# What came first, the galaxy or the black hole? JWST tackles astrophysics’s “chicken or egg” question ## Метаданные - **Канал:** Dr. Becky - **YouTube:** https://www.youtube.com/watch?v=B9yDWbilIG4 - **Дата:** 07.08.2025 - **Длительность:** 15:01 - **Просмотры:** 188,483 ## Описание AD - To try everything Brilliant has to offer for free for a full 30 days, visit https://brilliant.org/DrBecky and you'll also get 20% off an annual premium subscription. | Just like in biology, astrophysics has its own “what came first, the chicken or the egg?” question. In this case it’s “what came first, the galaxy or the supermassive black hole?” Because as we look at the Universe around us today we find that at the centre of every galaxy is a supermassive black hole, and what’s more is that how heavy a black hole is, is tied to how heavy its galaxy is. The two are correlated. So we interpret that as galaxies and their black holes growing together, evolving together. If you grow one, you grow the other, along that correlation line. But if we think about what would happen if we rewound time, back to the early days of the universe when stars were just beginning to form, did the black hole form first, and then the galaxy of stars form around it? Or did a galaxy of stars form first, one of them die and go supernova and become the central black hole? To work that out we have to look back in time, because light takes time to travel to us, as we look at more distant objects the light has taken longer to get to us and we’re seeing them as they were billions of years ago. So the further back we look, the further we rewind time and get closer to answering that question of chicken or the egg; galaxy or black hole. Thankfully, we now have the James Webb Space Telescope, that has been designed to detect the faint light from very distant objects, and since its launch in 2021 there have been high hopes JWST would help crack this age old question... Geris et al. (2025) - https://arxiv.org/pdf/2506.22147 van Dokkum et al. (2025) - https://iopscience.iop.org/article/10.3847/2041-8213/addcfe Agarwal et al. (2016) - https://arxiv.org/pdf/1510.01733 Bowler et al. (2017) - https://arxiv.org/pdf/1609.00727 Bogdan et al. (2024) - https://arxiv.org/pdf/2305.15458 Harikane et al. (2023) - https://arxiv.org/pdf/2303.11946 Maiolino et al. (2024) - https://arxiv.org/pdf/2308.01230 00:00 Introduction 03:45 Paper 1: The lowest mass supermassive black holes spotted with JWST 09:03 Paper 2: A direct collapse black hole with JWST? 13:50 Which came first: the galaxy or the supermassive black hole? 14:14 Bloopers --- 📚 My new book, "A Brief History of Black Holes", out NOW in hardback, paperback, e-book and audiobook (which I narrated myself!): http://lnk.to/DrBecky --- 👕 My new merch, including JWST designs, are available here (with worldwide shipping!): https://dr-becky.teemill.com/ --- 🎧 Royal Astronomical Society Podcast that I co-host: podfollow.com/supermassive --- 🔔 Don't forget to subscribe and click the little bell icon to be notified when I post a new video! --- 👩🏽‍💻 I'm Dr. Becky Smethurst, an astrophysicist at the University of Oxford (Christ Church). I love making videos about science with an unnatural level of enthusiasm. I like to focus on how we know things, not just what we know. And especially, the things we still don't know. If you've ever wondered about something in space and couldn't find an answer online - you can ask me! My day job is to do research into how supermassive black holes can affect the galaxies that they live in. In particular, I look at whether the energy output from the disk of material orbiting around a growing supermassive black hole can stop a galaxy from forming stars. http://drbecky.uk.com ## Содержание ### [0:00](https://www.youtube.com/watch?v=B9yDWbilIG4) Introduction You know how biology has that iconic question, what came first, the chicken or the egg? Well, ash physics kind of has its own chicken or egg question, but instead it's what came first, the galaxy or the super massive black hole? Because as we look at the universe around us today, we find that at the center of every galaxy is a super massive black hole. And what's more is that how heavy that black hole is tied to how heavy its galaxy is. The two are correlated. So we interpret that as galaxies and black holes grow together. They evolve together. If you grow one, you grow the other along that correlation line. But if we think about what would happen if we rewind time back to the early days of the universe when stars were just beginning to form. Did the black hole form first and then the galaxy of stars form around it? Or did first and then one of those stars run out of fuel, go supernova and form a black hole which then sunk to the center of the galaxy and from there the two started to grow. To work that out, we can actually look back in time because light takes time to travel to us. And so, as we look at more distant objects, the light has taken longer to get to us. And we're seeing them as they were billions of years ago. So, the further back we look, the further we can rewind time, and the closer we get to answering that chicken or the egg question, what came first, the galaxy or the black hole? Thankfully, we now have the James Web Space Telescope that has been designed to detect the very faint light from very distant objects. And since its launch in 2021, there have been high hopes that JWST would help us crack this problem. And finally, in the past month, there have been two papers published that together are giving us evidence that favors the idea that the came first. So in this video, we're going to dive into these two JST papers. One from Garrison and collaborators and one from Van Dam and collaborators. But first, if you dream of becoming a scientist one day, maybe working with Jris Ty self one day, then like all scientists who came before you, you have to start with the basics and then work your way up from there. But if you're not sure where to start, then perhaps the sponsor of this week's video can help. Brilliant. Brilliant helps you get smarter every day with thousands of interactive lessons in maths, science, programming, data analysis, and AI. It's a learning app designed to be uniquely effective with each lesson filled with hands-on problem solving that lets you play around with concepts. A method that's proven to be six times more effective