JWST Found Something New- Black Hole Stars

Astronomers have discovered a brand new type of object and they found it by accident. In a search for the most distant galaxies in the deepest images taken by JWST, astronomers spotted this, an oddly red and impossibly bright spot. It was so intriguing that they paused their original search to look further and deeper into this unsuspecting speck and what they found was something very exciting, that this thing was humanity's first discovered black hole star. Hi, I'm Dr Kirsten Banks, Astro Kirsten, if you will. I'm an astrophysicist and self-proclaimed space yapper and this nature paper that dropped recently has had me obsessively learning about black hole stars since I learned about the discovery. So let's dive into it together. First, we'll explore what exactly is a black hole star. We'll follow that with the journey that got us here. Then we'll dive into the guts of this latest research before ending on what this could mean for all the little red dots JWST has discovered since its first light. So come with me and let's explore the universe together. Okay, but what even is a black hole star anyway? The short answer is it's an object that looks like a star on the outside but in its core, instead of a typical stellar core where nuclear fusion happens, there is a black hole. Okay, but how does that even work? How does the black hole at the centre not just slurp up all the star stuff around it? And why is this even a thing? These are all great questions that we'll answer together now. First, I want to take us back to the origins of black hole stars. These objects were first hypothesized back in 2006. Back then, they were referred to as quasi stars and they came about as a possible solution to the mystery surrounding how supermassive black holes, the ones at centres of galaxies, get so dang big so quickly in the universe. Researchers proposed that in the early pristine universe, massive clouds of gas, specifically protostars, could reach 1,000 to 10,000 times the mass of the sun. In today's universe, a star of a mass like that would certainly explode in a supernova. But in the early universe, it was hypothesized that the outer layers could be massive enough to absorb that supernova explosion. So then, instead of the star blowing apart, its core would collapse into a black hole while the rest of the gas remained trapped by gravity, forming the quasi star configuration, or a star-like object with a black hole core. Within this framework, these objects are considered the teenagers or progenitors of the billion solar mass monsters we see in the universe at the centres of galaxies today. Okay, sure, so that's what they are and how they're proposed to form. But how does the black hole core not just slurp up everything that's around it? That's actually really fascinating. Think of your typical black hole. It's a dense region of space with so much matter stuffed into it that nothing, not even light, can escape. And as stuff falls towards a black hole, it gets slurped and stretched by the black hole. That is, it gets spaghettified and falls into a disk swirling around the black hole. This is called the accretion disk. Now, this is where people get confused about black holes and their ability to suck everything in because that's not entirely true. Plenty of material that falls towards a black hole never actually makes it past the point of no return called the event horizon. That's because the accretion disk itself is very energetic and can kind of fight against the gravitational pull of its black hole. As stuff falls towards a black hole, it spins around its accretion disk, getting very hot and also very bright. That heat and light have enough energy to generate a radiation pressure that fights against the gravitational pull of the black hole itself. Because of this pressure pushing outwards, there's actually a limit to how quickly a black hole can eat. It's called the Eddington limit. So in the case of a black hole star, it operates in a similar way to how a regular star operates, where the nuclear fusion in the core generates a radiation pressure pushing outwards against the gravity of the rest of the star. But instead of nuclear fusion generating this radiation pressure, it's the black hole's accretion disk that derives that outward pressure. However, there is an extra layer of complexity. For these objects to form, the outer layers of gas, the star part of the black hole star, must be massive enough to absorb the burst of energy from the initial black hole formation without being blown away or immediately falling in. They are truly remarkable hypothetical objects. But with MOMBH star 1, maybe it's our best candidate yet for these hypothetical objects. MOMBH star 1 is unlike any other object seen before and is best described as a black hole star. But how did we get here? We've covered the origin of the hypothesis around black hole stars, but how do we actually come to find one? That's thanks to our favorite Christmas present, JWST. Since its launch on Christmas Day in 2021 and official science operations since about mid-2022, JWST has been revealing more and more of the universe to us. It is responsible for discovering 10 of the furthest known objects in the universe so far, and it's also responsible for one of the biggest mysteries of the universe discussed today, the case of the little red dots. These are exactly as I've seen. Little, compact, and extremely red dots scattered across JWST's deepest images. They were even present in one of JWST's very first images, Webb's first deep field. Now, only JWST could reveal little red dots, not just because it can see back to when they existed, around 600 million to 1.6 billion years after the Big Bang, but because, unlike Hubble, which can also see that far back, it captures the infrared light they actually emit, rather than the visible light that they barely produce. Now, since the first little red dot was identified, JWST has spotted hundreds more, and their origin has caused quite a stir in the astrophysics community because it's not entirely clear what they are exactly, except maybe now we have a clearer picture, which we'll get into more in a moment. Now, despite the differences in their potential explanations and origins, from high-mass galaxies to accreting supermassive black holes viewed as red quasars, or, as is the case of MOMBH star 1 black hole stars, they all have a few things in common. They appear as unresolved, point-like specks, kind of like a star, but not. They all experience a sharp drop-off in light known as a Balmer Break, where the object's brightness just completely disappears below a certain wavelength. And, of course, they're extremely red. Now, quick science