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Then they talk about the blue giants exploding and spreading newly created elements everywhere to form other stars. Well, why didn't those stars create "black holes". That's what is supposed to happen when a star beyond a certain mass is supposed to create. At least, that's what they say in other programs discussing nonexistent black holes.
Plus, when the star exploded it scattered all of its atoms everywhere. How was gravity supposed to pull everything back together into a proto solar system.
The main problem I have with the computer imagery is that they are showing thick clouds when space is essentially a vacuum. How did rocks form out of gas to then smash together and form a planet, etc...
We would need to go minute by minute through the video, asking how they know what they are saying, and why are they missing such obvious things like the fact that "Dark matter" has never been shown to exist.
They have all those great computer graphics showing faint structures as if the human eye could see them, yet when they show the Sun they don't show the vast unseen electrical structures that is actually powering it.
Read the Bethe paper on the Sun that I have up thread and you will see that he simply made up how "fusion" in the core powers the Sun.
The only thing in the whole program that was "fact based" is the Parker Solar Probe, yet the computer imagery of it is pure fantasy.
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- Joined: Sat Aug 23, 2008 12:51 am
The only things of "fact" that the episode has is the Hubble telescope, and the Gaia satellite, everything else is made up.
BTW, is it just me, or do these people look like children. Why are there no old astronomers anymore.
NOVA Universe Revealed: Milky Way
https://www.pbs.org/wgbh/nova/video/nov ... milky-way/
PREMIERED NOVEMBER 3, 2021 AT 7PM ON PBS
Straddling the night sky, the Milky Way reminds us of our place in the galaxy we call home. But what shaped this giant spiral of stars and what will be its destiny? NOVA travels back in time to unlock the turbulent story of our cosmic neighborhood, from its birth in a whirling disk of clouds and dust to colossal collisions with other galaxies. Finally, peer into the future to watch the Milky Way’s ultimate fate as it collides with the Andromeda galaxy, over 4 billion years from now.
Universe Revealed: Milky Way
PBS Airdate: November 3, 2021
NARRATOR: The Milky Way, our home, formed not long after the Big Bang, one of trillions in the universe. This is our galaxy, billions of planets orbiting billions of stars. We are only just beginning to understand its true place in the universe.
GERRY GILMORE (University of Cambridge): It was only a hundred years ago, people thought our Milky Way was the entire universe.
PAYEL DAS (University of Surrey): If we really want to understand where we come from and how the galaxy was formed, we can’t just look in our cosmic, sort of, backyard. We need to look much further afield.
NARRATOR: And when we do, we discover a universe in turmoil…
VASILY BELOKUROV (University of Cambridge): Our history is made up of multiple collisions and interactions with our neighbors.
RANA EZZEDDINE (University of Florida): Our Milky Way is not static. It is dynamic, and it had such a rich, dynamic history.
NARRATOR: …and our place in it, far from secure.
DAVID ROSARIO (Newcastle University): A collision can change the structure of a galaxy, reorders the stars, and so, you end up with something that looks different, that behaves differently.
NARRATOR: Now, we can see our galaxy’s future and its inevitable end.
JEN GUPTA (University of Portsmouth): The Andromeda galaxy is actually heading towards us at about 250,000 miles per hour.
GERRY GILMORE: It will be a really nice sight, actually. Just watch it coming, I mean, there’s nothing we can do about it except sit back and enjoy the view.
MICHELLE COLLINS (University of Surrey): It’s all coming together to tell us about how we got here and what our place in the universe really is.
NARRATOR: The Milky Way, right now, on NOVA.
Above us in the night sky, visible all around the world, the Milky Way wraps its arms across the sky, a band of stars like no other.
GRANT TREMBLAY (Center for Astrophysics | Harvard & Smithsonian): When the Milky Way is up overhead, the skies are so brilliantly bright that I swear the band of the Milky Way, the disk of our own galaxy, quite literally casts a shadow.
MICHELLE COLLINS: Our Milky Way is this really incredibly beautiful place. It’s this wonderful collection of beautiful stars, gas and dust that all kind of swirls together, almost like an abstract painting.
PAYEL DAS: We’ve been trying to understand the band of stars that stretches across the night sky since the time of the ancient Greeks.
