A Coup De Grace in Space

Big Picture Science Introduction

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0:43Sometimes you need to step back and get the big picture. The whole expanding 93 billion light years across big picture. And when you look up, that's when the deep questions descend upon us. Where did I come from? Where's it going? How did it all begin? Astronomer Neil deGrasse Tyson reminds us that the universe isn't out there. It is everywhere. We are a part of the universe. And there's a lot of weird stuff going on in it. So black holes that are growing rapidly and are consuming gas from their surroundings.

1:16Welcome to Big Picture Science. I'm astronomer Seth Shoste. I'm Molly Bentley. In this episode, a new space observatory is poised to provide an expanded field of view of some of the strangest phenomena in the cosmos. The long-awaited successful launch of the Nancy Grace Roman Space Telescope will help us understand black holes, dark matter, and help us find exoplanets. It's a flagship mission underway now, making this episode a coup de grace in space.

The Legacy of Nancy Grace Roman

1:44In some ways, the first coup de grace in space was the launch of the Hubble Space Telescope, because it was astronomer Nancy Grace Roman, who in 1959 created NASA's Space Astronomy Program, that laid the foundation for the Hubble Space Telescope. A year before her passing in 2018, at the age of 93, Dr. Roman did a series of interviews for NASA.

2:17My name is Nancy Grace Roman, and my role in Hubble was as program scientist. And that means that I basically tried to sell the program, trying to convince people that it was very well worth doing. When Hubble launched in 1990, it was not the first space telescope, but it was the largest and most versatile up to that point. Because of the role she played in getting the pioneering telescope off the ground, Dr. Roman became the mother of Hubble.

2:49Lofting a telescope above the atmosphere offers astronomers an important benefit. I like to describe looking through the atmosphere as being something like looking through an old stained glass window. The window has dust on it, so the background is kind of scattered and bright. Atmosphere scatters light, too. That's why we don't see stars in the daytime. Falcon Heavy is in startup. The launch director is go for launch. So let's sit back and watch as Falcon Heavy takes the Nancy Grace Roman Space Telescope to space.

3:20While Dr. Roman was around for the planning of the mission, she would never learn that the new telescope since Skyward in 2026 to orbit above the turbulent atmosphere would carry her name. Three, two, one, ignition, and liftoff. Go Falcon Heavy and go Roman Space Telescope.

Surveying the Unknown with Roman

3:42I am Julie McHenry. I'm an astrophysicist at Goddard Space Flight Center, and I serve as the senior project scientist for the Roman Space Telescope. Julie, you are the project scientist for the Roman Telescope. Now, from what I understand, the job of the senior project scientist is to guide the scientific vision for the telescope. What is your vision? I want a telescope that does extraordinary ambitious surveys that provide a massive science return for everyone.

4:15What is a survey mission? People might think of surveys as something that you do in your neighborhood. When it applies to a space telescope, what does it mean? Well, actually, I mean, I think your survey of the neighborhood is not an analogy I've heard before, but I think you could make it work for Roman. But imagine that your survey isn't of your neighborhood, isn't of somewhere you know, but it is a survey of the unknown, and that you have things that you know you're going to measure because you've sort of already seen what was there at the 30,000-foot level,

4:49but now we're going to delve into the details over a large area. So we're going to find all the things that are there with exquisite sensitivity and performance. Roman is built to answer some of the most fundamental questions there are about the universe. And one of those fundamental questions that we've been asking for a long time and still don't really know the answer to is, what is the universe made of?

Dark Matter and Dark Energy

5:16Hi, I'm Jason Rhodes. I'm the chief scientist for astrophysics, heliophysics, and fundamental physics at NASA's Jet Propulsion Laboratory in Pasadena, California. And so about 95% of the universe is made of this dark stuff, a combination of dark matter, which only interacts gravitationally, doesn't interact with itself, it doesn't interact with light, so we can't actually see it directly. And dark energy, which is the name we give to whatever the phenomenon is that's causing the universe to expand faster and faster, this accelerating expansion.

5:50So this is 95% of the universe that's dark, and that dark universe really determines the history of the universe because there is the dark matter, which tends to pull things together due to gravity, and the dark energy, which is becoming more powerful over time as the dark energy causes the universe to accelerate, and this is tending to push things apart in the universe. So there's a push and a pull in the universe that goes back to the very beginning of the universe, and Roman is going to make observations of galaxies to try to understand both that dark matter and that dark energy.