than just passively watching lecture videos. Brilliant's first principles approach helps you build understanding from the ground up. And it's that perfect mix of engaging problems, competitive features, and daily encouragement that keeps you motivated and on track. I love Brilliant Science courses. They help you make sense of the universe at every level. From the mechanics of simple machines all the way to the mindbending physics of black holes. With Brilliant, you can develop your scientific intuition through visual interactive problem solving that gets you hands-on with these key concepts. So, to try everything that Brilliant has to offer for free for a full 30 days, head to brilliant. org/dbecky or you can scan the QR code on screen or click on that link in the video description below and you'll also get 20% off an annual premium subscription. So, a big thanks to Brilliant for sponsoring this video. And now, let's dive into the first of these two papers that have been published this month. And ### [3:45](https://www.youtube.com/watch?v=B9yDWbilIG4&t=225s) Paper 1: The lowest mass supermassive black holes spotted with JWST let's start with this paper from Garrison Collaborators. Now, this paper appeared online in the past month and immediately caught my eye because yes, of course, people have been trying to find growing super massive black holes in the early universe with JBST, taking advantage of the fact that as gas gets pulled towards a black hole and starts to orbit it, the gas gets accelerated to huge speeds by the black hole strong gravity, giving it enough energy to glow so that we can see it. It's so bright that gas even billions of light years away. Sometimes it outshines entire galaxies of stars and that's how we know that the black hole is there and it's growing. But that means we can be a little bit biased when it comes to which super massive black holes we end up spotting at higher and higher distances because we're only going to spot the brightest ones. You know, the fainter ones aren't going to get lost in the noise and the brighter ones are the more energetic ones because, you know, they have stronger gravity because they're heavier. So, the first super massive black holes spotted with JWST were on the very heavy side, even for super massive black holes. In fact, they were over massive, more massive than we'd expect them to be given how little time they've had to grow to get to that point cuz we're seeing them as the universe was only a few hundred million years old. Here they are again on that plot we saw before with that correlation of galaxy mass in stars and black hole mass. They're well above that correlation line. they don't lie on the correlation line right down in the bottom lefthand corner like we'd expect from rewinding time if these things grow together. Now you could argue that this is just due to you know natural scatter around that correlation line. Like it's not a perfect correlation. There is some scatter and so if you're biased to only seeing the heaviest of black holes, the brightest of objects, then you're going to probe the extremes of that scatter. Or it could be that we're finally learning something about how galaxies and black holes grow and which came first. So Gears and collaborators specifically went looking for lower luminosity, so fainter growing black holes to try and find the lower mass black holes that we're usually biased against because they're so faint because they're so far away. They did that by stacking the light from around 600 galaxies that were spotted by JWST to reveal the collective signature of these lower mass black holes that we otherwise would have missed. Now, that means that you only get one measurement of the average black hole mass across all 600 of these galaxies rather than 600 individual black hole mass measurements. But it at least help us to understand if what we've been seeing with JWST before are the extremes of the scatters are the weirdos or is that actually the norm for the early universe and is that telling us something about how galaxies and black holes grow together. So here's what Gears and Collaborators have found. Again, it's this correlation plot, but it's very busy. So let's go through it piece by piece. The pink triangles are nearby growing super massive black holes right in the local universe existing after billions of years of evolution. The two colored lines are the typical correlation lines fit for those galaxies in the nearby universe where the black hole is typically less than 0. 1% of the total mass in stars of a galaxy. The dash lines then there are just to give you a bit of a guide on what that correlation might look like if black holes instead were 1% 10% or even 100% of their galaxy's mass in stars. And this is where those first black holes spotted with Jris T are sitting as over massive ones shown by the small squares and the green crosses which show the really bright ones. But then the results from Gears and Collaborators are shown by the bigger circles and bigger stars here. They show the stacked averages of various different subsets of those 600 galaxies that Gears and collaborators looked at different time ranges for example and they find that the average masses of the black holes are around about a million times the mass of the sun which are once again above those correlations that we would expect in the nearby universe not right down in the lower leftand corner like we'd expect them to be. Now admittedly, the average for the subset of galaxies that are slightly closer to us does tend to sit within the scatter area, but the ones further away earlier in the universe's history are even further from that correlation. So that tells us two things. First of all, that the apparently over massive super massive black holes that we've already seen with Jade Wis aren't actually weirdos. Even the faintest growing black holes seem to be turning up in this same part of this plot. And the second thing it tells us is that galaxies and black holes aren't evolving together like we necessarily thought they were. They don't seem to be evolving like up that correlation line like we thought. Instead, they're moving around this plot slightly differently than we expected. It's like they're moving horizontally across this diagram with time. essentially with the black hole forming first and then the galaxy of stars slowly growing in mass