With good quantization, I bet we can get it down to 8B and it will easily fit on consumer grade galaxy.
(Sorry, I had to, with all the AI flood, I really was about to skip this info after the first 3 characters)
ghurtado · 1h ago
Don't be sorry, that was pretty good
freddier · 1h ago
They very rare great HN joke.
deafpolygon · 54m ago
that's too good, haha
dweinus · 4h ago
Using the formula for black hole density, a black hole of this mass would have an average density about the same as the near-vacuum atmosphere of Mars(!)
And it would take 10 days from event horizon to the singularity.
dotancohen · 1h ago
How so?
proteal · 1h ago
The black hole has two conceptual parts - the event horizon and the singularity. The event horizon is a one-way imaginary shell where once you pass it, you will end up at the singularity which is a point at the center of the event horizon. It’s the hole in black hole. Because the radius of the spherical horizon grows linearly with mass, but the size of the hole is fixed at effectively 0, it allows for a bit of sightseeing on your way to impending doom if the mass of the hole is large enough.
reactordev · 1h ago
This is also the light barrier where light can no longer escape the gravitational forces (causing the blackness of the black hole).
Your “sightseeing tour” would be a kaleidoscope of light as it brushes past you on its way to the singularity.
BSOhealth · 4h ago
With all the lensing going on out there, is it possible for us to observe the light from our sun (and potentially our planet) billions of years ago?
A cool achievement would be, observe the moon/earth separation event(s)
throwup238 · 4h ago
Theoretically yes but although this black hole is big enough to make that more realistic, the redirected light would be have lost so much energy we’d likely be unable to observe it. We’d need an orbital hypertelescope to even stand a chance. Even then we wouldn’t see the earth because it would be drowned out by the sun.
The bigger problem is all the dust and other stars in the way. I’m not aware of any black holes close enough that would have a direct path for the light to cross without being absorbed and scattered.
LeifCarrotson · 2h ago
The other problem is the angle at which the light must be redirected. The Cosmic Horseshoe is composed of two systems almost directly in line, the light comes from the farther system and bends infinitesimally around the black hole to come to us. I don't know if a 180 degree bend is possible.
Also, the foreground galaxy/supermassive black hole in the Cosmic Horseshoe is 5.6 billion light years away, so any light that could come from our solar system, go around the black hole, and come back to our hypothetical hypertelescope would be over 11 billion years old - almost triple the age of our sun.
Saggitarius A* in our own galaxy is, of course, directly in the elliptic and therefore badly occluded by dust, but it would be interesting to look at as it's only 27k light years away. In the absence of that pesky dust, it would give us a picture of the solar system as of the Paleolithic. Andromeda, at 2.5 million light years away, would give us 5-million-year-old light. There are other black holes in the Milky Way on the order of a thousand light years away which are not at the center of the galaxy but have masses comparable to or slightly larger than our sun, these are far closer (within a few thousand years) but have much smaller gravitational fields. Luminous intensity drops off with the square of the distance, but I'm not sure how the gravitational field strength affects the ability of a particular galaxy to bend light.
throwup238 · 1h ago
> The other problem is the angle at which the light must be redirected. The Cosmic Horseshoe is composed of two systems almost directly in line, the light comes from the farther system and bends infinitesimally around the black hole to come to us. I don't know if a 180 degree bend is possible.
It is possible to get a deflection angle of 180 but under a few million solar masses, hitting the “sweet spot” in between the photon sphere and the boundary of the shadow would basically be a once in the lifetime of the universe type probability, if it were possible at all. At billions of solar masses that sweet spot become much bigger, but then those are much further away.
ghurtado · 1h ago
> almost triple the age of our sun.
In this insanely hypothetical scenario, would it be possible to see a sun before our sun? (In the same galactic vicinity)
chiffre01 · 4h ago
How big would the diameter of this be ? Something like 8 light days ?
myrmidon · 2h ago
Sounds about right. Wiki has a correctly scaled picture with the two biggest known black hole event horizons and the solar system:
A bit off topic: Is there any theoretical upper limit on the mass of a black hole?