6:25It's rather remarkable that so much of the universe is kind of MIA, that we can't see it. We can measure its presence, but you can't make a photo of it. That's right. So one of the techniques that we use to measure, for instance, the dark matter, is we look at the shapes of distant galaxies, and these are galaxies all the way back to the early times in the universe. And we look for small distortions in the measured shapes of those galaxies, and those distortions are caused by the fact that light from those galaxies comes to us not on a straight, unobstructed path,

7:03but it passes by dark matter structures on the way. And one of the consequences of Einstein's general theory of relativity, our theory of gravity, is that mass bends space. So the space between us and these distant galaxies is bent, and that changes our measured shapes of these galaxies. Now, we can't tell anything really about the dark matter by looking at one single galaxy, but what Roman is going to do is it's going to map out the shapes of hundreds of millions or even perhaps a billion galaxies

7:35and look for very small, coherent shape changes in those galaxies or shape correlations, and that's going to allow us to make a map of where the dark matter is in the universe at unprecedented level of fidelity. To my mind, the most important discovery from Hubble is the discovery of dark energy. Again, Nancy Grace Roman in 2017. There have been a lot of interesting discoveries, certainly, but I do feel the dark energy is the outstanding discovery.

8:06And what that means is simply that we always thought that space would contract because gravity would pull it together. We knew it was expanding, but we thought the expansion would slow down. Well, instead, the expansion's speeding up, and that is a very exciting thing to me. At the end of the 90s, observations have showed us that the universe is accelerating, so it's not expanding constantly, it's not slowing down, but is in fact accelerating.

8:39Roman is going to be able to continue those measurements out to higher redshifts, so it will give us more insight into the behavior of the expansion history of the universe at earlier times. And that is important for understanding the fundamental nature of dark energy. And the reason that is currently important is in the last year, there's been suggestions that maybe one explanation of dark energy, of the acceleration, is that you've got some fundamental property of space-time that pushes things apart.

9:12And the easiest way to describe a universe with this is to say that that property of space-time is always the same. And there's hints that that might not be the case. And one way to measure that better is to look further into the universe at earlier times. So the word there that's key is history. You want to know what kicked it off, perhaps. Like, what was happening in the early stages of the universe that might have kicked off this acceleration? Yeah, no. Okay. So you might want to know that too, but I think we're more interested in understanding more fundamentally

9:46what properties of the universe makes it behave the way that we see it now. So, yes, I mean, the very earliest times are important, but, you know, I care about where is our universe going? Are we going to continue to accelerate and expand faster and faster and faster until eventually everything gets ripped apart? Or is it, is the acceleration going to turn around and start slowing again? And I'm driven by wanting to understand what it is that's making it behave like that in the first place.

10:18I mean, there's something really fundamental that we don't understand about how the universe we're in works. I mean, it feels like we're almost on the precipice of a big leap in fundamental understanding of how our universe works. And that's very exciting.

Comparing Roman and Hubble

10:34Many of our listeners will be familiar with the Hubble Space Telescope. Give me a quick comparison of this new instrument with Hubble. Yeah. So it's fairly easy to compare Roman with Hubble because they're both about the same size telescope, both about a 2.4 meter mirror across. So they both have roughly the same light gathering power and they both cover roughly the same wavelength ranges with Roman having a little bit more limited wavelength range.

11:05It covers, Roman covers the visible as well as the near infrared wavelengths that Hubble covers. But the true power of Roman is its camera. Advances in detectors over the last few decades have allowed us to build a camera for Roman that has almost 300 million pixels. So this camera covers an area on the sky that's about 100 times as large as the similar cameras from Hubble. So every time you take a picture with Roman, it's roughly similar to a picture you'd see with Hubble, but just 100 times the area of the sky.

11:41Roman's superpower is that we have a very large field of view. So our field of view is more than 100 times larger than the equivalent on Hubble. But when you take into account the efficiency of our observations, we can survey the sky a thousand times faster than Hubble. And that means, for example, a survey that would take one month with Roman would take a century with Hubble. Well, one of the things we want to do is we want to push further and further back into the early universe.

12:14And to do that, we want to look at redder and redder light. And the reason for that is as the universe expands, there's a Doppler effect so that galaxies that are further away from us are moving away from us. And this shifts their light into the red. And so by using a telescope like Roman to study the infrared, we're able to look further and further back in time and look over a longer time baseline about how dark matter and dark energy have shaped the evolution of the universe.

12:44We've been discussing the fact that these telescopes operate in the infrared, the Roman telescope in particular. And, you know, just to get some idea of how your view of things changes when you look at infrared wavelengths. Suppose I, you know, did that here in my backyard. I used an infrared something that would allow my eyes to see infrared. What would be different? What would it look like? Well, infrared is essentially heat vision.

13:14And so when you see in a movie or something like that, night vision goggles, what they're using is infrared sensors and infrared sensors that are sensitive to similar wavelengths to what Roman is. So you would really see heat rather than, you know, the optical colors you see of someone. But what would be interesting, of course, is if it's pitch black at night and there is a person, they're still going to show up on an infrared camera. So in the same way, we're seeing sort of different things and different aspects of astronomical phenomena with infrared.

13:51And one of the things that makes Roman so exciting is there's a number of ground-based telescopes, including the Rubin Observatory in Chile, that are operating right now. And they're taking images in optical colors, visible colors like what we see with our light, because those are the easiest ones to take on the ground. And so when you combine the Roman data from space and the infrared with the visible data from Rubin on the ground, you get a huge increase in the amount of science, the precision of science, and really the science that you can do with these multiple telescopes looking at the same area of the sky together at different wavelengths.

