Scientists spot massive black hole collision that defies current theories Researchers have observed the largest ever collision between two massive black holes witnessed by humans, a finding that’s sent astrophysicists back to their calculators to re-think models. Astroboffins spotted the aftereffects of the event on November 23, 2023, when they detected emissions from two huge black holes, each …
I think they're saying blackholes bigger than 100x the sun can't form from supernova, because there are plenty big ones around and thought to occupy the centre of many if not all galaxies. Why were these spinning so fast, is it just conservation of momentum? What happens when 2 rapidly spinning objects merge? Unless they conveniently merge along the same axis, spinning similarly, one imagines it will be very violent.
It's been a lonnng time since I read up on this stuff, so I've probably forgotten most of it.
But I think the Supermassive Black Holes at the centre of Galaxies, are believed to have a different origin than "Stellar" Black Holes (those formed from Supernovas). My memory says there were two theories, one was simply they formed closer in time to the Big Bang and so were able to gobble far more in that condensed space than would be possible nowadays, and the other was something to do with early Dark Matter, which frankly I cant remember.
You are right the 100x limit is believed to be the biggest you could get from a single Supernova. I guess if you add them together you should be able to get above 100x, but I think there was something about inherent stability, which they thought would cause the newly formed Black Hole to shed mass.
Gahh now I'm going to have to go back and try and find all those old notes from Uni... Although they are probably massively out of date by now... :P
Some mass is lost during the collision (as the gravitational waves) but the only other known mechanism for a black hole to lose mass is Hawking radiation, however stellar mass black holes will take many orders of magnitude longer than the current age of the universe to evaporate by that mechanism, and only after there's no matter left to swallow.
I had the same question and went through various AI's on this. Sadly, this is wrong. None of the mass inside the Event Horizon is ejected. The 15 Stellar Mass discrepancy comes completely from rotational energy outside of the Black Holes. i.e. this is completely unlike Hawking Radiation, and I really pressed on all of the pro models of AI and they went into some detail on why this is different. Apparently a consequence of GR, zero of this mass comes from within the Event Horizon (and I also figured, like you, that it must be mass/energy from inside being reclaimed from the black hole, but nope!).
Angular momentum is related to the moment of inertia which, for a sphere is (2/5)mr². Assuming the singularity at the centre is both spherical and has a non-zero but vanishingly (literally!) small radius, the angular momentum may not be as large as you may imagine.
That said, it's a situation where a small change of n in the x 10^n part of r is likely to make a colossal difference given the size of m
Intriguing questions....
Nearly all observed black holes are either <100 Solar masses and are called Stellar black holes, or >100,000 Solar masses (with some in the range if billions of solar masses) and called Super massive black holes. So there must be two different ways of black holes forming. The small ones are from supernovas, what made super massive blacks holes in unknown.
"The small ones are from supernovas, what made super massive blacks holes in unknown."
Possibly assembled from numerous collisions/mergers of stellar black holes. At the rate the LIGOs and now the LVK Collaboration are detecting them, these may not be very rare events. Possibly even more frequent in an earlier, more dense universe.
Those so-called supermassive black holes found at the center of galaxies were formed differently, in the very early days of the universe. Probably from direct collapse - same way stars are formed but so much material was concentrated into one spot it skipped the "star" stage and went directly to a black hole, some possibly born at millions of solar masses.
Rochester Institute of Technology has people modeling these events. The spins of the original black holes really warps the space-time around the objects and results in gravitational waves being emitted preferentially in one direction. In this case, the missing 15 solar masses is emitted in one direction and the resulting black hole is kicked in the opposite direction (as much as .01 times the speed of light). During the last seconds of the event, the spins of the incoming black holes rotates by a large amount.
I wouldn't want to be near any such event.
the resulting black hole is kicked in the opposite direction (as much as .01 times the speed of light)
I've seen speculation that the reason the Milky Way's supermassive black hole is so small (only 4 million solar masses, when most galaxies our size have SBHs in the billions of solar masses) is because after one of our galaxy mergers in the distant past our SBH eventually merged with the other galaxy's SBH and got a big enough kick to leave the Milky Way behind forever. The runt SBH we have now came from when our galaxy "consumed" a much smaller satellite galaxy long ago.
,.. and as (according to Hawkins) the angular momentum is conserved in formation of a black hole, which is now very much smaller than its original constituents, the internals of the black hole are rotating still at very much higher spinning rate than that.
,.. and as (according to Hawkins) the angular momentum is conserved in formation of a black hole, which is now very much smaller than its original constituents, the internals of the black hole are rotating still at very much higher spinning rate than that.
i wonder if that speed of rotation might be FTL which is why we can't see light from them? like the event horizon is that last speed range we can see before SOL is surpassed?
the universe is a huge, wondrous, and mysterious place... we humans are just beginning to understand small amount of what goes on out there :)
My "back of a fag packet" calculation gives a similar result:
Earth spins at approx 1,000 MPH.
So, 400,000 times this is 400,000,000 MPH - which is 111,111 miles per second = about 4.5 Earth rotations every second = 270 RPM
And cross checking with the wiki, which gives the "Equatorial rotation velocity" as 0.4651 km/s
So, 400,000 times = 186,040 km/second (which is about 116,275 miles per second, which is close enough to the above !)