aside, what is the Balmer Break? Now, the Balmer Break is this clear drop in light seen in an object, and it happens at one very specific wavelength, 364.5 nanometers. Now, this is where hydrogen atoms gain enough energy to make their slightly energetic electron in the second energy level completely escape the hydrogen nucleus. Below that wavelength, photons have enough energy to strip electrons away completely, so they get absorbed almost entirely. Above it, they mostly pass through. And the result of that is a sharp cliff in brightness at exactly that point, the required energy to blast away those electrons. And more to that, how steep that cliff is depends on the temperature and density of the gas doing the absorbing, which is why it doubles as a diagnostic. Measure the size of the break, and you're measuring the conditions of whatever's producing it. And that's part of the reason why MOMBH1 can't feasibly be anything but maybe a black hole star. So now let's dive deep into the discovery of MOMBH1. Why? Because it's interesting, and I've been obsessing over this for weeks since the research dropped. And I have to let that out somewhere. And this is as good a forum as any. Now, the best part about this discovery for me, apart from the fact that it's insanely cool to find something new in space, is that it happened by accident. The team that found MOMBH1 weren't looking for these once hypothetical objects. They were simply looking for the most distant galaxies in the universe revealed by JWST as part of the survey Mirage or Miracle. But while scanning the deepest JWST images for those most distant galaxies, the team were shocked by this extremely red and impossibly bright little red dot. It was something they just couldn't ignore. And so they took the most epic science side quest and looked into it further. And here's what they found that led to the relatively inescapable conclusion that this impossible little red dot is very likely the world's first discovered black hole star. Their first clue was in the nature of the Balma Break. For MOMBH1, the Balma Break is astonishingly strong and stronger than anything we've seen before. And that led to the relatively inescapable conclusion that the light from MOMBH1 does not come from a population of stars, but instead from a single source of light. The second clue comes from its shape and a few more hidden features in the light pattern or the spectrum of MOMBH1. Now, the fact that they couldn't resolve this object below a size of about 300 light years means it's definitely very small, or at least smaller than a galaxy. In reality, it's a massive, massive star-like object, but let's not get too ahead of ourselves just yet. There's more science evidence to get through. Now, in addition to this point source nature of the object, subtle detections of forbidden transitions, that is, very unlikely transitions like those seen in oxygen atoms, and hints of variability within the object are also characteristics of a feeding supermassive black hole, further leading the researchers down the path of suspecting that this object is driven by a supermassive black hole actively feeding on a lot of stuff. With those two clues in mind, the strong Balma Break and this activity indicative of a supermassive black hole, the researchers went and ran some simulations to try and kind of recreate these observations, and remarkably, they found a pretty significant match. The spectrum patterns of MOMBH1 are best matched by a supermassive black hole about a million times the mass of the sun, surrounded by a thick shell of gas like the outer layers of a star that has a thickness similar to the distance between the sun and Pluto. So this thing is roughly the size of our solar system. That's insane. So what does this discovery mean for all the other little red dots discovered by JWST? Well, for one, it gives astronomers a way to stop treating each little red dot as its own separate mystery. Before this, they were quite the mess to explain. They were all objects that looked like a tight, compact point in red light, but stretched out and fuzzy kind of in blue light, with none of the signs of dust that you'd expect from something that red. What MOMBH1 does offer is a simple fix. Little red dots aren't just one object, there are two, layered on top of each other. A black hole star dominating in red light, sitting inside an ordinary star-forming galaxy that supplies that blue light of little red dots. It also forces a recheck of every black hole mass estimate made from objects like these. Astronomers had been sizing up these black holes using the width of their hydrogen lines, which works just fine for nearby and normal black holes. But if that light is bouncing around a dense gas of stuff before escaping, rather than moving at the speed of the orbiting gas, the lines get artificially stretched out. And that means a lot of impossibly oversized early black holes might not actually be so oversized at all. Some mass estimates could be off by factors of up to 100. Which also means the fear that early black holes broke our models of galaxy growth may have been based on a measurement problem, not a real crisis in cosmology. That is certainly exciting. And beyond all that, there's the claim that if this gas-shrouded, fast-feeding phase is a normal stop along the way to becoming a supermassive black hole, then every giant black hole we know of today, including the one at the center of our Milky Way galaxy, may have gone through exactly this stage once in their lives. That's the open door this discovery leaves behind. Is MOMBH-1 a rare find? Or is it the first clear picture of a phase that every supermassive black hole goes through? Answering that means finding more of them. More little red dots with spectra detailed enough to check for the same gas signatures at different points in cosmic history to then see whether this really is a universal chapter in the story of every black hole, or just one strange object that got lucky enough to get caught in the act. Either way, this feels big. And definitely worth the Nature publication. So congratulations to the research team. You spotted something weird. Followed your curiosity. And now we have more to look forward to. Our universe is just weird and wonderful. And there is so much to uncover. Thanks for sticking around. If you want more cosmically curious space stories, I have a book coming out very soon that is full of them. It is called Lost in Space. It's available now for pre-order. And I can't wait for you to read it. I spent so much time on this and I'm so glad I can finally tell the world about it. I'll leave you information about how you can pre-order it in the description. But as always, stay curious and keep looking up.