14:28Roman is also going to make huge inroads into another very fundamental question.

Hunting for Exoplanets

14:41And that question is, are we alone in the universe? And there's a few ways that Roman is going to start to tackle this in ways we haven't been able to before. We know of about 6,000 exoplanets. These are planets outside of our solar system. And those have been discovered over the last 30 years. But Roman is going to discover about 100,000 more exoplanets. So there's going to be a huge explosion in the number of exoplanets. And what's really exciting is Roman will use a technique that's not been used very much before to study exoplanets.

15:14And that will allow us to study exoplanets that are smaller and further away from their stars than previous techniques allowed. Would Roman be able to detect the Earth from, say, 100 light-years away? I mean, you know, would it know that this planet is probably amenable to life? Roman won't be able to do that. However, Roman has an instrument on it called the coronagraph. And this is an instrument built here at JPL, where I'm talking to you from. And a coronagraph is an instrument that blocks the light from a star so that you can see the planet.

15:48And the Roman coronagraph will be about 100 to 1,000 times more powerful at blocking starlight than any previous coronagraph flown in space. And it's going to do this by using a number of new technologies together in space for the first time, including small deformable mirrors with thousands of pistons. And you change the shape of these mirrors to correct for any imperfections in the telescope or the optics so you're not scattering starlight into the detector where you're trying to detect the planet.

16:20And so what Roman will be able to do is for the first time, we'll be able to see a reflected light planet about the size of Jupiter with Roman. But the key here is we're testing these new technologies. And NASA then plans to use these new technologies on a future coronagraph, on a future telescope that we're now calling the Habitable Worlds Observatory. And this more powerful telescope using these Roman-proved technologies would have the ability to detect signs of life on an Earth-like planet around a sun-like star if that star was fairly close to us in the universe.

16:57So while Roman won't be able to find signs of life, it's within our technological grasp and within, hopefully, my lifetime that we will have that ability to detect signs of life around other planets using these technologies we're proving out on Roman. So for me, this is another really, really exciting aspect of Roman and one that, you know, I think people who aren't astronomers can get behind, you know, trying to understand is there life elsewhere in the universe?

17:28Did you ever meet Nancy Grace Roman? I never had the pleasure of meeting her, but a number of my colleagues met her and, you know, she was universally loved and admired and an incredible advocate for space telescopes. So it's really, I think, fitting that the woman who was perhaps most responsible for making sure that the Hubble Space Telescope happened has a telescope that's 100 or 1,000 times better named after her. Okay, finally, Julie, the moment that the Nancy Grace Roman Telescope is operational, it's up and running and it's collecting data.

18:06You are the senior project scientist. What is the first thing that you do when they say, okay, it's collecting data?

18:15You know, people have asked me what I'm most excited about looking for first. And, I mean, it's almost like asking me to choose from my favorite children. I mean, I'm not, I can't really do that. I'm just excited to see what Roman is going to show us about the universe for the first time. And I almost don't matter where we point. I just want to see a big Roman image for the first time. I think that's going to be just mind-blowing. Julie McHenry is an astrophysicist at NASA's Goddard Space Flight Center, where she serves as the senior project scientist for the Roman Space Telescope.

18:59Jason Rhodes is an astrophysicist and observational cosmologist and the NASA Jet Propulsion Laboratory project scientist for the same instrument. Coming up, I chat about the past and future of astronomy with this guy. It's too easy to think that all the good stuff has already been done, all right? Of course, they thought that 120 years ago. There's nothing more to be discovered in physics. So I am not going to be that guy that says, I'm content in what we know.

19:30There's nothing left to discover. Astrophysicist Neil deGrasse Tyson joins us next. This episode of Big Picture Science is a coup de grace in space.

19:43This astronomer needs no introduction, but...

Talking Astronomy with Neil deGrasse Tyson

19:59Hi, I'm Neil deGrasse Tyson, your personal astrophysicist, and I'm director of New York City's Hayden Planetarium at the American Museum of Natural History. It's always good to chat with Neil. He and I concur that it's no surprise that astronomy and cosmology discoveries are top of your news feed. The public remains enthusiastic about all things space. And that's why, Seth, you know, it's headlines. Is it a new black hole? If we launch a new space telescope, the Nancy Grace Roman Telescope launched successfully,

20:31and that made news. Is there science on it yet? No, we're not going to have science for another six months. But the fact that we're about to do some new great science with dark matter and dark energy and exoplanets, that's news. As well as being an enthusiastic speaker, Dr. Tyson is a prolific writer. His two books, released in 2026, extend a long list of publications, the most recent being Lost in Space, 5,000 Facts for Navigating the Universe. Seth and Neil discussed, astronomer to astronomer, some of those facts,

21:04and put the Roman Space Telescope in the context of a long evolution of advancements and ever more sophisticated technology. They also talk about how astronomy has changed over their careers. But one thing that hasn't budged, says Dr. Tyson, is astronomy's ability to attract and dazzle the public. People love learning about planets, not just in the abstract, but can they support life? Right now, we're rising through 6,000 exoplanets in the galaxy.

