The Final Parsec Problem: do SUPERMASSIVE black holes ever MERGE?

[@silkworm6861]

I did my PhD on the final parsec problem. It's mostly covered very well, but the most important part is probably around 8:45, that "our math isn't quite right". What is actually claimed is that the final parsec *problem* results from oversimplification of the physics ("a spherical cow"), and relatively quick mergers occur otherwise. This is pretty much the consensus today. Also, at 10:04 that's a picture of Rai Weiss, not Vladimir Braginsky.

[@mrpearson1230]

Actually, that is Vladimir.

[@luudest]

What about simulations? How the do they resolve the problem?

[@silkworm6861]

@@luudest Simulations like in this Berczik et al. paper show that if the surrounding Galaxy isn't a nearly perfect ball of stars (post-merger galaxies generally are pretty spherical), in other words, it is ellipsoidal or "triaxial", then the torques exerted by the galactic potential will lead stars to "centrophilic" orbits, which means they come close to the SMBH binary, interact with it and steal orbital energy and angular momentum, shrinking its orbit rather quickly. In a perfectly spherically symmetric stellar model (as is assumed in semianalytical calculations and early simulations) there are no such torques and the SMBH binary depletes the reservoir of stars that can interact with it by the time it gets to 1 parsec separation (this reservoir is called the "loss cone" and in this case, it is said to be in the empty regime). There are quite a few more processes (other than galactic torques) that can refill/"repopulate" this loss cone.

[@silkworm6861]

@@mrpearson1230 I can tell you with full certainty, it is not.

[@stevenchristenson2428]

I think that this is likely the reality of it. Math can get you pretty far in understanding the universe but I think sometimes researchers get lost along the way. Math is a great tool but its also no 100% representative of reality, and that's apparent from its paradoxes.

[@louisroberts4089]

When I did my Astrophysics degree (1990-93) we did some calculations on the effect of solar bodies in a distribution being influenced under their own gravity. I looked at sub clusters. The potential energy is twice the kinetic energy of the sub cluster falling in on itself. If you have 3-4 objects close to each other that they fall together and you will find that 2 of the bodies end up in a stable orbit and the 'extra' kinetic energy is taken from the system by the other bodies and those bodies ejected from the sub cluster leaving the remaining 2 bodies (generally) in orbit. This kind of explained why we see a lot of either single or binary systems (whether Steller or galactic) but not many tertiary. Now - if you use the same simple theory to black holes, you need extra heavy bodies to take away the kinetic energy to force the bodies together. In previous videos it was mentioned that there may be multiple black holes at the centre of a galaxy, so if we have multiple bodies, one of the bodies can be ejected taking away energy from the orbits and allowing the bodies to get closer together. A 'simple' system of just 2 black holes may take a long time to merge - but that an unusual situation as in general there are more bodies about that can collapse in and fly out of the sub cluster taking energy from the system.

[@captain_context9991]

Well thats just the 3-body problem, isnt it. The unpredictability of 3 big objects. Mostly the third one will be ejected and then youre left with a 2 body system. Which works fine. Same will mostly happen with a 4-body system.

[@Lord_and_Savior_Gay_Jesus]

LIsten, I have the answer to the Final Parsec Problem: Firstly, you'll need a flux capacitor with settings to read dynamic equilibriums of stellar kinematics. Then, attach this to a Maximogaster Occidentalis using USB 3.0. Don't use 2.0, it's inferior. Then, engage the parsec pneumatic distributor on the Maximogaster Occidentalis to identify Axioms within the Novapod Majordermis sector of pre-main sequence star evolution. Turn the ignition on, wait a half hour. Then, download the memory files from NASA's Pleiades Supercomputer and you'll have your answer.

[@KilgoreTroutAsf]

For times larger than the Lyapunov time of an N-body system the dynamics become chaotic, which means kinetic energy is exchanged between orbits and eventually some bodies may "evaporate" from the system, but there are some three-body configurations, namely S- and P- type orbits that can be metastable for long periods of time. As with anything chaos, it strongly depends on the initial configuration of the system.

[@Entropic0]

That doesn't solve the issue. The point is that the closer the black holes are together, the less likely they are to have an encounter with another body. Changing the type of body (from "star" to "black hole") ironically makes an interaction less likely to happen because black holes are very rare compared to stars. A theory that could explain the "final parsec problem" would be a theory that increases the probability of an interaction.

[@captain_context9991]

@@KilgoreTroutAsf I was pretty sure a 3 body system would sooner or later expel the third entity.