NIA IMARA (Astrophysicist): Humans have been looking up at the night sky since the dawn of time, because we want to know what’s out there.
NARRATOR: Because the story of our galaxy is the story of every one of us.
GERRY GILMORE: How does it all fit together? What are we part of? Can we understand it?
NARRATOR: The Milky Way galaxy takes its name from the dense band of stars that we see from Earth, when, in fact, it’s a structure that entirely surrounds us. Every star in the sky, is part of it, including our sun.
SOWNAK BOSE (Center for Astrophysics | Harvard & Smithsonian): When looking into the night sky, you would see this band of stars stretched across it, which actually corresponds to the disk of the Milky Way. So, we actually live inside the Milky Way.
RANA EZZEDDINE: Our galaxy is a spiral galaxy. And we can build up this picture, which we have been doing for hundreds of years, so far, since the first astronomers, like Galileo, to, kind of, build up this beautiful picture of our Milky Way.
PAYEL DAS: Right in the center you have a bulge, then you have a pancake-like structure. That’s the disk, and that’s where we are. And then further out, you have a faint halo of stars that goes quite far beyond the disk.
MICHELLE COLLINS: It’s this beautiful spiral structure of hundreds of billions of stars, all orbiting around a supermassive black hole, right at the center of the galaxy.
NARRATOR: The Milky Way’s complex structure has taken billions of years to evolve, and yet, it’s one of the most familiar forms in nature.
GERRY GILMORE: So, let’s start at the very center. And, in the center, there is a very old bulge, that contains most of the old stars. And this is the remnants of the first stars that formed in our part of the universe. Right at the very heart of it, there is a supermassive black hole. That is the core of the Milky Way, as we know it. And then, around that’s the bulge, then there’s this big bar structure, mostly old stars. And that’s what drives the spiral arms.
So, we can then say, “Where are we in all of this?” We know pretty well where the sun is and, hey, presto, one sun. And it will be about there: roughly halfway from the center to the outer spiral arm structures. And this is where the sun lives today.
NARRATOR: The Milky Way’s elegant spirals are the signature of its dynamic history. The challenge is how to observe it and tease out that history, from our position on the inside.
MICHELLE COLLINS: One of the problems of trying to study the Milky Way from our position here on Earth is that it’s really hard to get a sense of what the galaxy looks like, overall.
PAYEL DAS: So, if we really want to understand where we come from and how the galaxy was formed, we can’t just look in our cosmic, sort of, backyard. We need to look much further afield.
NARRATOR: Clues to how the Milky Way formed and evolved emerged in the 1990s, with the launch of the most ambitious space telescope at the time.
HUBBLE SPACE TELESCOPE MISSION CONTROL: Five, four, three, two, one, and liftoff of space shuttle Discovery with the Hubble Space Telescope, a window on the universe.
Standing by for separation. Solid rocket boosters have separated.
PAYEL DAS: The Hubble Space Telescope is one of the greatest feats in space missions of human history.
GRANT TREMBLAY: This 2.4 meter piece of glass, we turned it on our universe and it has enabled untold advances.
NIA IMARA: Images from Hubble transformed astronomy, transformed science.
NARRATOR: Hubble isn’t just focused on the Milky Way. It also looks beyond, much deeper into space.
DAVID ROSARIO: The data from Hubble is unsurpassed. It gives us the sharpest views of galaxies and the distant universe.
PAYEL DAS: Hubble’s a little bit like a time machine. It’s able to pick up light from galaxies that come from very far away. And because they’ve come from very far away, we’re looking at them in completely different time, far back in time.
NARRATOR: To look far back in time, Hubble trains its gaze on one tiny blank patch of sky, for over 11 days.
PAYEL DAS: What appeared was pretty incredible.
RANA EZZEDDINE: We were able to see galaxies in this ultra-deep field that is farther away than we’ve ever, ever looked.
PAYEL DAS: So, it’s really given us an idea of how many galaxies are out there and the variety of galaxies out there.
GRANT TREMBLAY: It’s a very hard number to estimate, but it is absolutely in the trillions. Their morphology can be incredibly complex, big train wreck mergers or absolutely stunningly beautifully round, grand design spirals and everything in between.