21:3630 years ago, that number was one. Okay? So, that's always a hot topic. The frontier mysteries are always hot. Black holes, dark matter, dark energy. You know, you could just track what topics are covered in sci-fi movies and say, okay, let's bring that into the dome, but with real science behind it. But also, think about it. Let's say you're a geophysicist and you want to attract eighth graders into your field. You can say, oh, geophysics, we study continental drift and volcanoes.

22:09Who loves volcanoes? They say, wow, that's cool. Okay? And then any one of us, we, the astrophysicists, follows them in the classroom and say, do you like volcanoes? Okay, yeah. On Jupiter's moon, Io, it is the most volcanically active object in the solar system. On Mars, there's Olympus Mons, which is the largest volcano in the solar system. It's inactive, but it is the largest. So, because astronomy, I think, dabbles in or thrives in extremes, extreme temperature,

22:45pressure, time, space, density, we kind of win every contest when it comes down to attracting people to the frontier. One thing that's changed in astronomy is the fact that astronomy is no longer heavily a science that's conducted at a distance, right? I mean, 200 years ago, you can only observe through a telescope if you had one, you know, the moon or Mars or whatever you were interested in. Today, we can go to some of these worlds and have. So, if somebody were to ask you, what's the big change here in the 20th, 21st century in

23:22astronomy, what would you point to? Would you point to some instruments or would you say the ideas are different? Yeah, I think more about that question than you're probably bargaining for here. So, let me edit it down to a simple answer. I think the two greatest advances in the 20th century are two things hardly anyone will say. Most will say, oh, atomic weapons or this, right? No, two things. First, electricity.

23:52Second, the computer. Okay? Transform civilization. All right. Now, in astronomy, I would say, in the 20th century, we opened up windows to the universe that were not previously known even to Galileo. We opened up radio waves and x-rays and gamma rays and ultraviolet and infrared. These bands of the electromagnetic spectrum, once we figured out that they're there and the universe is talking to us in those bands and we designed detectors, we needed the help

24:24of physicists to do this because astronomers are not necessarily the tech heads here. So now, all bands of the spectrum are available to us as well as non-electromagnetic bands. We have neutrino telescopes and gravitational wave telescopes. So, those are the biggest advances, I would say, in the 20th century and beyond. So now, we sit back and let all the languages of the universe arrive at our detectors. So, that's kind of a technological evolution in a way because, you know, you couldn't have

24:55done that. You might have known about infrared 150 years ago, but you didn't have any telescopes that would allow you to see what in the universe is emitting infrared as it was, as it were. But here's another question actually about technology because when I was a kid, you know, my parents would put me on the train to New York and I would go visit my cousins in Brooklyn, but I would always take the subway to Manhattan to visit the Hayden Planetarium, invariably. And one thing that impressed me every time, particularly as a kid, was the huge Zeiss projector in the center of the room there, you know, projecting images of the sky onto the dome.

The Digital Evolution of Planetariums

25:30Has the planetarium changed? I mean, we have all sorts of technology today that we didn't have when the Hayden Planetarium was being built. Has that affected the subject of your planetarium shows in any great way? Yes, entirely. That's a great question, a perceptive question. And I grew up in New York City, so it wasn't just on a special trip to the Hayden Planetarium. It was a major part of my childhood. And yes, the huge Zeiss projector in the middle, which looked like a giant bug, all right?

26:02And that was responsible for putting the stars on the night sky. When we rebuilt the place, now a quarter century ago, we updated the Zeiss projector from the Zeiss Model 6 to the Zeiss Model 10, I think it is. And it's way more capable. In fact, it can put things on the dome that are dimmer than your naked eye limit can detect. And you can bring binoculars into the dome and resolve the detail. That's how good it is.

26:33So it has deep sky objects that resolve into globular clusters and spiral galaxies with binoculars. Around the same time, all data are becoming digital. Hubble, in the 1990s into the 2000s, this is what made Hubble so significant on the landscape of people's awareness and appreciation of astronomy, because everyone was getting a computer in the late 1980s, early 1990s. Hubble comes around and is producing digital pictures made available through NASA.

27:03Every third person's screensaver or desktop pattern was a Hubble image. Which, what am I getting at, that now that we're in the digital era, we have digital data on where, not only where everything is in the sky, but how far away it is. Load that into a computer, have a fisheye lens where you reverse project through it, sending an image onto a dome. And now, it's not, oh, will I be able to see the constellations of the night sky when I go

27:36to the planetarium? Yes, my son, my daughter, but you'll also be able to visit them. Will I see other galaxies? Yes, but you will go to the other side of those galaxies. You will go to the beginning of the universe itself. So, once you add the time dimension to this, it's no longer just, tell me about the constellations and the constellation lore. Once you can visit the stars and the constellations, you can say, oh, where was the first exoplanet? It's that star over there. Let's go there.

