Mysterious objects near the beginning of time

0:01Oh, hey. Sorry, love to chat, but I'm busy shopping all the rollbacks and more at Walmart. Grab a what? Cancel that. I gotta grab these big savings on the Walmart app online and in-store like right now. See who? Nope, unavail. The only thing I want to see are the prices just lowered on Tech Home and all my must-haves. Wait, you want to shop Walmart with me? Alrighty, I think I can fit you in. We gather here tonight to bring women back to their rightful place. The Testaments, a new Hulu original series from the executive producers of The Handmaid's Tale. It's easier to accept a story than believe that the people around you are monsters.

0:44The battle isn't over. There comes a time when you have to take action, when you have to choose your own destiny. Never quite as it seems. Watch the new Hulu original series, The Testaments. Streaming on Hulu and Hulu on Disney Plus for bundle subscribers. Terms apply. It's Unexplainable. I'm Sally Helm. And today, I'm delighted to remind you about the existence of outer space. While I am doing things like compiling my documents for tax season or deciding whether it is time to replace the kitchen sponge, I sometimes like to pause and remember that astronomers are out there probing the many mysteries of the universe.

1:27I mean, astronomers do have to deal with their own kitchen sponges, but they also get to do things like look at the images sent back to Earth by this enormous, amazing telescope, the James Webb Space Telescope, JWST for short. It launched on Christmas Day 2021. We've covered it on the show before, but JWST is so powerful that it can essentially peer back in time. It allows scientists to see things that they have never seen. I use every second that I can squirrel away from my family, from teaching my classes at the university. I use every second of every day to just look at these images and dig deeper.

2:16We heard from astronomer Caitlin Casey about two years ago. I recently called Caitlin to check in, and she was right back where we left her, looking at the images that this ginormous telescope is sending back to us on Earth. Is the novelty, like, starting to wear off? Absolutely not. The novelty is there every single day. I'm still just as excited to look at JWST data as I was in July of 2022 when we all got to see images for the first time. It's given us so much of a new picture, new lens on how the universe came to be. I just can't get enough of it. The last time we talked to Caitlin, she told us about a mystery in the very early universe.

3:09These little smudges of light appeared all over JWST images. They were red and they were weird. One theory at the time was that they might be massive galaxies. But if they were, they were too big too soon. Here's what Caitlin told us back then. Some folks want to throw out our cosmological model completely. And that is, you know, that would change everything we think we understand about the universe. The other theory was that they might be supermassive black holes. But that also had people freaked out. The reason that is disturbing is because just like we don't know how to form stars really quickly, we have really no clue how to form black holes that are so massive.

4:02In the assembly of all of this research, I think we'll start to emerge with a new picture of the infant universe this first couple hundred million years in hopefully, you know, the next year or two. I'm not going to, don't quote me on that. Well, it's been two years now. Time to quote her. Sorry, Caitlin. But she did have some major updates. For one thing, those mysterious smudges of light have gained a new name, Little Red Dots. And it seems like they're called that because they look like Little Red Dots. Is that right? That's right. Shocker. Shocker. Yes, Little Red Dots are probably the most popular topic at scientific conferences discussing JWST data right now.

4:53I think we're converging a little bit. We're in a bit of a better place than we were two years ago, the last time I talked to y 'all. But it's, you know, a big mystery and so many details to unravel. Yeah, it does sound to me like you guys are starting to hone in, and it sounds like it's door number two. We're going in a black hole direction. For Little Red Dots, yes, it's door number two. We're talking about super massive black holes. I would say, I mean, you know, not everyone is sold on that yet. Now, that actually doesn't close the door entirely on door number one. There's still some really puzzling mysteries where we have really massive galaxies formed too early.

5:34But the overabundance of these little red dots in particular, that is pointing more and more towards the supermassive black hole hypothesis, that there are just oodles and oodles of black holes in the early universe. and we don't know what to do with them. Supermassive black holes are this giant mystery. We do not know why there seem to be so many of them hanging around in the early universe. But there is also a supermassive black hole at the center of our own galaxy. And we have no idea how it got there.

6:27If you looked at a picture of a little red dot, you would see a little red dot. But JWST is not like you and me. If you point it at a little red dot, it can show you the invisible light. Light that can't be perceived by the human eye. We disperse the light into effectively a prism. And that's like giving us a chemical fingerprint of what's inside that object. And there's a specific signature that black holes have that you can't really get any other way. You have to have a really massive object with material around it that's whipping around really, really fast. And it's whipping around really fast because it has such a strong pull of gravity.