catching up with it over time. So is that then ### [9:03](https://www.youtube.com/watch?v=B9yDWbilIG4&t=543s) Paper 2: A direct collapse black hole with JWST? your answer? Well, maybe. But the problem is that we're still left with this idea of how do you even grow a super massive black hole that big in such a short space of time? Because we're seeing these growing black holes when the universe was very young. The only way that we know of to form a black hole that we have evidence for is when a star dies and goes supernova. That forms a black hole around about 10 times heavier than the sun. Pitily in comparison to a super massive black hole a million times or a billion times heavier than the sun. And there's only so fast that black holes can actually grow and swirl gas down into them to add to how heavy they are. In a similar way to, you know, in a bath or a sink, if you pull the plug out, all the water doesn't just disappear immediately, right? It takes time because there is a restriction on the flow rate, the amount of water that can actually get through that small hole. Black holes aren't holes. I do have a massive rant about that in my book. They're more like big mountains, but it's an analogy. I'll admit, not a perfect one. So to get around that problem, one idea that's been floated for a while is that if the conditions are right in the early universe, you might actually be able to skip all those steps of forming a star and going supernova and making a piddly black hole and instead take a big cloud of gas and just directly collapse it down into a black hole. And if you could do that, then the theory suggests that you might be able to make a black hole that's say a thousand or 10,000 times heavier than the sun to give you a head start on the black hole growth. We call these direct collapse black holes. And while there have been some tantalizing hints found with the Hubble Space Telescope that this could be possible, this month JDST also spotted its first candidate direct collapse black hole with this work from Van Doan collaborators. So, the authors were working on data from the Cosmos Web Survey that's been done with JWST to survey an area of sky where they spotted this strange looking galaxy that they dubbed the infinity galaxy because it had a very strange shape with two compact centers each surrounded by a ring giving it the shape of the infinity symbol or an eight on its side. So, they immediately suspected that what this was a direct like head-on collision of two spiral galaxies that was in progress. and they applied to get follow-up data with an X-ray telescope and a radio telescope that handily traced that light from the hot glowing material spiraling around a black hole. And they found that the brightest object in X-rays wasn't either of the center of those two colliding galaxies, but was actually from a section of the rings where those two galaxies were colliding. Not only that, but that X-ray emission was surrounded by a bigger cloud of glowing hydrogen gas, suggesting that what we could be seeing here is a direct collapsed black hole around a million times heavier than the sun that has just formed as a direct result of this collision. Now, let's not get ahead of ourselves cuz there could be other explanations for what's being seen here. First of all, there could be a third galaxy that we just can't see quite yet. perhaps if you've got something like a very faint dwarf galaxy. But then the problem with that idea is that as we saw before, roughly a galaxy's mass and a super massive black hole mass are correlated. So if you have a dwarf galaxy, you don't expect it to have a black hole mass this big. Or we could be seeing a runaway black hole here, right? So in the collision of the two galaxies, maybe one of the black holes in the center of one of those galaxies has been ejected outwards during that collision. And if that was the case, then it should have a different velocity to the rest of the things around it, a different speed. You should be able to see that it's moving. Now, Van Duck and collaborators didn't have that data. They needed to answer that question. So, they've applied for extra time with JT to observe this object again. And while those results haven't been published yet, Van Dam was actually quoted by NASA as saying that their preliminary results from that show that the black hole has the same velocity as the galaxies, confirming that black hole must have formed where it is. Plus, they also confirm that both of the two colliding galaxies also have growing super massive black holes. There's three in total in this system. So that puts page to the idea of it being an ejected black hole from the center of one of these systems because they both still have their super massive black holes. So this result is really exciting. And while it's not like direct confirmation that this like definitely happens, that black holes can form in this way, it's still the strongest piece of evidence that we have that if you have the right conditions of very dense gas like we expect to have in the early universe, then this mechanism could indeed be possible. So, thanks to ### [13:50](https://www.youtube.com/watch?v=B9yDWbilIG4&t=830s) Which came first: the galaxy or the supermassive black hole? the James Web Space Telescope, we're getting closer to answering that age-old chicken or the egg question of astrophysics, what came first, the galaxy or it super massive black hole? And thanks to these two research papers and all the other evidence we've collected over the past two decades, it's looking like the answer to that question is that the super massive black hole came first. ### [14:14](https://www.youtube.com/watch?v=B9yDWbilIG4&t=854s) Bloopers I don't think the rain is too loud. We'll just, you know, embrace this sort of ASMR space video. There's just been thunderstorms popping up everywhere today. Very frustrating. It's very heavy the rain now. Sounds great. I think I'm just going to have to persevere. I think it can't get any heavier. And then it's like, tada. How is there blue sky up there now? Like it was just absolutely pouring down a second ago. As a kid that grew up in Manchester, it was either raining all day or it wasn't raining. You know, there wasn't any of this like rain and then no rain. Not in Manchester, around Manchester. Language obviously. --- *Источник: https://ekstraktznaniy.ru/video/15145*