NIA IMARA: There are starburst galaxies that are generating new stars at prodigious rates. And there are small galaxies, which are my favorite. We call them dwarf galaxies. And they may be thousands of times less massive than the Milky Way, but they’re actually the most common galaxy in the universe.
NARRATOR: Hubble tells us there are trillions of galaxies in the universe. And by focusing on the ones that are farthest away, it looks deep back in time, giving us a picture of what galaxies look like in their infancy.
And they started forming in an era of immense cosmic activity, not long after the universe began. Before the Milky Way forms, space is filled with a vast structure known as the “cosmic web.” Hydrogen and helium gas collect along the web’s vast filaments, but the web itself is made from something more mysterious. It’s called “dark matter.”
DAVID ROSARIO: Dark matter is something that has gravity but produces no light. It surrounds us, in fact, it dominates the mass in our own galaxy, and yet we don’t know what it is. We can’t touch it, we can’t feel it.
MICHELLE COLLINS: Galaxies really need dark matter, because it’s, kind of, like, the glue that binds them all together. You can almost say it’s like the seed of galaxy formation. It creates these huge structures into which ordinary matter falls, and then that matter all gets compressed and can turn into stars. And that really is, then, what seeds galaxy formation, as a whole.
NARRATOR: The first stars are born where the filaments cross and dark matter is at its densest, drawing large amounts of gas together, until it collapses under its own gravity, causing stars to ignite. New stars, in their billions, are bound together by gravity, orbiting a common center.
These are the first galaxies, among them, the Milky Way, in its embryonic form, a whirling disk of gas and stars surrounded by an invisible halo of dark matter.
Across the universe, hundreds of billions of galaxies are forming. Some, a few dozen, are born very close to our own Milky Way. Over time, gravity draws these galaxies ever closer, to form what we know as the Local Group.
RANA EZZEDDINE: Our Local Group is a set of galaxies that lies in a volume of the universe that we believe is gravitationally bound together, meaning that these galaxies are close enough that at some point they might all combine together or collide together to form one big, large galaxy.
MICHELLE COLLINS: The galaxies within the Local Group can all feel one another’s gravity, so they’re all, sort of, slowly moving together, with time.
NARRATOR: Just three-billion years after the Milky Way began, it rises in the night sky of its first planets, but with only half the stars and a more irregular structure than the mature galaxy we see today.
So, how did our galaxy get its spirals? To answer the question, a new spacecraft is built. “Gaia” will look directly at the Milky Way itself.
Its designers are determined to overcome an age-old problem: how to measure the true distance between stars.
GRANT TREMBLAY: Being able to determine the distance to objects is one of the most fundamental things you need to do to understand the structure of our universe.
NARRATOR: To measure the distances accurately, Gaia’s engineers must devise an orbit for the craft, big enough that it can measure the same star from two points, very far apart, called a “parallax” measurement. Gaia will need to travel almost a million miles from Earth.
GAIA LAUNCH ANNOUNCER: Attention pour la décompte finale. Dix, neuf, huit, sept, six, cinq, quatre, trois, deux, un. Top. Décollage!
GERRY GILMORE: I’ve been involved in Gaia since the very beginning of it. It was a beautiful launch, really spectacular.
NARRATOR: The spacecraft shares the name of the ancient Greek Earth goddess, Gaia.
GERRY GILMORE: It took four minutes. You could see the flame of the rocket, and you could see the individual stages popping off. Then, they got into this critical state, where they had to open up the sun shields.
It was critical that this opened up and protect the payload from the sun. And that was the “do-or-die” moment.
NARRATOR: Gaia’s mission is to map the true positions of a billion stars in our Milky Way, nearly all of them for the first time.
VASILY BELOKUROV: Before Gaia, we just looked at the images of our galaxy, we were missing half of the information.
GERRY GILMORE: Gaia is the first ever precision distance measuring machine that mankind has ever had.
NARRATOR: So, how is it possible for Gaia to map the Milky Way so accurately from within?
First, it travels to its distant vantage point called L2; a gravitational sweet spot. It can hold here, with minimal fuel use, as it follows the earth in its extensive orbit around the sun.
DAVID ROSARIO: Astronomy has always been at the forefront of technology, but the kind of technology we work with right now is absolutely amazing.