28:06You are not using the Zeiss projector for any of that. We pull out the Zeiss only when we're doing a pure night sky talk. But when we go to the moving frontier of astrophysics, we've got the digital projectors. And we maintain, I have an entire person whose business card is manager of the digital universe. When you hand someone that card, that's badass. So, it requires the care and feeding of the data sets that go into this, where we're plugged into all the latest survey data that's coming down the pipe from space-borne telescopes as

28:41well as Earth-bound telescopes. Yeah. That's certainly new. I mean, again, going back a century or two, right? All the data was on photographic plates, glass plates that were in somebody's cabinet in their office somewhere. And you didn't know where it was. And probably they didn't know where it was either after some point. But, you know, you couldn't get to it. That accessibility obviously leads to maybe citizen science projects or whatever. I mean, it really is a difference when anybody can get to the data.

29:14But sometimes I feel as if all the profound discoveries have already been made. And if someone's sitting next to you on the bus and they say, so, you know, what have we learned in the past, I don't know, 10, 20 years that's profoundly important? You know, what would you say to that? Yeah, it's too easy to think that all the good stuff has already been done. All right. Of course, they thought that 120 years ago. There's nothing more to be discovered in physics.

29:44We've got, you know, electricity, thermodynamics, gravitation. We've got optics. And we're done here. There's just some clouds on the horizon. We're just worrying about the next decimal place in our measurements. And within five years, within five years, the quantum would be discovered. Another couple of years later, special theory of relativity would be discovered. E equals MC squared. In another 10 years, the expanding universe. And that our galaxy is not even alone in the expanding universe.

30:17Oh, my gosh. So I am not going to be that guy that says, I'm content in what we know. There's nothing left to discover. Because add up dark matter and dark energy as forces on this universe. And it's 96% of what's driving the universe. And all of our biology, chemistry, and physics that we know and love, that we learned out of textbooks in all of our classrooms, all of that is less than 5% of what's actually happening in the universe. So, I don't know what the next discovery will be, but I would like to think that it'll give us some headway into this 95% that we don't know about.

30:59And what a privilege it is to know so much about the universe that we can quantify our ignorance. That's a special place to be when you think about it. Yeah, and I must say it's somehow uplifting to know that this subject is so deep in the sense that you never get to the bottom, right? That there's always something new to discover. At least that's been the case so far in the first 300,000 years of almost aliens, right? Well, so there's this document from 1945 or 46 written by the then equivalent of today's science advisor to the president.

31:36His name is Vannevar Bush. His name is Vannevar Bush, a science advisor to Truman, and I think later to Eisenhower, but he published this document called Science, the Endless Frontier, informed by what role science played in our health, our wealth, and our security going into and coming out of the Second World War. But to even think of it as an endless frontier, that took some foresight. And he wasn't even a scientist. He was like a policy wonk and with a science background.

32:09So my poetic version of that reality is that as the area of our knowledge grows, so too does the perimeter of our ignorance. And that's just a statement of how it's always been. It's not wishful thinking for the future. Yeah, it'd be nice to have job security, but maybe the day will come where our area of our knowledge grows and the perimeter shrinks. Ooh, that'd be an interesting time.

32:41And then one day we wake up and say, we know everything there is to know about the universe. And you know how we know when we've reached that point? Because everything will be completely explained without appealing to the supernatural or to magic or to voodoo, right? Everything would have an understanding and a cause and effect. And in a sense, we would be in control of all phenomenon in the universe. Then you're done. Give me another universe at that point.

33:11Well, finally, Neil, let me ask you about the perennially popular topic amongst the public. And that is black holes. You are fascinated by black holes. But is there anything to be said about black holes that hasn't been said?

The Mystery of Black Holes

33:25Yeah, I think so. Oh, by the way, I disagree with you. It's not black holes. It's aliens that people ask most about. It's a close second to aliens. Well, aliens are my day job. So, you know. Oh, gotcha, gotcha. They don't always ask about that.

33:41So, yeah. So black holes, kids are intrigued by them. I think for the same reasons they're intrigued by T-Rex, because both of them can eat you. What we don't know is what's going on inside a black hole. The equations suggest that a whole new space-time opens up in front of you on the other side of the black hole as the future history of the universe you just left unfolds before your very eyes. This is really exotic thinking.

34:14The equations allow it, but – and how are you going to test it? Seth, you want to be the first one to go in a black hole? You ain't coming out. So how are you going to even report your results? Yeah, it'd be a bit of a stretch. It'd be – I see what you did there. You can be spaghettified falling into a black hole. In fact, I composed a poem about that. May I recite it if I remember it? Of course. Okay. On a feet-first dive to this cosmic abyss, you will not survive because you will not miss. The tidal forces of gravity will create quite a calamity when you're stretched head to toe.