7:15We have seen this over and over again in the spectra of little red dots. So overall, the consensus is this picture of supermassive black holes. But there is something very weird about these black holes. Let me first, you know, set the scene of what a typical supermassive black hole looks like. Astronomers are used to seeing supermassive black holes embedded in galaxies. in these big groups of stars. Every galaxy has a supermassive black hole at its center, which should sound shocking and also pretty profound. So the Milky Way is huge. It has a diameter of something like 100 ,000 light years. To put that into proportion relative to the black hole, I'm going to use an analogy.

8:11So if the Milky Way disk is about the size of the continental United States, the supermassive black hole at the center of the Milky Way would be about the size of the tip of a pencil. Wait, sorry. Galaxies are enormous. Black holes are tiny. The tip of a pencil inside of the continental United States. Not even the eraser. The tip of a pencil. Not even the eraser. Yeah. Now, the black hole, because it's actually so massive, it typically weighs about one one-thousandth of the total mass in a galaxy. That's a lot for just the tip of a pencil compared to the continental United States. But that relationship, one one-thousandth, it's pretty consistent across all galaxies.

9:07The assumption has basically been that the black hole and the galaxy grow together. That they kind of like always been linked. But Little Red Dots might be telling us a different story. Little Red Dots are so puzzling because they seem to be isolated black holes. We don't know why the galaxy that should be surrounding them seems to be missing. A missing galaxy. Where is it? One possibility is that the galaxy is there, but hiding. What we call a galaxy in the first billion years of cosmic time is very different than what we see in these gorgeous pictures from Hubble and even JWST of nearby galaxies.

10:03They have spiral arms and really sophisticated structure. Galaxies in the early universe are much, much smaller than galaxies are today. They lack organized structure. it's possible that the galaxy is there. It's maybe just a collection of a few thousands or tens of thousands of stars. Those stars might look very different than stars in the universe today. They might be exotic types of stars. But I think we're coming to the consensus that wherever they are, they're much fainter than the material that's being collected around the supermassive black hole that is shining brightly as the little red dot.

10:55It's also possible that the galaxy is not there and that we're learning something entirely new about how galaxies and supermassive black holes form. Maybe the discovery of Little Red Dots is telling us that the black hole forms first, I guess, and the galaxy lags behind. It's a bit as if a human were, you know, developing as an embryo, right? And only the heart grows first. And then the heart is born alone. And then the rest of the human grows around the heart. It would be like two things are wildly out of sync. Yeah, it's like a bunch of hearts floating around in space without their bodies. Without their bodies.

11:44And it just doesn't make a whole lot of sense given the consensus view of how these things grow through time that we've been, you know, building up for decades. And this is something that you can only really figure out by pressing up to the most distant objects found shortly after the Big Bang. You wouldn't figure this out any other way because you need to see, you know, what came first. Is it the chicken or the egg? And, you know, here we're maybe seeing that play out in real time. But if the supermassive black hole forms first, that leads to an obvious question. Do we know how supermassive black holes come to be?

12:31Thank you for pointing out the elephant in the room. Yeah, it turns out that while supermassive black holes are everywhere in the nearby universe, we just don't know how they formed in the first place. We now are thinking that little red dots are an essential piece of the puzzle. That's after the break.

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14:31The universe! It's big for me! The universe! Black holes. They are dark. They are massive. And there is one at the center of the galaxy that we are all in right now. My classic image of a black hole is of a dead star. this very bright thing that collapsed in on itself. So what you just described, astronomers call stellar mass black holes. These are objects that formed from the remnants of massive stars. They tend to have a certain mass range. They're like a couple of times the mass of our sun, or maybe even a couple hundreds of times. Supermassive black holes live in a different regime. They are about a million times the mass of the sun.

15:24And we've known about supermassive black holes in the early universe for a long time, like aside from these little red dots. We just have no idea how they got that big that soon. There is something like a speed limit to the growth of black holes. This is called Eddington Limited Accretion for the fans out there. Eddington fans, we got you. Yeah, yeah, Arthur Eddington, he was pretty smart. So what Eddington Limited Accretion says is that there is a fundamental limit at which a black hole can gobble up material. The more it gobbles up, that's called accretion, it shines more. As the black hole gobbles up material, that material creates something called the accretion disk, this like swirling hot ring of stuff around the black hole.

16:23That is what shines. and that shining actually exerts a pressure on the disk itself. So it's as if the gravity of the black hole pulls everything in, but the shining of the disk pushes everything out. And if you crank up the speed at which the black hole accretes material, it's going to shine too brightly that it'll actually cause the disk to effectively blow up. And it won't be there anymore. It is not clear how these supermassive black holes got so big so early without breaking that speed limit. There is a theory called super Eddington accretion, Basically a way that under certain conditions, black holes could grow faster.