NARRATOR: With just a whisper of nitrogen, to help Gaia’s telescopes sweep smoothly through 360 degrees, four times a day, it makes over one-and-a-half-million observations an hour.
After four months, it has looked at the whole sky at least once.
Gaia gathers data on the brightest stars across the whole sky, stars within the disk of the galaxy, from the center to the halo and beyond. After it has travelled millions of miles in its orbit, it observes the same stars from a different vantage point. After nearly two years of almost non-stop sky-scanning, scientists can triangulate the true position of over a billion stars, for the most accurate map of the galaxy ever created, the Gaia map.
VASILY BELOKUROV: The Gaia data has allowed us to see our own galaxy like never before.
RANA EZZEDDINE: I think that Gaia opened up a really new axis of information to us that we just have never imagined it would do.
GRANT TREMBLAY: These are like having completely, you know, revolutionary cartographers make an entirely new map of our home galaxy.
NARRATOR: Finally, astronomers have their Holy Grail: the Milky Way, mapped in three dimensions.
GERRY GILMORE: This is the first ever honest 3D picture of the Milky Way. It’s not a simulation from a computer and it is not an attempt at guessing the structure from approximate data. Every one of those stars is individually measured to high precision.
So, this means that we can move ourselves around, through this, and see, well, what does this bit of the Milky Way actually look like? And you decide you want to look at it from far away and you can do that, or you can zoom in close and say, “I want to know how that star cluster works. I’ll go and sit inside it.”
Gaia can tell the difference between a star that’s at the front of that cluster and the star that’s at the back of that cluster, even though the cluster itself is 5,000 lightyears away. Gaia is not only measuring where things are, to delightful precision, but, equally, you can see things moving. And it’s actually the moving that’s the critical bit.
NARRATOR: In addition to mapping stars in three-dimensional space, Gaia captured another dimension, the result of its repeated trips around the sun: time.
This data could help us understand how our galaxy evolved.
DAVID ROSARIO: Gaia doesn’t just tell us where the stars are in the sky, but also how fast they’re moving across the sky and towards us. And that’s an essential bit of information to understand how things change over time.
NARRATOR: Once scientists know how a star is moving, they can use Newtonian mechanics to calculate where it is going. And, using the same calculations, they can reverse the motion of the star to uncover where it has been.
This new data is revolutionizing a field of science known as “galactic archaeology.”
DAVID ROSARIO: Galactic archaeology is the process of identifying the history and the motion of stars, so you can figure out where stars come from, how old they are and how their motions change over time.
PAYEL DAS: What’s been really incredible about Gaia is, if we couple it with spectra that we’re observing back on Earth, we’re able to date the stars and really use them as the fossils that they’re supposed to be. So, this means we can work out what the fossils tell us about the evolutionary events that happened in the Milky Way’s past and then date them, so put them in chronological order.
RANA EZZEDDINE: So, we combine everything together in order to get a really clear understanding of how the Milky Way came to be.
NARRATOR: This new data from Gaia has helped scientists spot a pattern between the Milky Way and our neighborhood cluster of galaxies, the Local Group.
PAYEL DAS: The important thing to know about our galactic neighbors and the Local Group is that nothing’s actually sitting still. Gravity means that we’re all moving towards or away from each other and we’re sort of playing a dance out there.
NIA IMARA: Gravity is the great cosmic attractor.
VASILY BELOKUROV: This dance of the galaxy and its neighbors have been going on for billions of years.
NARRATOR: Gaia is only just now revealing the steps to this intricate intergalactic dance.
SOWNAK BOSE: When the Gaia satellite started producing its data and astronomers started analyzing this data, there was something rather curious.
MICHELLE COLLINS: A large sample of stars were found that seem to be rotating in the opposite direction to the majority of stars in the Milky Way disk. And that’s really unusual. And it was really surprising.
GRANT TREMBLAY: So, that means that not all of the stars that make up our galaxy, the Milky Way, were actually born here.
MICHELLE COLLINS: They probably came from a different galaxy altogether. So, they’re almost these alien stars that have been brought in.
NARRATOR: Gaia’s data led scientists to make an astonishing discovery.