[@silo_fx3182]

This was so well explained. Wonderful presentation. You are amazing at translating these mind bending concepts to us 'normies'. Great stuff.

[@willstack6188]

What about Hawking Radiation? ( last parsec problem)

[@boathousejoed1126]

You do realize it's all theoretical.

[@oddjam]

100%

[@Mortonbmx]

​@@boathousejoed1126 judging by the fact they said "concepts" I'd take a wild guess and say yes...

[@IanWilliamsJericho]

@@willstack6188 I was wondering the same. I suppose supermassive blackholes would lose energy this way, but I guess it would take a very, very long time - much longer than the age of the universe...

[@donelson52]

Wow. What a time to be alive! For me, 1952 until now, amazing new knowledge EVERY DAY OF MY LIFE. In a universe capable of turning the atoms of dead stars into intelligent beings. Thank you, Dr B ❤️

[@qkcmnt1242]

Is it the UNIVERSE turning atoms into intelligent beings, or an eternal Creator, Who is doing so?

[@trxe420]

Man, I knew listening to physics every night for years before bed would pay off. I actually understood everything you said and even anticipated a few like LISA/PTA etc. You have a great way of explaining things.

[@neflarionshadowflame2050]

Since I was one of the people who said they'd like a video on this topic, I figured I'd say thank you for making it. I love learning new things, especially things about space and our understanding of the universe and how it all works, and I definitely learned something today.

[@Sean_neaS]

I just have to say the audio and video on this channel are absolutely perfect. So many channels are overblown when they upgrade equipment, but this is one is flawless.

[@allanlees299]

Wonderful exposition - simplifying a complex topic without distorting it - and carried along by seemingly boundless enthusiasm. What a marvelous way to present astrophysics. Thank you!

[@matthewjohns1758]

Wouldn’t one be more Super Massive than the other?

[@Darthsiroftardis]

Was really looking forward to this video, thank you for reading the comments and giving us the video we wanted!

[@bosstowndynamics5488]

"Pulsar timing array" sounds so badass as a name, it feels like we've built a galactic scale superstructure for detecting gravity waves. A fitting instrument for exploring supermassive black holes.

[@qkcmnt1242]

I keep thinking "galactic" has something to do with icebergs for some reason. 😅

[@qkcmnt1242]

.. maybe I'm seeing "arctic" somehow in it. 🎉

[@ucantSQ]

SMBHs flinging each other into the void reminds me of evaporative cooling. The higher energy particles escape the system, leaving lower and lower energy particles behind. In the case of the Einstein-Bose condensate, the remaining particles eventually get so low in energy, they collapse in on themselves and occupy the same quantum state.

[@drunta]

So much work into making this content so very approachable. So much skill by Dr. Becky Smethurst (and clearly her team of hundreds) to create it. And shout out to the University of Oxford to carving out bandwidth for Dr. Becky to communicate to the masses when I know she has research, publishing and teaching obligations.

[@chrishunter9294]

Wouldn’t hawking radiation cause for a loss of momentum between the black holes and thus an eventual merger?

[@Amethyst_Friend]

@@chrishunter9294They lose energy through GW far, far faster.

[@Brian-L]

Every time Dr. Becky said “The Final Parsec,” I played the Europe anthem in my mind too. We were on the same wavelength for this episode. 😂

[@CHSubZero]

This was a VERY interesting video. Thanks Becky! I NEVER thought about this final parsec problem....

[@dylannovak9728]

I love how you are adding pictures of the authors for papers now. So cool to get a glimpse and help us remember names in the long run!

[@MikeJamesMedia]

I'm not a physicist, so I appreciate that you can share things like this in such a way that I have a tiny bit of understanding of what you're speaking about. :)

[@silmarian]

So, basically, we’re either wrong or we’re wrong and we’ll find out in 14 years? I unironically love this.

[@vigilantcosmicpenguin8721]

Science is a very lucrative field because every time you solve a problem there's a new problem to solve.

[@timothyodonnell8591]

If LISA picks up no GW signals, the problem will be figuring out the source(s) that are producing the background GW that the pulsar timing array detected.

[@BorisKashirin]

When objects interact they exchange energy in such way as for all objects have same energy (actually not same, there is specific distribution, it is just usual temperature but applied to stars). Energy is basically orbit radius*mass (again not quite, but good enough for general picture). So if SMB and ordinary star have same energy SMB will have much smaller orbit. I think this picture helps with understanding how SMB ends up in the centre of the galaxy.

[@matthewjohns1758]

Sorta.

