitational waves as it formed in a merger event of two smaller black holes.'"
 * 2) verb change: "'In February 2016, it was announced that the LIGO project had detected, via gravitational waves, the formation of a black hole of 62±4 solar masses in a merger event of two smaller black holes.'"

I vote for the first option (the "date change"). --Mike Schwartz (talk) 18:04, 19 April 2016 (UTC)

CASE CLOSED (April 27, 2016)
With no dissent (at least, on this "Talk:" page) after about a week, the first option (the "date change") was implemented by this simple edit.

--Mike Schwartz (talk) 22:53, 27 April 2016 (UTC)

Missing: estimate of tidal force on human body
The article Supermassive black hole estimates the tidal force at the event horizon of a supermassive black hole as roughly similar to that experienced on Earth. The present article needs a similar estimate for stellar-sized BHs. David Spector (talk) 16:02, 20 August 2018 (UTC)
 * It would be so far off the scale that it'd be meaningless. See spaghettification.  Although yes, it would be fun to see just how ridiculously strong the tidal force would be ... I read a book once, by Kip Thorne, which begins with a story about a robot doing just what you're thinking about. It doesn't give a whole lot of numbers, but from what I remember the robot survived for about a tenth of a second and that was despite being a very small robot.  — Soap — 04:23, 5 December 2019 (UTC)
 * Actually, since the radius of a black hole is directly proportional to the mass, but the tidal force diminishes according to the cube of the radius, all we need to do is square the ratio of any two black holes to find the ratio of the tidal forces at their edges. Thus, a 10-solar mass black hole will have a tidal force one trillion times stronger at its event horizon than a 10-million solar mass one. — Soap — 04:37, 5 December 2019 (UTC)
 * To put this in more humanly understandable numbers, if I'm reading the end of tidal force right, a human at the edge of a stellar mass black hole would feel a pull of about (1.1 × 10−7g) * (1012) =  110,000 g. — Soap — 04:42, 5 December 2019 (UTC)

I plan to put this into the article soon as you recommended, but have held back so far because the original data point is extremely vague. "About the same" might be off by as much as a factor of 10. I could do the math properly by just starting with the tidal force equation, but havent gotten around to it yet. — Soap — 22:55, 10 December 2019 (UTC)

Expected abundance
I have read that "108 black holes are estimated to reside within the Milky Way". A reader might get the impression from the article that there are much fewer. Could someone knowledgeable write something about the expected abundance? Keith McClary (talk) 22:34, 19 March 2019 (UTC)

Will Schwarzschild Radius for Each Black Hole be informative?
Schwarzschild_Radius is given by
 * $$ r_s = \frac{2 G M}{c^2} $$

Computationally, =(2*(6.67408*10^-11)*M*(1.9884*10^30))/((299792458)^2)/10^3

Bkpsusmitaa (talk) 14:48, 2 December 2018 (UTC)

Is there a defined way to flag Start-class identified articles like Stub-class articles are flagged?
This article appears to be ambitious in range but it has been identified in this talk section as early in its development.

Is there a standard way to alert the Wikipedia reader when a source is Start-class in the way Stub-class articles are flagged?

It may even prompt a student or professor to make it an assignment. ReedScarce (talk) 17:54, 24 February 2022 (UTC)

GRO J0422+32/V518 Persei has a significantly smaller mass, so it is not a candidate.
Analysis in 2012 calculated a mass of. Voproshatel (talk) 08:30, 3 April 2024 (UTC) Voproshatel (talk) 08:33, 3 April 2024 (UTC)