DAVID ROSARIO: So, the most mind-blowing thing is that those stars are the remnants of a humongous collision, and they actually come from another galaxy.
NARRATOR: If we could travel back in time 10-billion years and land on one of the earliest planets within our Milky Way, we’d see something spectacular in the night sky: billions of stars coming into view, heading towards us. The Milky Way is about to collide with another galaxy from our Local Group, called “Gaia-Enceladus.” A quarter of the size of our galaxy, Gaia-Enceladus is drawn into the Milky Way, bringing disorder to its flat disk.
GRANT TREMBLAY: When you look at a galaxy merger, it looks like an incredibly violent process. But it’s actually something that’s incredibly elegant, and that is because galaxies are ultimately mostly empty space. And so, when galaxies collide or crash together, they pass through one another like ghosts. The chance for a star-star collision in a galaxy merger is actually exquisitely low.
SOWNAK BOSE: It’s really quite a beautiful process, because the way in which the mutual gravity of these two galaxies actually interact with one another causes one to start, sort of, spiraling around. Once it plunges in, it spirals around it and then comes back and returns. So, it’s kind of like, you know, two objects in a, sort of, celestial ballet, around one another.
DAVID ROSARIO: A collision can change the structure of a galaxy, reorders the stars, and the galaxy gives them new orbits, move the gas into different places in the galaxy. And so you end up with something that looks different, that behaves differently.
NARRATOR: The invisible driver of all these interactions is the same stuff that formed the galaxies in the first place: dark matter.
DAVID ROSARIO: Because it accounts for most of the gravity in the galaxy, it is dark matter that determines how violent the collision is, how rapidly and with what intensity galaxies come together when they collide. In many ways, it determines how galaxies end up after a collision.
NARRATOR: Just a few billion years after the Milky Way formed, already much more massive than Gaia-Enceladus, the Milky Way’s gravity overwhelms its neighbor, absorbing it entirely. The Milky Way is bigger by a billion stars.
DAVID ROSARIO: For the first time ever, we have seen how our Milky Way has grown bigger.
MICHELLE COLLINS: What we’ve learnt from this collision is really about how much richer our galaxy grew, but it doesn’t actually tell us about us yet.
NARRATOR: To find out how our solar system got here, scientists have been tracing the history of another unusual group of stars. They loop around our galactic disk in a spectacular trail called the “Sagittarius stream.”
MICHELLE COLLINS: So, the Sagittarius stream is really interesting, because it might actually help us understand where we came from.
SOWNAK BOSE: It is what’s known as a tidal stream, which is a stream of stars that have been stretched across the night sky due to the gravity of the Milky Way.
RANA EZZEDDINE: The Sagittarius stream is so big that it goes all the way up and even all the way down, so we can just carry the Milky Way from its handle. It’s really, really large stream.
NARRATOR: The trail of stars we see today is named after the galaxy that they used to belong to, “Sagittarius dwarf.”
GERRY GILMORE: The Sagittarius galaxy was discovered by a student and myself in the 90s. Most of the Sagittarius galaxy is actually spread out in two streams, one in front and out the back, like giant comet tails wrapping around the entire sky, going out for maybe 100,000 lightyears away. We could see these, but it wasn’t possible to understand how they got there.
Now, with Gaia, we have the motions of these stars, so we can see what direction they’re moving in, which ones are going fast, which ones are going slow. For the first time ever, it’s been possible to say, “Ah, this is what happened.”
SOWNAK BOSE: The Sagittarius stream is essentially the tidal debris that has been left over when a dwarf galaxy, the Sagittarius dwarf actually, plunged into the Milky Way.
NARRATOR: By studying the stream of stars, scientists have uncovered the story of a much more recent galactic collision, this time with a much smaller galaxy.
GERRY GILMORE: When the Sagittarius galaxy orbited into the Milky Way, it came, foolishly, rather far in.
NARRATOR: As it dives toward the Milky Way, the dwarf galaxy begins to have its stars pulled off.
GERRY GILMORE: When it goes through the disk, it punches a hole in the disk, and the stars get put in this particular patterns, and it’s got stretched into these two great long streams.
NARRATOR: The much smaller galaxy encroaches upon the Milky Way, just like Gaia-Enceladus did. But the timing is intriguing, because this collision happens just before the birth of our own solar system.