17:22So then maybe these are just dead stars that grew really fast. But it's really hard to actually observe that happening. And then there's been another idea floating around that maybe these supermassive black holes didn't start out as stars. Maybe they just started out as big gas clouds. And somehow those collapsed. Direct collapse black holes are a phenomena where you take a primordial gas cloud. That sounds pretty fancy, but it's literally just a giant ball of hydrogen gas that comes fresh from the formation of the Big Bang. If you have this primordial gas cloud, some theories suggest that you can instantly collapse into something much more massive than any star that we see in the nearby universe.

18:18It's, you know, one of the many possibilities that as you have more primordial gas clouds, you can form more exotic objects that we just don't see in the universe today. J.W.S.T. has let us see an earlier freeze frame of the universe than we have ever seen before. And one extremely obvious part of it is these little red dots. So maybe they somehow fit into this story. That is one reason that scientists have been so obsessed with pinning down precisely what they are. little red dots are a puzzle a because they're red now a lot of things in space that are very far away look red to us because the way the light travels but little red dots actually are red these are intrinsically red like if a little red dot was right next to you it would look red Now, black holes themselves are not shining.

19:24It's the accretion disk that's giving off light. And the brightest supermassive black holes that we have seen in the past, they have been blue. We call these quasars. So if little red dots are supermassive black holes, it's just weird that they're red. The typical explanation for red things in the universe is that there's dust. Things are reddened by dust. It's similar to a hazy sunset. And so team after team has searched for dust in Little Red Dots, and we just aren't finding it. So Little Red Dots don't seem to be red because of dust. They seem to be red because they're fundamentally different black holes than the typical quasar we've known and loved for decades.

20:20And that gets us to the interesting idea of these being surrounded by not dust, but effectively an atmosphere of a star. This primordial star gas could be what is making the little red dots red. And this combination, a supermassive black hole wrapped in the atmosphere of a star, we have never seen this before. We didn't know that it happened, let alone that it happened so often in the early universe. It's kind of a new object in space. Some people have now started to call the Little Red Dots black hole stars.

21:13So Little Red Dots, we knew nothing about them before JWST. They're only in the early universe. So we're just pushing now JWST to do a better job to find Little Red Dots even earlier in the first 400 million years of cosmic time because there are a lot of different ways that Little Red Dots can teach us about supermassive black holes, how black holes grow at the beginning of time, and how supermassive black holes relate to the galaxies that they live in and we see in the universe today. Maybe all supermassive black holes were once Little Red Dots, or maybe not. There's a lot that we still don't know.

21:59One detail I'll add is that we have guesses as to how massive the supermassive black holes and little red dots are. But those guesses are calibrated off of black holes we know and understand in the nearby universe. And maybe some of the fundamental relations that we take for granted in the nearby universe just don't hold at early times. So we actually might not know the masses as well as we think we know them. And it turns out, you know, guessing the mass is pretty important to understanding how the thing formed. We do the best job we can just looking up at the night sky. But we don't have real experiments that we can conduct on the universe itself.

22:49You know, what I love about this field is it always has a surprise for you. You know, we turned on JWST a couple years ago, and it felt like we went from a black and white world to a colored world. And with every leap, you learn something completely surprising about the universe. And here, I think it happens to be this story of the first billion years of cosmic time. It's complex. It's messy. There are a lot of black holes. We have no idea how they form. And we don't know where the galaxy is around them. And it should be there. I don't have answers today for you. But, you know, we're working on it every single day.

23:47Maybe in another two years we'll have answers. If you do come back on Unexplainable for appearance number 015 in 10 years down the line, what would you hope to be able to tell me? That's a great question. And, you know, the true answer is that I would never be able to predict it. The most exciting thing are the things that I can't even imagine.

24:16This episode was produced by me, Sally Helm. It was edited by Meredith Hodnott and Joanna Solitaroff. Christian Ayala did the sound design and the mixing on this episode. Melissa Hirsch checked the facts. Jorge Just and Julia Longoria are our editorial directors. Amy Padula and Noam Hassenfeld are some of the things that the James Webb Space Telescope has not yet been able to see. And Burt Pinkerton waited for a response, but no one could help. So she went to the Doctopus. Where's Eric Flapton? The Doctopus shook her head. In a white room with black curtains. In the station where the sun never shines.

24:58Where the shadows run from themselves.

25:04Thanks, as always, to Brian Resnick for co-creating the show along with Burt and Noam. And special thanks today to Anna Degraff for helping me understand Little Red Dots. If you have thoughts about this episode or about the show or about outer space, please write to us. We are at unexplainable at vox.com. Getting these emails is really a highlight of our day. So if you are on the fence about writing in, I say go for it. If you want to support the show and help us keep making it, please join our membership program. It is at vox.com slash members. You get ad-free podcasts and unlimited access to Vox journalism.

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26:08Thank you.