So does this mean that intermediate-mass black holes are no longer theoretical? Or are they extending the range classed as Stellar-mass black holes? Up to now, I believe the intermediate-mass range of 100 to 100,000 stellar masses had a few candidates, but no confirmed members, so this would seem to be the first confirmed member of that class, unless there's some nuance I'm missing.
This is not the first confirmed detection above 100 solar masses. The reason this event is in the news is that it's the largest remnant so far detected, and is very close to the theoretical detection limit of our current detectors.
There have been three previous detections in the ~140 solar mass range and one of ~170, in 2019 and 2020, although the range of mass uncertainty is quite wide for some of them.
When a black hole forms, it will be < 100 SM. Mass loss from within any event horizon is by definition not possible (pace a very slow leak of Hawking radiation). Ergo a colliding pair in the 50 - 100 SM range will result in in one of 100 - 200 SM range. We keep observing collisions. Nothing forbidden about any of that. Accompanying gubbins from the comparatively modest accretion discs and EM fields may be lost, but it is loss of the main mass within that is forbidden.
Sorry, not from inside the hole, no. The /only/ thing that can escape from there is Hawking radiation, which in this scenario is insignificant. The source of any radiated energy /must/ come from something else.
Gravitational energy in this sense is negative energy anyway. For two objects infinitely far apart, the field energy is zero. Move them closer and let go: as they fall towards each other the field intensifies, exactly balancing the increase in kinetic energy between the two objects - so that field energy has to be negative. It is this change in the negative energy field which propagates as a wave. As the objects spiral in towards each other, the spiralling of the wave creates the characteristic ringdown "chirp". On merging, the positive kinetic energy is swallowed by the event horizon and converted into positive mass per e=mc2. This is balanced by the energy of the wave, which is is just the negative field energy released during the acceleration/spiralling phase. So yes the wave gains energy, but it is negative energy (analogous in this sense to "more electrons" meaning more negative electric charge), while the new hole's mass is actually greater by the sum of the two kinetic energies wrt the overall centre of mass.
There is surely also a trading-off of various energies among the hangers-on outside the event horizons, and that must include the gravitational field of the hole, the mass and magnetic field of the accretion disc, etc. etc. All in the context of frame-dragging. But if you understood all that you'd get a Nobel prize.
I cannot claim to be any kind of expert on black holes, but I can spot contradictions.
1) When two objects move towards each other, it is true that their potential energy decreases. As it happens, this energy tends to an upper limit as they move apart, so we simplify this limit as "0", which means that the value of PE for any system of physical objects is always negative. Which is entirely different then referring to "negative energy".
2) We have repeated observed that when black holes merge, they end with a mass deficit. In this case 15M☉. But we need to be specific. We start with 100M☉ inside event horizon A, and 140M☉ inside event horizon B. These event horizons then merge, ending with 225M☉. To be sure, part of what is happening is that the potential energy in the system is being reduced. Thanks to GR, we know that it is converted both into KE and mass. (And in this case, the amount of mass may be significant.) BUT..this only makes the problem worse, as we need even more mass to escape the system. Now the form of the energy is clearly the gravity waves, without which we would not be able to hear this event at all. This does not answer the problem of the mechanism, which is where the puzzle lies.
There are really only two possibilities. The first is Hawking radiation. You brush off this possibility, but depending on how you view Hawking radiation, it is possible that it is substantial, especially since the event horizons distort. The second is that there is another mechanism for energy to escape, namely gravity waves.
Although see e.g.
Electromagnetic Energy Extraction from Kerr Black Holes: Ab-Initio Calculations
Meringolo et al
The possibility of extracting energy from a rotating black hole via the Blandford-Znajek mechanism represents a cornerstone of relativistic astrophysics. We present general-relativistic collisionless kinetic simulations of Kerr black-hole magnetospheres covering a wide range in the black-hole spin. Considering a classical split-monopole magnetic field, we can reproduce with these ab-initio calculations the force-free electrodynamics of rotating black holes and measure the power of the jet launched as a function of the spin. The Blandford-Znajek luminosity we find is in very good agreement with analytic calculations and compatible with general-relativistic magnetohydrodynamics simulations via a simple rescaling. These results provide strong evidence of the robustness of the Blandford-Znajek mechanism and accurate estimates of the electromagnetic luminosity to be expected in those scenarios involving rotating black holes across the mass scale.
https://arxiv.org/abs/2507.08942
Ergo a colliding pair in the 50 - 100 SM range will result in in one of 100 - 200 SM range. We keep observing collisions. Nothing forbidden about any of that.
Sure. But if these collisions are frequent wouldn't we expect to see a continuous distribution of black hole masses: some in 100-200, a bit less in 200-400, less again in 400-800 etc?
Their mass distribution is stellar (Figure 3) and their ringdown truly sonorous (Figure 1)!
It's a gift from Nature (Ref. 1) ... the non-eccentric(?) BBH twerk contest between 137₋₁₇⁺²² M⊙ and 103₋₅₂⁺²⁰ M⊙ at the GW231123 dance hall ... well worth a gander!
-- Your friendly librarian
(you beat me to it harmjschoonhoven ... well done!)
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