MurkyLabs · 4h ago
It doesn't seem like there's a limit to how big they can get just a limit to how quickly they can get bigger due to what's called the Eddington Limit which explains how matter falling into the black hole emits radiation and if enough radiation around the accretion disk builds up, it can overcome the pull of the black hole and push matter away, at least until enough matter is pushed away that the radiation levels fall back under the limit and matter starts falling in again.
qualeed · 3h ago
PBS Spacetime had an episode somewhat recently about a black hole which is growing at many (hundreds? thousands? I forget) times the Eddington Limit. And, as far as I remember, it isn't the only one to exceed the Eddington Limit - just the one with the record for how much it exceeded it.
I'll try to dig it up when I'm not at work (or if I remember the exact episode through the day).
orra · 7m ago
I remember this episode too. The answer is four thousand times bigger than the Eddington Limit. Blimey!
Importantly, the Eddington limit does not apply to black hole mergers, theoretically allowing as much growth rate as you're able to feed in from smaller black holes.
allemagne · 3h ago
So then the only theoretical limit on black hole mass would just be how fast you can put matter in black holes and/or merge existing black holes versus how fast the universe expands?
MurkyLabs · 2h ago
I'm 100% an armchair physician so take my words with a grain of salt but it seems like according to the math there is no limit to how massive a black hole can get. There are limits on the size of how big and small things can get and how hot or cold they can get, the second part is pretty cool, Physics Explained on yt has a good video on it (he's got a lot of good videos) but I enjoyed this one on what the maximum temperature is in the universe: https://www.youtube.com/watch?v=NVlEQlz6n1k
ghurtado · 1h ago
> I'm 100% an armchair physician
Not to be that guy, but a physician is a doctor.
dotancohen · 1h ago
But that's not important right now.
ghurtado · 19m ago
Just pointing out a simple mistake.
In the time that it took you to type that response, you could have learned 10 new words.
I do it because I appreciate it when people do it for me.
That was the purpose of my comment. What was the purpose of yours?
> [270B solar masses] is the maximum mass of a black hole that models predict, at least for luminous accreting SMBHs.
as well as:
> The limit is only 5×10^10 M [50B solar masses] for black holes with typical properties, but can reach 2.7×10^11 M [270B solar masses] at maximal prograde spin (a = 1).
However in the chapter before, it's stated:
> New discoveries suggest that many black holes, dubbed 'stupendously large', may exceed 100 billion or even 1 trillion M.
throwaway81523 · 3h ago
There's a theory that the universe we live in is itself inside a giant black hole. No idea how it is supposed to have gotten so biig.
I know this article. It's citing a bunch of speculative hypothesis by mostly this one person which relies on something super exotic called Einstein Cartan theory. I stand by my statement. I even suspect the article was written by them.
I hate random links being thrown at me, because I don't know what you are trying to tell me. Perhaps you can spare a few key strokes.
For everyone else reading the thread, let me summarize. The article agrees with me:
> the entire observable universe exists within a black hole—except, that is, for all the evidence to the contrary
>....
> It does not seem likely that we live inside a rotating universe, let alone a black hole.
MarkusQ · 1h ago
You have elsewhere in this thread objected to people providing links without giving context, so I hope you won't mind being asked to unpack this claim a little. Why is it nonsense? If, as you say, it's principally pushed by one person, who is that, and why does that argue against it?
(I'm not thinking this is too much to ask; saying it's wrong might require empirical support, but the claim that it's "nonsense" should be easier to justify.)
mr_mitm · 1h ago
First of all, black holes have an interior and an exterior. Our universe only has an interior. Next, black holes have a singularity into which everything vanishes, or at least moves towards. Im our universe, everything moves away from a singularity. So if anything, it resembles a white hole more than a black hole. Also, our universe is expanding, whereas black holes shrink (unless matter falls into them, which can't happen to our universe because it has no exterior).
It really looks nothing like a black hole.
abtinf · 1h ago
> giant
How would we know the size? Relative to what?
BurningFrog · 4h ago
So what happens if two such black holes collide?
msk-lywenn · 4h ago
Can black holes even collide? I guess their horizons can merge somehow... Probably a spectacular show.
I love to contemplate galactic-scale synchrotrons that accelerate supermassive charged black holes to collide at relativistic speeds. The thought never really goes anywhere, but I'm sure it'd be a spectacle to behold.