34:50Are you sure you want to go? That's a separate book that I wrote. I had a column called Merlin. It's Merlin's tour of the universe. It's in that book. But anyhow, so I think what's inside a black hole is still a mystery. We're still trying to hash that out. General relativity, which gives us black holes in the first place, fails in the center of the black hole at that singularity. It's been playfully described as the place where God divides by zero. If you remember your math class, you're not supposed to divide by zero.

35:23The equation blows up, such as what happens to Einstein's equations at the center of a black hole. But otherwise, we're doing gangbusters. We're measuring colliding black holes and the ripple in the fabric of space-time that it sends out, measured by the Laser Interferometer Gravitational Wave Observatory, LIGO, sensibly abbreviated. Nobel Prize has been given for those measurements. And I don't know the latest. There's thousands of mergers. Black holes colliding with black holes.

35:53Black holes colliding with neutron stars. Neutron stars colliding with neutron stars. All these places are extraordinary and extreme sort of endpoints of what matter does under the influence of gravity. So, yeah, I think they'll always be a fascinating topic. And I'm told Disney is remaking their original movie, when was it, from the mid-'70s, late-'70s, The Black Hole, which by my measure is one of the ten worst movies ever made. So I really hope they get an actual advisor on this at the time.

36:25I remember coming out of high school, I saw the movie, I said, I could have advised a bit, call me Disney next time. Okay. They clearly had no advisors whatsoever. And so I hope they do better this time around. Yeah, I'm with you on that. I saw it as well. And I came out thinking, oh, well, the best thing about that movie was the popcorn.

36:46Well, Neil, I want to thank you very much for speaking to us today, because it's been, as expected, extraordinarily interesting, also informative. And, you know, makes me think about things that, you know, I don't think about all the time, even though I'm in the field of astronomy. So there you go. Thanks again very much for being with us, and we hope to talk to you again. And thanks, Seth. It's been too long. We should hang out again. We used to hang out every couple of years. We'd find some excuse. Let's try to do that again. I'm all for it.

37:17Neil deGrasse Tyson is an astrophysicist and the director of New York City's Hayden Planetarium at the American Museum of Natural History. And he is the author of Lost in Space, 5,000 Facts for Navigating the Universe. Coming up, we are drawn further into black holes when a new bizarre discovery suggests that not just galaxies, but even some stars have these monster objects at their cores.

37:55It doesn't look like a normal star, right? Like the sun, we just had the solar eclipse, and we could all see the sun looks like a perfect, you know, circle. This would be like a big blob of gas that becomes much more unstable and much more dynamic. This episode of Big Picture Science is a coup de grace in space.

38:27We've heard about a couple of revolutionary instruments used to peer into the cosmos. The pioneering Hubble Space Telescope that launched from Kennedy Space Center in 1990, and the Nancy Grace Roman Space Telescope that was rolled to the Florida launch pad in August 2026. This next space telescope was sent skyward from South America. It, too, has fans.

38:58It is, hands down, my favorite telescope. Quite a statement considering others in the running. NASA's flagship James Webb Space Telescope blasted off from the Guyana Space Center in 2021, aboard a rocket provided by ESA, the European Space Agency. It gives us images' orders of magnitude better than those of Hubble. So, the thing that it does is that it's extremely sensitive, and so we can see extremely faint sources, and we can see extremely red sources.

39:29So, we can see wavelengths we've never explored before, and that just opens up a huge realm of possibilities.

Discovering Little Red Dots with Webb

39:35Hi, I'm Anna de Graaf, and I'm an astronomer at the Max Planck Institute for Astronomy. You know, Molly, what Dr. de Graaf says about red sources can mean one of two things. Either the source is actually red, I mean, that's its color, or it's very far away. Now, in this case, the Webb Telescope can look back billions of years, and in fact, to within only a few million years of the beginning of the universe. And because the universe is expanding, things that are very far away are, well, they're expanding away from us. They're moving away from us. And because of the Doppler shift, that means they're also very red.

40:09To observe it, of course, you need a telescope that can observe at very red wavelengths, infrared wavelengths. Now, one of the most exciting things for astronomers is to discover new objects. You know, objects that they never knew existed. And some of these objects can be quite violent. That certainly is the case with black holes. They can violently suck in nearby gas, even stars. But what Dr. de Graaf and her team found using the James Webb Telescope was something even more bizarre than these gas cobblers.

40:41They believe they discovered a kind of black hole-star hybrid, a black hole-star. So the name actually came from our previous work where we showed for two objects individually that unambiguously we could not fit it with any other galaxy model or any other black hole model. And we showed that it has to have these sort of quasi-stellar properties, except that it is so much more luminous than a normal star is. And so we kind of hypothesized that the only objects in the universe that we know can produce so much luminosity are accreting black holes.

41:20So black holes that are growing rapidly and are consuming gas from their surroundings. As the gas falls into the black hole, a lot of energy is released. And so that is the light that we actually see. Anna de Graaf told Roland Pease that the discovery may change our understanding of how we get supermassive black holes. Now, we know that these monsters are in the center of galaxies, but we've not understood how they were formed. So her discovery and that of her team might answer that question. And it all began with something seemingly ordinary, when the Webb telescope picked up unusually intense pinpoints of red light.