GRANT TREMBLAY: One of the most important consequences of galaxy mergers, like the destruction of the Sagittarius dwarf galaxy by the Milky Way, is a new, fresh injection of gas into the galaxy, right? And it is gas, particularly cold gas, that is the fuel from which all stars are born.
PAYEL DAS: For star formation to occur, basically, the colder the better.
NARRATOR: The most important gas that the collisions bring is made of one of the oldest and most ubiquitous elements in the universe.
DAVID ROSARIO: So, what I’m listening to here is the lifeblood of our galaxy, hydrogen. We can detect it with our radio telescopes, like in this case, pointing right at the Milky Way. Hydrogen is the most common element in the universe, and it’s in our own galaxy.
We don’t see gas with our eyes, and therefore we are not used to the idea of there being plenty of gas in the Milky Way. But if you use a radio telescope, you can see it. You can look at the radiation coming from that gas, and that’s exactly what we’re doing right now.
This gas is connected to stars deeply. It’s what stars form from. If this gas wasn’t there, stars would never have formed.
NARRATOR: Hydrogen was created shortly after the birth of the universe, and it has always been spread throughout the Milky Way, but not evenly. It clumps together in dense clouds that, in this iconic image, extend up to 30-trillion miles. Scientists call them stellar nurseries, where temperatures are low enough for gas to condense.
NIA IMARA: Stellar nurseries are some of the largest, coldest and certainly among the darkest regions within any galaxy. If you were to fly through a stellar nursery, it would be extremely cold and extremely turbulent and chaotic place, pervaded by magnetic fields and charged particles streaming throughout.
It might be glowing a little bit, and as you approach closer and closer, you would realize that it’s actually heating up a bit. It’s actually becoming warmer. You would perhaps surmise that this is where a new group of stars is being born.
MICHELLE COLLINS: Hydrogen can be thought of as the lifeblood of galaxies, because it’s the first building block of stars. In the center of a star, it’s fusing hydrogen together all the time to produce helium, and that gives off energy, which allows the stars to, sort of, light up.
NARRATOR: When the Sagittarius dwarf galaxy collides with our Milky Way, it brings more hydrogen to these clouds, triggering a new era of star birth.
SOWNAK BOSE: When galaxies interact with one another and they collide with one another, what typically happens is that you actually get a big burst of stars formation occurring, and that’s primarily because you are essentially bringing in a new source of star-forming fuel into the Milky Way.
NARRATOR: This era coincides with the birth of our own sun, 4.6-billion years ago.
PAYEL DAS: The jury’s still out, but we think that the start of the sun could have formed in that first enhancement in star formation.
RANA EZZEDDINE: The timing of the collision between the Milky Way galaxy and the Sagittarius dwarf galaxy coincides with a peak in star formation that we see happen in our Milky Way. And we know that the age of the gas in which our solar system was formed lies very close to this spike in star formation.
GRANT TREMBLAY: It is certainly possible, right, that our own solar system is anchored around a star that was born from gas that did not originate in our home galaxy. It was taken. It was pulled or consumed by the Milky Way, when it ripped apart a satellite galaxy, maybe even the Sagittarius dwarf.
NARRATOR: For a small galaxy, Sagittarius dwarf has had a big impact, and not just by triggering star birth. It plunges back and forth through the Milky Way as the galaxies become enmeshed, which likely contributed to the formation of the spiral arms. But its influence is fast fading.
SOWNAK BOSE: The question as to whether the Sagittarius dwarf galaxy is still around kind of depends on what you, what you, kind of, end up thinking of as being a galaxy after a certain point. It is really a galaxy that is in the process of being totally disrupted. And one day it will end up merging with the center of our galaxy. So, in in some sense, it’s only the sort of memory of the galaxy that is left behind.
NARRATOR: When we look up at the night sky, it’s easy to think of the Milky Way as static, but we now know it’s evolved through a turbulent history of collisions and mergers.
RANA EZZEDDINE: I think that Gaia opened up this whole new vision for us of…that our Milky Way is not static. It is dynamic and it had such a rich, dynamic history.
NARRATOR: But none of it is random. The force that causes galaxies to form, merge and evolve is gravity.