[@sethseymour2917]

WE'RE IN A BLACK HOLE, MAN! 👍

[@stephanemandelert4321]

Dear Dr. Becky, I would like to express my gratitude for your KZbin channel. We have an observatory oriented to the public here in Granada and you help us a lot to keep updated on the subject. My only sadness being to discover that you passed by here a couple of month ago and we weren’t at the airport with a poster commemorating your venue as the superstar you are! Let’s hope the next time we will know in order you get the reception that you deserve 🤗

[@rickgotner7596]

Considering the time dilation effect grows the closer you get to the event horizon of any black hole, I'm afraid I'm at a loss how from an external perspective, any merger ever occurs in less than an infinite amount of time. I understand we currently think they do, but how is time dilation overcome?

[@Solnoric]

The dilation is relative. For the black holes, it takes a nigh-infinite amount of time. External viewers see time pass differently.

[@iridescentsquids]

@@SolnoricWhich means that from the merging black hole perspective our time appears to race infinitely into the future…and from our perspective, no merger has occurred.

[@a.westenholz4032]

Or maybe our understanding of time is still flawed somewhere. It works for every day use, and even for much of the scientific theoretical use we currently have for it, but if every now and then we run into an impossible contradictions as to the nature of time according to our understanding then the logical conclusion is our understanding is wrong somewhere. I think we have a real difficulty imagining a truly timeless space, a place that exists outside of a timeline, where time is not a factor. I know black holes are supposed to be such places at their core, but if they were NOTHING would happen or change- it would be static and frozen. For things to change takes the aspect of time. Even non-linear time of some sort would do. So even at their core, if change is possible, time must still happen in some form or another, even if completely different from what we know. I don't think there is any part of our universe that is without time, even black holes, as it is fundamental to it. Time may be more changeable and fluid than we currently understand, yet also more rigid (I have a theory that time travel is only possible one way, i.e. to short cut ahead, but not in reverse due to the directional flow of time in the very fabric of the universe- which is why we'll never find any incidents of time travelers from the future). IDK- but I have always thought that past the event horizon the laws of physics get so warped and changed that we have little chance to really know what they are, at least not currently. The same goes for time. But it doesn't mean it isn't there.

[@yallimsorry5983]

@@a.westenholz4032 I get your reasoning but remember it’s general *relativity* for a reason, if you were able to fall into a black hole, time essentially passes normally for you, it’s the perspective of outside observers seeing your clock that becomes frozen. Your view of the outside universe also becomes radically different, as all the light that’s ever entered the black hole concentrates into a smaller and smaller point. Past the event horizon our best idea is that time and space flip, since all future movements are towards the singularity, space itself becomes a one way arrow or ‘time-like’ and time becomes “space-like” since moving through it is physically moving you towards the singularity. It’s the singularity itself that’s the problem, not time dilation, which we know exists.

[@yallimsorry5983]

@@a.westenholz4032look up Penrose diagrams if you’re interested in this topic, I’m not a physicist in any regard but that’s my best lay understanding. General Relativity is essentially the best tested theory in all of science, and we still haven’t found anything that disproves it, we just know it’s incomplete since we can’t work out what happens at the Big Bang or at the apparently infinite density of black holes, but the Penrose Diagram definitely helps explain the interiors past the event horizon.

[@Kevin-t6n4d]

Luv your wide-eyed enthusiasm for knowledge the fact that you don't hold on theories if you find new evidence that disagrees with past assumptions

[@Jondiceful]

As one of the viewers who requested this episode, thank you!! You made it make sense to me despite me not being a physicist or an astronomer. It certainly will be exciting when we solve this mystery.

[@hybridwolf66]

The way you make things easy for the lay-person to understand is why I am here. The bloopers and your beauty, make me listen. TY DR. Becky!

[@Caier127]

Love your videos they are so entertaining even though I am only 13 great job explaining all the concepts. Not many people explain stuff in this much detail.😊

[@DrDeuteron]

13 is a good age to start studying harder math than what school excepts…..it will help a lot when you’re an astrophysicist.

[@Caier127]

​@@DrDeuteron Thank You for the advice

[@billgaudette5524]

What the? I literally woke up this morning wondering what the deal was about the Final Parsec. I'm not even joking, lol! So glad to see this, you saved my day ⚡

[@eljcd]

Thank you kindly, Dr. ! I have been curious about this problem for a while, and you have addressed most of my doubts. Again, thank you.

[@frederickwoof5785]

Very intriguing. They must have very complex calculations. Those smbh's must have a whole lot gas, stars and black holes following in their wake.