41:56But they didn't shine the way ordinary red-shifted stars do. Unlike them, these pinpoints of red had no blue light. First of all, the colors are very peculiar because they are extremely red. And the other thing is a morphology. So they're really point-like, almost like a star. And those have now turned into one of the biggest debates, I think, in the scientific literature at the moment. I mean, it sort of sounds like, well, what else can you learn from a dot? But one of the things you can tell from the James Webb Space Telescope is you can look at the colors, like you say, of these.

42:30You can break the colors down into a lot of detail. And that's where you're getting a lot of your clues? Yes, that's right. And one of the biggest advances of JWST actually over Hubble is that it can do what we call spectroscopy. And so what that means is that you split the light into kind of like a rainbow, except that we don't see the blue part of the rainbow, but only the reddest colors of the rainbow. And so what it gives you is a very detailed color information on the source you're looking at. And every source in the universe has its own unique spectrum, we call it.

43:03It's sort of like a color fingerprint of an object. And based on that, we get a lot of information on what sort of elements are in there, what the velocities are of, say, the gas in these sources. So it gives us a huge, important constraint on what physically the objects actually are that we're looking at. So talk me through a bit of what that tells us with these little red dots in terms of you can work out their temperature, can you? For example, you can work out their composition. Yeah. So the spectra of the little red dots are truly unlike anything we've seen before.

43:37And so what we do learn is we see a few very important features. So on the one hand, we see almost no UV light, so no blue light. No high energy light, in a sense. Yeah, so not as much high energy. And then at a very specific wavelength, all of a sudden, we see a lot of emission. And then it extends all the way into the red. This very specific wavelength is something we call the Balmer limit. And this is a transition in the hydrogen atom. So it's a feature that hydrogen produces under certain conditions, certain temperatures and certain densities.

44:11Talk me through that. Yeah, so hydrogen gas, when it's very warm, so sort of 5,000 to 10,000 Kelvin, so kind of a bit hotter than the sun. I was going to say that's more than warm. It is, yeah. For astronomers, it's warm. For the normal person, it's pretty hot. So it's kind of like the sun. And density is also actually kind of similar to the sun, like the outer parts of the sun. And so it's something we see in the spectrum. And so what this means is that we see direct evidence for very dense, almost stellar-like emission in these little red dots.

44:45And it's coming from hydrogen. So this is hot hydrogen that's radiating the light that you're seeing in your telescope. Yes, that's what we're... So we see unambiguous evidence for that. And the other clue that we see is that we see a lot of red light. But the red light also kind of tapers off towards very red wavelengths. And this is a very important clue. Because, again, actually, if we take the sun or other stars as an analogy, this is what stars do as well. They radiate the most at a specific wavelength. And then there's some emission coming from other wavelengths. But it tapers off on both sides.

45:16And so this is what we call black body emission. And so the little red dots all show emission like that as well. So it's like having something that looks like a star, but it's 10 billion times more luminous. Oh, right. 10 billion. Sorry, you've raced past that. 10 billion times more luminous. So it's sort of like a star, but it's way too bright, you're saying? Exactly. So it's a really bizarre type of object. So it's not exactly like a star, obviously, right? Because a normal star cannot become that luminous. And this is one of the reasons why these sources have sparked so much excitement.

45:47Because it's something that we, you know, it's totally new to us.

Black Hole Star Hybrids

45:50I mean, the reason I wanted to talk to you was because of this idea of black hole stars, which is, I think, one of the favoured explanations for these little red dots. So these would be, well, how do you combine black holes and stars? Yeah, that's a very good question. The idea is that we might have a growing black hole, but then embedded in this very, very dense gas, that's lit up essentially by this accreting black hole, and then start to shine a bit like a star. Give me a sense of the sort of geometry of this.

46:20So you've got a black hole in the middle, I take it, which is, well, they don't really have a size, but they... Small, yeah.

46:28So there's a lot of mass in the middle, and then around that you're saying there's hydrogen in various forms. Yeah, so the size of the system, roughly, that we're thinking of is about a thousand times the distance between the Earth and the Sun. So it is very large. It's a big fuzzy ball. Yes, it is not at all... This is why I say it doesn't look like a normal star, right? Like the Sun, we just had the solar eclipse, and we could all see the Sun looks like a perfect, you know, circle until the Moon passes in front and you see some fuzzy stuff on the edges.

46:58This would be, like, a way scaled-up version and becomes very... It's this big blob of gas that becomes much more unstable and much more dynamic. And this hydrogen is falling in on the black hole, and that's what's sort of causing the heat, is that right? That is roughly our hypothesis. It's actually very hard to truly know what's going on on the inside, and because the dense gas you have to think of as kind of a very thick blanket or a very, like, thick curtain that is obscuring our view of what is happening on the inside of this source.