Poking around those articles (and knowing nothing really), it is interesting to note a couple references to a 50B solar-mass limit for “luminous accreting black holes hosted by disc galaxies.” (In your Phoenix cluster link). I guess these ones are easier to spot, based entirely on the word “luminous.”
There are other larger ones out there, looming in the darkness.
bell-cot · 39m ago
Yes - but it's basically the same as the total mass of the universe.
EDIT: I believe the above could be incorrect - if the universe has too much electrical charge or angular momentum. (And some other cosmological properties, so you couldn't get around the charge & spin issues.)
Might there be a black hole astrophysicist in the house, to comment on this?
(Sorry, I had to, with all the AI flood, I really was about to skip this info after the first 3 characters)
https://physics.stackexchange.com/questions/26515/what-is-ex...
Your “sightseeing tour” would be a kaleidoscope of light as it brushes past you on its way to the singularity.
A cool achievement would be, observe the moon/earth separation event(s)
The bigger problem is all the dust and other stars in the way. I’m not aware of any black holes close enough that would have a direct path for the light to cross without being absorbed and scattered.
Also, the foreground galaxy/supermassive black hole in the Cosmic Horseshoe is 5.6 billion light years away, so any light that could come from our solar system, go around the black hole, and come back to our hypothetical hypertelescope would be over 11 billion years old - almost triple the age of our sun.
Saggitarius A* in our own galaxy is, of course, directly in the elliptic and therefore badly occluded by dust, but it would be interesting to look at as it's only 27k light years away. In the absence of that pesky dust, it would give us a picture of the solar system as of the Paleolithic. Andromeda, at 2.5 million light years away, would give us 5-million-year-old light. There are other black holes in the Milky Way on the order of a thousand light years away which are not at the center of the galaxy but have masses comparable to or slightly larger than our sun, these are far closer (within a few thousand years) but have much smaller gravitational fields. Luminous intensity drops off with the square of the distance, but I'm not sure how the gravitational field strength affects the ability of a particular galaxy to bend light.
It is possible to get a deflection angle of 180 but under a few million solar masses, hitting the “sweet spot” in between the photon sphere and the boundary of the shadow would basically be a once in the lifetime of the universe type probability, if it were possible at all. At billions of solar masses that sweet spot become much bigger, but then those are much further away.
In this insanely hypothetical scenario, would it be possible to see a sun before our sun? (In the same galactic vicinity)
https://en.wikipedia.org/wiki/TON_618
Event horizon radius would be about roughly 1000 times the distance between Earth/Sun.
https://en.m.wikipedia.org/wiki/Cosmic_Horseshoe
I'll try to dig it up when I'm not at work (or if I remember the exact episode through the day).
The episode is called “The NEW Ultimate Energy Limit of the Universe”. https://youtube.com/watch?v=0rzgYzbzq5Q
Not to be that guy, but a physician is a doctor.
In the time that it took you to type that response, you could have learned 10 new words.
I do it because I appreciate it when people do it for me.
That was the purpose of my comment. What was the purpose of yours?
> [270B solar masses] is the maximum mass of a black hole that models predict, at least for luminous accreting SMBHs.
as well as:
> The limit is only 5×10^10 M [50B solar masses] for black holes with typical properties, but can reach 2.7×10^11 M [270B solar masses] at maximal prograde spin (a = 1).
However in the chapter before, it's stated:
> New discoveries suggest that many black holes, dubbed 'stupendously large', may exceed 100 billion or even 1 trillion M.
For everyone else reading the thread, let me summarize. The article agrees with me:
> the entire observable universe exists within a black hole—except, that is, for all the evidence to the contrary
>....
> It does not seem likely that we live inside a rotating universe, let alone a black hole.
(I'm not thinking this is too much to ask; saying it's wrong might require empirical support, but the claim that it's "nonsense" should be easier to justify.)
It really looks nothing like a black hole.
How would we know the size? Relative to what?
https://www.youtube.com/watch?v=doS85Mh78Vc
This is what they look like when they merge, its pretty darn cool
https://scitechdaily.com/cosmic-heavyweights-collide-ligo-de...
No comments yet
There are other larger ones out there, looming in the darkness.
EDIT: I believe the above could be incorrect - if the universe has too much electrical charge or angular momentum. (And some other cosmological properties, so you couldn't get around the charge & spin issues.)
Might there be a black hole astrophysicist in the house, to comment on this?