[@StereoSpace]

This reminds me of Zeno's Achilles paradox. You get so caught in the semantics of your mathematical definitions that it no longer describes reality. Very similar as well to a famous bit of calculus called Gabriel's Horn.

[@vhulheim]

Finally, I can't believe you made us wait SO LONG for this video.

[@l3ete1geuse]

I never get tried of watching your videos, Dr. Becky.

[@EebstertheGreat]

1:14 Looking at a screenshot of a creator's KZbin channel with 2 notifications is so satisfying. I always shed a small tear when I see the 99+ there, knowing they probably have thousands of notifications that they can't hope to check.

[@pascalbro7524]

This was a phenomenal presentation tying a bow on everything that's been happening. Thanks Dr.

[@v2o3]

Thanks Becky! Haven't watched your content in a while but seeing this makes me want to watch more of your videos again. Keep up the good work!

[@Earwaxfire909]

You are a very inspiring explainer of science! I wish we could all learn to teach this well!

[@Alacritous]

To us, observing from outside they do. But to them, time dilation makes it look like it takes until the end of the universe

[@joshuahillerup4290]

What about other black holes that aren't as massive as the central supermassive black holes, but massive enough that dynamical friction causes them to fall to the centre of the galaxy, and then getting slingshotted out themselves?

[@Lonewanderer30]

It's very obvious. We don't understand near as much as we like to think we do, especially theoretical physicists. The final 'parsec' problem, is in fact simply hubris.

[@bitmau5]

The final parsec problem is only an issue for those who are trying to make their ship do the Kessel run in less than twelve parsecs!

[@michaelfried3123]

yeah, comment of the day! seems like most of physics is sci-fi and not real science doesn't it?

[@bitmau5]

Not at all, I just couldn't resist the meme, because back in the day, it was Sci-Fi that got it wrong, not the other way around '-)@@michaelfried3123

[@DarkVoidIII]

I have some observations: 1. Gravitational waves from black holes suck in all particles around them, thus meaning that the clouds of gas are being absorbed by the black holes as it gets close enough to them. This means that they're slowly accreting matter as they spin around each other and through these clouds. Even light being emitted from these clouds that falls onto the black hole can be considered to be a small contribution to it's mass. 2. If one black hole is even slightly smaller than the other black hole, the larger black hole will start feeding off the smaller black hole. This is due to immense gravitational waves that cause the black hole to suck everything around it into itself. If the smaller black hole can't gain enough matter through accretion, it will eventually become a part of the larger black hole through accretion and through loss of matter. 3. Since both black holes are spinning, this means there is a force that started that spinning motion. Some amount of this force might have come from the black holes themselves. If there are external forces that caused the spinning motion, the laws of motion come into play. When the motion is sufficient, it will cause both black holes to merge. If it is insufficient, it might cause them to spin around each other. We are witnessing spinning in our own lifetime, but it could take longer than the age of the current universe to notice enough motion for supermassive black holes to merge together. That's just the timescale they operate on.

[@samhainsknight7295]

Astronomy is so amazing and facinating! Your videos do a great job of explaining everything..always love to learn new things every week!

[@SoulisStar]

“Rude”. I love it. It’s been a while sense I’ve heard it used like that. Brilliant. Thanks for being awesome.

[@PhonicallyPsychotic]

This might be a silly question but what happens to time dilation as black holes get closer? Also, since anything that touches or crosses over the event horizon is trapped are we detecting the merger or the instant before the merger, and as an aside: does gravitational lensing effect what we "see" ? Would a singularity generate a lense around itself ? Sorry if these have been asked and answered before. Cheers :)

[@leonmusk1040]

I know I honestly think dilation is one of the most ignored things in astrophysics. Having time dilation affect gps merely by escaping Earth's pathetic gravity well would suggest the weight of the sun jupiter the galactic arm and smbh at the middle how much of what we see is actually stretched thin by the well.

[@EnglishMike]

That's a different issue to the final parsec problem which starts when the two SMBH's are around three light years apart. At that distance time dilation just isn't an issue. You could happily live out your life on a planet within 100 AU (0.00158125 light years) from a super massive black hole (assuming there's no radiation that can kill you).

[@sitrilko]

I just like you've started adding portraits of the scientists! It really helps to remember them, because you now have a face to associate, not just some random name.