47:32Oh, so what you're seeing is, as it were, the shield around the outside of it. Exactly, yes. You can't see directly the action. No, we cannot pierce through or... And so, actually, some people have said that maybe there's not even a black hole at all at the centre, and maybe we are actually looking at just a giant star, what we call a supermassive star. Those have been proposed theoretically before, but never observed. But you're seeing this cloud of hydrogen gas outside, which is what? That's absorbing the heat from inside and then re-radiating it, and that's what you're getting, a sort of secondary effect.

48:05Yeah, so, yeah, how we call that in practice is we call it reprocessing. And so, yeah, there are high-energy photons at the centre, and then it gets scattered through this gas, and as it does so, the light essentially gets reddened. Right. Give me the sense of the scale of the thing, the size. What about the mass? I mean, how much, what kind of a black hole is it at the middle of it all, do you think? That is a very good question. I mean, you truly do not know. So, currently, the estimates range all the way from 1,000 solar masses to 100 million.

48:40Wow. And so, that's quite... So, really, it's astronomers saying, we have no idea. But, of course, you need to remember that you have, if you have an accreting black hole there, that material will get consumed very rapidly. And so, you do need some sort of larger reservoir likely to sort of sustain this object if it lives longer. I mean, these dots, are they in galaxies? Because this is a time when the first galaxies are being made. So, are they associated? Are they in galaxies? Are they like the black holes that we have ultimately, you know, in our own galaxy,

49:12the supermassive one that we have in the middle of ours, and you see another galaxy? Yeah, that is another important of a question. And so, there has been speculation on whether, you know, this could be actually the host galaxy that this source lives in. But it means it's a very small galaxy. And so, we think this has to be associated with a very early phase of galaxy formation. What I'm trying to work out is, are they a peculiarity of the early universe, which then goes away? Are they part of the normal evolution of the universe?

49:46Are they related to the way that stars and galaxies later go on to evolve, the way we see them sort of much closer to us? Are they oddities or are they an important part of the story? Well, the fact that they are so common, you need to remember this is a phase, right? And so, if at time of observation, so now we see 2% of all sources are little red dots, and this is a phase that we think is maybe 10 to 100 million years, then it means that, you know, many, many more galaxies, like a large fraction of the entire population has to go through it.

50:17And so, it is a peculiarity in the sense that we had not seen it before. But actually, it must be very common in galaxies in general. The question is what it actually means, right, for galaxy formation. That is a separate question. The jury is still out. I think one of the most exciting possibilities, and I think that's also where a lot of excitement in the community comes from, is the fact that we could be witnessing, essentially, the birth of the central black hole of galaxies. Like, you know, the Milky Way has Sagittarius A star, which is a million solar masses, and we don't know when that formed exactly.

50:50And so, we could actually be witnessing sort of, you know, the hearts of galaxies information in the very early universe. And that is exciting, because we actually don't know where supermassive black holes come from. This has been a major open question for decades. And so, this could be a very important piece of the puzzle. Absolutely. I mean, that's what I was wondering, because if you're just starting out with a soup of sort of hydrogen that's been invented in the Big Bang, it's got to clump up and come together somehow to make both the black holes and stars. You're saying that this could be part of the process

51:21of how the first big black holes were building themselves. Yeah. So, we see, at least in the nearby universe, we see that most galaxies have a supermassive black hole in their center. In the early universe, we also see actually supermassive black holes quite commonly. And there has been a longstanding question of how do you form, you know, such a massive black hole, actually, especially in the early universe, in not a lot of time. And so, the little red dots come in in two ways, really.

51:51On the one hand, it provides a mechanism to form what we call the seed. This can be in a few different ways. One of them is a direct collapse of like a gas cloud, but there are other mechanisms you can imagine. And then the second is that because it is wrapped up in this dense gas, we actually also think that it corresponds to a phase of very rapid growth. And so, not only do you form the seed, but you also have this period of very, very rapid growth that will get you to a more massive black hole. What I'm getting from you is you've got some absolutely intriguing clues

52:22that point to some pretty solid facts, but there's so much detail you still want to work out. For sure, yes. It's a fun puzzle. I mean, there are a lot of open questions. We spent the past few years really, first of all, ruling out what these sources are not. And I think we've now reached a stage where we have proven that we are looking at a new class of objects. And only then can you take the next step and really start to ask these detailed questions. So, yes, there is an exciting couple of years ahead. That's brilliant.

52:53Anna de Graaf, thank you so much for talking to us. Thank you. Anna de Graaf is an astronomer at the Max Planck Institute for Astronomy. This show would not be possible without its luminous stars, senior producer Gary Niederhoff, producers Brian Edwards and Shannon Rose Geary,

53:25and consultants Sikon Akbon and Roland Pease. I am the executive producer of Big Picture Science, Molly Bentley. And I'm astronomer Seth Shostak. We'd like to give a big thanks to our listeners and to our Patreon supporters. The original music in the show is by Dewey DeLay and June Miyake. And this episode of Big Picture Science that examines how a remarkable new telescope may change our view of the cosmos is called a coup de grace in space. Looking to get the most out of your money,

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