Talk:S5 0014+81

Size

The part that says, "this black hole has the diameter of 236.7 billion kilometers, or 47 times the distance from the Sun to Pluto". Isn't this somewhat misleading comparing the entire diameter of the black hole to what I'm guessing is some average distance of Pluto to the Sun? Shouldn't we be comparing the radius? Stated as such the average person would assume the black hole is 47 times the size of our Solar System, as measured by the orbit of Pluto. (Granted, not the actual edge of the Solar System anyway, but most people don't concern themselves with anything outside the orbits of the planets... and do still consider Pluto a planet... but those are separate issues.) What bothers me is that unless one reads this carefully it builds a mental image of the black hole being twice as large as it is. It's already enormous, and doesn't need to be further inflated.

tl;dr Why compare a diameter to what is effectively a radius? This apples to oranges comparison, while accurate, is confusing. Like should be compared to like, and thus either the black hole's radius or the diameter of Pluto's orbit should be substituted. 50.204.97.60 (talk) 00:14, 26 February 2015 (UTC)

@50.204.97.60 This part does not to be reworded. It is easy to understand hence, no change is required. hi (talk) 20:40, 20 April 2015 (UTC)

The allegued diameter of 236.7 billion km is not clear. Is it the ergosphere or including the accretion disk ? If you base the calculation on the Schwarzschild radius, then it is not the size of the "black hole" but of its external horizon. So I corrected the text accordingly.-- luxorion

I don't understand this statement. A layman will be able to understand that the determination of the size of the black hole was its event horizon. The ergosphere is just basically a zone where an object crossing on it can achieve great potential energy to escape. SkyFlubbler ^(talk) 14:19, 12 February 2016 (UTC)

"175 times the size of the Milky Way"

I'm a layman, but this seems inaccurate if it's also only (only being a relative term here, of course) 37.4 times the diameter of Pluto's orbit. While this is very large, surely the Milky Way, being a Galaxy, is much larger, and the word "size" would seem to indicate physical dimensions. Or is mass meant? If so, wouldn't using the word mass be clearer? 144.32.240.167 (talk) 07:56, 11 February 2017 (UTC)

I agree that this is highly ambiguous, but one should make a distinction between the size of its central black hole (where the 37.4 figure is mentioned) and the galaxy as a whole. This article doesn't seem to make such a distinction, however, and I'd be inclined to remove such statements as unverifiable.--Jasper Deng (talk) 09:00, 11 February 2017 (UTC)

Size as a multiple of Pluto's orbit

The size of the event horizon of S5 0014+81 is miscalculated by a factor of two. The claim for the black hole mass is referenced and is not disputed. Taking this value of 40 billion suns and using the formulae for the Schwartzchild Radius, one gets a radius of 1.19x10^14m. This fits with the claimed diameter of the black hole of 236.7 billion km (note radius is half a diameter). But the semi-major axis of Pluto is 5.9x10^12m. Now, the semi-major axis is a value approximating to the mean orbital radius, not diameter, so the correct ratio is 1.19x10^14 / 5.9x10^12 = 20 times the size of Pluto's orbit, or roughly half the value given. Consideration to correcting this claim please. Billysugger (talk) 23:38, 25 July 2017 (UTC)

• Billysugger, I believe what was meant was that the event horizon is 37.4 times Pluto's semi-major axis or orbital radius rather than the diameter of it's orbit or orbital diameter. For a layman it makes more sense to me to describe the width of the black hole in terms of how many times wider it is than the distance from the Sun to Pluto then it does to describe it in terms of how much wider it is than the major-axis. So I've changed it from diameter to radius, and also from 37.4 to about 40. Mr rnddude (talk) 12:11, 7 August 2017 (UTC)
  • I don't think it makes a lot of sense to compare half the major axis of one thing (Pluto's orbit) with the entire major axis of another. --Doradus (talk) 04:10, 25 February 2018 (UTC)