[@js70371]

Dr. Becky you’ve been putting out some great content as of late! And once again, I cannot praise you enough for these medium length videos. I find 15 mins to be just about perfect for most topics I take interest in, which is quite varied. Thanks for another good one! Also, big kudos for your “bloopers section” of your videos that you’re adding now. It gives us, your fans and supporters the chance to see your wonderful sense of humour and to somewhat take you off the pedestal of “scientific superstardom” for a moment and show us that you’re just human after all, like the rest of us “mere mortals”!! Lol 💫🙏❤️😂🍻

[@gkelly34]

I believe SMBH’s spontaneously appear within the centre of gravity of a galaxy in its early formation where the whole galaxies mass pinches space-time right at the centre

[@starwave8228]

My little brain gets so overwhelmed with Space stuff. i think Merging could be Flexible, Some Supermassive Black Holes Merge & Some don't, it just depends on the how the first date goes... I'm just gonna imagine it would be like adding Milk in my Tea, If they Merged.

[@peterlip8]

Another great vid, thanks. When mentioning LIGO & Virgo, don't leave out the new kid on the block, KAGRA, which is based in Japan. It's just finished it's second observation run, and plans to fire up again next year.

[@DavidvanDeijk]

great episode, love learning the details of this problem

[@zriraum]

She's back ya'll. Gonna save this for later.

[@Valdagast]

In fact, if you slingshot around the Sun while traveling at high warp, you will travel back in time. 5:56 So dark matter interacts via gravity. Does this mean that the black holes also clear the galaxy center of dark matter?

[@johannageisel5390]

AFAIK dark matter is bad at cooling, which protects it a little bit from falling into black holes. In a normal accretion disk the matter heats up a lot by friction and then radiates the energy outwards as light of various wavelengths. Thus it loses its kinetic energy and finally falls into the BH. But dark matter cannot radiate light, so it cannot use this way of losing kinetic energy. That's also why the DM halos of galaxies are spherical even when the galaxy is disc-shaped. Now, when you have TWO black holes and not only one, it gets interesting. Those should be able to slingshot dark matter outwards. But there is another phenomenon that I have seen a while ago on a picture. There has been an analysis of the Bullet Cluster and they figured out that the dark matter got separated from the baryonic matter during the merger. It fell out of the galaxies, so to speak. I have no idea how that would now interact with two SBHs orbiting each other. On the picture, the dark matter seemed to have clumped into a single halo pretty quickly while the baryonic matter masses fell through each other and came out on the other side, having been stripped of their DM halos. Therefor one would assume that the black holes also fell past each other but did not do much with the dark matter. I wish I knew more about these things, but I can only report what I've seen on that picture.

[@robertbryner3414]

I saw a documentary about this. I think it was called Star Trek IV.

[@DrDeuteron]

@@robertbryner3414isn’t there an earlier one with Teri Garr?

[@toomanylies7716]

Just binged 3 or 4 of your vids. I think I need to start at the beginning. I love the info and the delivery.

[@johannageisel5390]

I have a question: We know that our Milky Way has swallowed a couple of dwarf galaxies over time. What happened to their central black holes? Did they not have one?

[@Alex-dh2cx]

Possibly not, or possibly just floating around the disc. There's one Galaxy without a black hole that JWST spotted.

[@davehart9972]

there is no such thing as black holes. its all BS

[@Alex-dh2cx]

@@davehart9972 so sayeth Dave, some guy on the internet.

[@davehart9972]

prove me wrong, wont happen face it, its a giant $cam. @@Alex-dh2cx

[@PauxloE]

If I understand it right, in a galaxy with two super-massive black holes in the one-parsec distance, these would normally not be active as they've slung out or eaten most material nearby, and also without any nearby stars? So it would be somewhat difficult to observe them, except by an absense of fast-moving stars in the middle of a galaxy.

[@RobRutherford]

I was thinking about the swarm of smaller black holes that sink into the galactic core, but I'm guessing they aren't a enough of a contribution to be significant otherwise they would have been mentioned.

[@steffenbendel6031]

Only the relatively heavy objects should sink due to (dynamical) friction. Stelar black holes are lighter than the original stars.

[@willbarnstead3194]

@@steffenbendel6031yeah, but there is evidence now from LIGO for frequent black hole mergers creating black holes with dozens of solar masses. I wonder if the maths have taken this into consideration.

[@kenashworth7672]

@@steffenbendel6031 Would it be possible for those stellar black holes to merge until the resultant merged black holes are massive enough to sink?

[@KuK137]

@@kenashworth7672 Not really, these things are tiny and a merger would require two of them hitting head on (or somehow start orbiting each other long enough to merge). The chances for that are astronomically small, it's like trying to hit grain of sand with another grain of sand thrown from several kilometers away. Which BTW leads to another black hole problem, namely how supermassive black holes arose in the first place because stellar black holes grow way too slow over universal lifetime for it to be normally possible...

[@steffenbendel6031]

@@KuK137 I guess whole regions of space collapsed in the early universe to for the big black holes. Might be easier with a lot of black matter instead of normal one. On one hand, it can not lose energy by radiating, but probably also not resting the collapse like normal stars. And there probably was not enough time for a slow evolution anyway.

[@MegaFortinbras]

How would one tell the difference between a merged supermassive black hole pair and a pair in orbit only a parsec apart?

[@DrDeuteron]

By counting the total number of black holes?

[@MegaFortinbras]

@DrDeuteron Let's say that a galaxy with two supermassive black holes is 32.5 million lightyears away. How can you tell if there is one back hole or two that are separated by one parsec, which is one ten thousandth of a percent of the distance?

[@jamescomstock7299]

Actually, isn't there another problem with the mechanics for the creation of supermassive black holes if they never merge?

[@DrDeuteron]

Does antigravity mean negative energy? I mean we have repulsive forces, and they don’t make negative rest energy.

[@chriscrow8774]

another fun research about black holes is the low mass gap between neutron stars and low mass bhs (~2-5 solar masses)

[@louisalfieri3187]

Thank you. So good. What makes us think supermassive binaries have stable orbits?

[@alexanderskorniakov5037]

What I can't get through in these matters is that besides this final parsec problem we have time slowdown in an extreme BH gravitation field for an external observer. That is, two BHs should not ever fully merge as it mathematically should take infinite time...

[@EnglishMike]

That's only a possible problem if the black holes are nearly touching. We can see stars orbiting our galaxy's SMBH as close as 100AU and there's no observable slowdown their orbits, so nothing extreme is going on in that final parsec regarding time dilation. You could be right, but it's not the solution to the final parsec problem.

[@renesoucy3444]

What if any black holes really merge and are still furiously orbiting each other under the event horizon?

[@leonmusk1040]

There would be no difference once it falls below the event horizon the information is lost. It could take billions of relative years for said object to merge but it would have happened the moment it slipped below the event horizon to external observers in non dilate space. That is what dilation is we're currently in dilated space and experience a colour shift slash clocking discrepancy just between us on the ground and the satellites giving dilation corrected gps locations gps mk1 failed as there was no timing compensation.

[@renesoucy3444]

For me it’s a paradox that the rotational speed of a collapsing star core becoming a singularity can go over the speed of light well before it becomes a singularity, it seems wrong to me but I’m no physicist, but for me, that’s impossible, kinetic energy will equate the gravity power because of E=mc squared, imo.

[@qkcmnt1242]

Dr Becky Smethurst is my favorite astronomy channel. There are others I watch, which I like as well, but the second behind her has a Eurasian brogue that's difficult for me to readily decipher. Anyway, thank you, Dr Becky, for also making astronomy fun with your bloopers.

[@spheresong]

When the SMBHs fling the stuff away, is it hard enough for the galaxy to lose the stuff or will it fall back in to sap more energy?

[@olafschluter706]

As a physicist I am so happy that videos like this are so popular on YT. Reassures me of people still being interested in science despite all the bullshit that is posted on the internet about politically (not scientifically) controversial topics like climate change.

[@kiks138]

Great Video, Dr.Becky! I'm currently reading A Brief History of Time by Stephen Hawking, and I'm currently on the chapter of Black Holes. This has surely helped me! Thank youu :)

[@hanssteyn9775]

Thank you. Always a pleasure listening to smart people.

[@rwarren58]

Thank you for the data regarding Project Lisa. The continuing brilliance of our Astrophysicists is nothing less than astounding. As to whether the black holes merge, it sounds like a job for JWST. Our time machine see everything.

[@qkcmnt1242]

I enjoyed your 4:05 fling affect videography, expressing what you were talking about. That was keen. 😊

[@Baughbe]

Just a thought, but as I studied turbulence in aerospace, could there be a similar effect in between orbiting SBHs? Causing turbulence in space itself from the high gravitation? That would add another factor that would take energy out of the system.

[@Charliethephysicist]

Can you be more specific? Turbulence or not, you have to have energy carried away by something. If there is no significant gravitational wave, whether turbulent or lamina, generated to carry the energy away, there is no energy dissipation.

[@dichebach]

I love when scientists accept that they might be wrong and get excited about that. It is the BEST part of science, and it should be every scientists duty to teach it as passionately as you have here!

[@jeremyelser8957]

Binary black holes make gravitational waves, which seem like they take a lot of energy to make. That energy has to come from somewhere, so wouldn't it come from the orbital energy of the binary pair? Would that radiate away enough energy to let the black holes merge?

[@RodrigoLobosChile]

Wow... this video really blew my mind.... Many thanks for taking the time to create a simple explanation.

[@cmuller1441]

Couldn't those supermassive blackholes be actually a swarm of smaller ones on the verge of merger. Too many and too close such that from far away it's indistinguishable from a single supermassive one?

[@stargazer7644]

"swarms" of blackholes would not be stable.

[@andersjjensen]

Generally three body systems kick out one and form a binary unless one of them is so much bigger than the rest that it becomes "a planetary system".

[@1dgram]

When you mentioned the final parsec a few weeks ago, I had "🎵The Final Parsec🎵" stuck in my head too. You're not the only weird one. 😀

[@klauschristensen5845]

Would it be trivial for an astronomer to tell, if there’s a single massive black hole in a galaxy center or there are two orbiting a parsec apart?

[@michaelsommers2356]

I'm not certain, but I think it would depend greatly on the distance of the galaxy. It would be harder to tell the difference the farther the galaxy.

[@d_andrews]

The image of the black hole at the centre of our galaxy from last year puts the black hole's shadow at about 3.2 light minutes, i.e. well below a parsec, so we can be quite confident in that case at least :) For some very distant galaxies it might be harder to tell

[@qkcmnt1242]

I think two orbiting, spinning black holes, totally infatuated with one another, in the act of absorbing each other, would be on the final phase of galaxic merger, such that for all practical purposes, there's but one galaxy, DESPITE the "orbitation" relative both black holes. We're talking LOTS of time, though, perhaps billions of years, to get to this phase.

[@qkcmnt1242]

I don't think it would be trivial, but difficult, especially the ginormous distance from whence we have to observe it.

[@52flyingbicycles]

I have a few theories 1) if you include the high initial velocity of black hole mergers, it’s possible their co-orbits are highly eccentric and that could push them below the rapid merger threshold more quickly than two SMBHs passing in the night 2) there is a survivor bias of 1 and 2 black hole galaxies. If a third galaxy tries to merge, it gets flung out as a 1 hole galaxy and the other 2 merge as a 1 hole galaxy. But this process is very quick so we may not see much of it, or might not recognize it if we see it. Suddenly throwing the third SMBH out of the system might not take many stars with it, making it hard to spot. 3) I saw a comment that said the final parsec problem might just be a result of the math being too simplified. 4) though there may not be many stars near them, the stretching and pulling from the hundreds of billions of stars in their galaxies could be enough to push them closer. Especially if the SMBHs have eccentric orbits. 5) dark energy

[@jonathankennedy2888]

Hey Becky, I love your videos. I know black holes can get massive, but how small can they get?

[@danmurray1143]

Well, with dieting & proper exercise...

[@ptonpc]

It feels like the boundaries of knowledge are being pushed back faster than before.

[@silliconcarbon6637]

Question! Wouldn’t two black holes both lose energy by rotating around each other (after they’ve cleared everything around them? If so, wouldn’t that bring them closer and closer together?

[@itcamefromthedeep]

Yes. Very slowly. The reason the merger takes longer than the age of the universe is that the effect is quite small at ~3ly. If not for that effect, they would never merge at all and just continue in orbit around each other indefinitely.

[@Mach101010]

"🎵it's the final parsec🎵" You are a nerd of cosmic proportions. Keep it up ✊❤️

[@jennifersaar1611]

Would dwarf galaxies facilitate a merger? In many of the galactic mergers I'm seeing in the JWST images, there are numerous smaller dwarf galaxies dipping in and out of the galactic disks, leaving streamers behind as they gradually get pulled in. They would have much smaller central black holes, but perhaps they would be just big enough to throw things out of whack.

[@pauly362]

Good question!

[@jonbondy]

The graph you reference, showing the relationship between inter-black-hole distance vs time, begs to be expanded so that there is a 3rd dimension, resulting in a 3D sheet. The missing dimension is the size of the black holes. Clearly we believe that small black holes can merge and larger ones cannot. Seeing the relationship between black hole size and the other two variables would be very interesting.

[@synchro-dentally1965]

Wouldn't there be a difference in expansion rate of space due to GR and cause a net "squeeze" resulting in the black holes to merge?

[@qkcmnt1242]

Is GR Gamma Ray, or General Relativity, in your question ❓

[@qkcmnt1242]

Gravitational Resistance?

[@fratercontenduntocculta8161]

My favorite part of Astrophysics is how our universe is seemingly created with the express purpose of defying our understanding. A predictable universe would be both boring and essentially frightening.

[@connorm3436]

Would dark matter contribute to dynamical friction?

[@michaelfried3123]

dark matter is a myth, its not prove able science.

[@timothyodonnell8591]

I wondered the same thing.

[@JubeiKibagamiFez]

This is very interesting, because I always assumed that galaxies and galaxy centric super massive black holes were mostly stationary, but this finale parsec problem presents the possiblity that there are masses substantially larger than super massive black holes effecting the movements of entirely galaxies to the point where galaxies could collide with each other in the first place to even reach the Final Parsec Problem.

[@qkcmnt1242]

More mind boggling!

[@Sableagle]

They're father than Venus, and still rather small, but science's genius says they won't merge at all. It's the Final Parsec. 🎵

[@dyson9422]

If LISA is expected to launch in 2037, It will turn out to be an intra - generaational project taking 40 to 50 years which is nice to know but will need to compete for funding for more pressing problems like global warming.

[@ContrapuntalComposer]

I was just thinking... as an admitted non-astrophysicist... that maybe black holes could experience tidal deformation and so become ellipsoid as they orbit each other. Then, their elliptical event horizons could overlap and so allow the merger to finally happen. Just a guess! But here's a related question: I picked up somewhere that black holes are usually rotating... so how would the phenomena that I speculate be affected by the alignment or mis-alignment of the planes and directions of rotation?

[@greganderson1681]

Perfect explanations. I understand enough physics to keep up without getting sweaty. Just don’t ask me about the maths!

[@Mataclysm]

I have three threads of questions. 1) Will two SMBHs end up in the orbit you described regardless of their original paths and velocities? What would happen if, as unlikely as it is, they were on course for a direct head-on collision? 2) Would their spins and accretion disks being in opposition change the equation at all? 3) If two SMBHs merged, the gravitational wavelength would shorten over time as they spiral in and accelerate, right? Would the amplitude of the waves still be too huge for even the pulsar timing array?

[@joegee2815]

Great, I held out to the end and got "The Final Parsec" song stuck in my head now.

[@allenaxp6259]

It is also possible that the discrepancy is not a problem at all. It is possible that the current understanding of physics is correct, and that supermassive black holes never merge. However, this would mean that we have to rethink our understanding of how galaxies evolve.

[@EnglishMike]

That's basically what she said in the video.

[@allenaxp6259]

@@EnglishMike Yes that is correct, however it is still not clear which, if any, of these solutions is correct. However, the final parsec problem is an important one to solve, as it has implications for our understanding of galaxy evolution and the formation of supermassive black holes.

[@krumplethemal8831]

Black Hole 1: "Hey you should merge with me.." Black Hole 2: "No I think you should join me instead." Black Hole 1: "If we don't merge it will drive humans crazy.." Black Hole 2: "Who cares about humans? But if you are concerned, you can just join me.." Black Hole 3: "Hey guys, can I join you?" Black Hole 1: "I think we might need a lawyer.."

[@geoffstrickler]

Chandrasekhar’s math is based on non-rotating black holes. Given that all known black holes rotate, there will be energy loss from rotation (and the associated space-time dragging and the gravitational waves that produces).

[@willfreese]

If relativity tells us that the event horizon is the point at which, from an outside observer's frame of reference, no further events take place for the thing falling into the black hole because that falling object's clock stops, how would black holes merge anyway? From the point of view of the black holes, they fall into each other while our clocks run to infinity, but from our viewpoint, they stop when their event horizons touch. I am sure this must be wrong, but I need it explained to me in a way that I can understand, and you are good at that sort of thing.

[@afaegfsgsdef]

I'm not a math surgeon, but I would expect them to have a lot of drag effects on each other and the stars/gas orbiting them.

[@stargazer7644]

Drag from what?

[@edwardhendry2179]

Thanks so much for your explanations.

[@TheYorkRose]

This makes a lot of sense, and I didn't know the details before. I guess two supermassive black holes in a binary setup generally acts like one double sized one if it's all totally stable, and in any real situation they're not acting in isolation because there are thousands of stars and particle clouds and other objects that are also disrupting the final parsec? But looking forward to those results telling us what's what! I love that our understanding is always improving and being challenged - the cutting edge of real science 😊

[@henrychoy2764]

simple suggestion why two supermassive black holes that get within parsec range will be hard to keep apart for long - the two super massive black holes are not likely to spin with parallel axes so they are likely to interact with more than just gravity and thus move in ways that interact with the electromagnetics of the galaxy - and quite a few of the so called ejected things are actually just sent into very long orbits - not to mention that distant things are always on their way to cross paths with these black holes