GRANT TREMBLAY: The thing that ultimately sculpts how those galaxies look is gravity. It’s not the collisions. It’s gravity: it’s the stars within those galaxies tugging on one another; and it’s the underlying dark matter, halos of those galaxies, merging together.
MICHELLE COLLINS: So, we’re actually at a really exciting time now in astronomy, because we can tell the story, not only of how our galaxy came to be and how everything led up to now, but we can also start to peer into the future and see what’s in store, what’s yet to come for the evolution of our galaxy.
NARRATOR: The more we learn about the Milky Way and its dynamic history, the more incredible it seems that we ourselves, orbiting just one star among billions, have been able to figure out our galaxy’s story, written in the stars. And we are now poised to map out its ultimate fate.
JEN GUPTA: The Milky Way is no stranger to galactic collisions. As we look around the night sky, we see evidence that our Milky Way galaxy has had these interactions with galaxies before. But what’s coming next is something on an entirely different scale.
This faint smudge of light that you see, right there, in the center of the image, it’s not some condensation on the lens or a cloud in the sky above us, this is an entire other galaxy, a huge galaxy, two-and-a-half-million lightyears away from us. To put that into units that humans can try to understand, this faint smudge of light is about 15-billion-billion miles away.
NARRATOR: This galaxy is called Andromeda and is set to play a defining role in our galaxy’s future.
The Hubble Space Telescope has taken extraordinary images of Andromeda. Compared to the disk of the Milky Way, Andromeda seems tiny, when in fact it’s anything but. It’s our largest neighbor in the Local Group, with the same spiral structure and the same long history of feeding on smaller galaxies.
JEN GUPTA: This image, right here, is actually ridiculous, when you think about it. It’s an observation of part of the Andromeda galaxy, taken with the Hubble Space Telescope, and the level of detail here is incredible. This image contains about 100-million stars that we can see in another galaxy. It’s just mind-blowing.
When we look at it, we start to be able to understand its structures. And what strikes me immediately is that it’s kind of familiar. If you zoom in on the spiral arm, it’s exactly the same as what we see when we look into our own Milky Way. And when we look at the Andromeda galaxy, we see this history, we see that it’s been cannibalizing these satellite galaxies in a similar way to the Milky Way, growing into this beast, this giant that’s a match for our own galaxy.
MICHELLE COLLINS: We now have many beautiful images of Andromeda. We studied it with a huge range of telescopes, and in many ways it’s a lot like the Milky Way, this beautiful spiral galaxy. So, you might think they are going to be very similar galaxies with a very similar history. But what we’ve learnt through studying Andromeda over time is that, actually, they are not quite the same.
NARRATOR: In fact, Andromeda is 50 percent bigger than the Milky Way. And that’s not all.
JEN GUPTA: The Andromeda galaxy is actually heading towards us, at about 250,000 miles per hour. In about four-and-a-half-billion years’ time, that faint smudge of light we saw in the sky will collide with the Milky Way galaxy, changing our galaxy forever.
NARRATOR: The Milky Way as we know it today, is not eternal. And Earth will witness the final act: two galaxies in a single sky, gradually, but inevitably, merging into one.
RANA EZZEDDINE: There is absolute evidence that Andromeda is going to collide with the Milky Way one day, because they are pulling each other closer and closer over time. And one day they will go so close that they will collide.
DAVID ROSARIO: Andromeda and the Milky Way, when they come together, sparks fly.
MICHELLE COLLINS: It’s going to be an incredible time. If we were able to view this collision happening, it would be amazing to watch the night sky change over time.
GERRY GILMORE: Be a really nice sight, actually. Yes, just watch it coming, I mean, there’s nothing you can do about it except sit back and enjoy the view.
MICHELLE COLLINS: We’ll end up smashing these two galaxies together. There may be a huge burst of star formation, initially, which will, sort of, light up the night sky with fireworks. And then, over time, that will burn off all the remaining gas we have in those two galaxies.
NARRATOR: But unlike in previous collisions, this time, our galaxy is the smaller of the two. Andromeda and the Milky Way pull at each other’s spiral arms, scattering stars, until no trace of the original structures remain, two spiral galaxies merged into one colossal mass of stars.
GRANT TREMBLAY: Watching the motion of galaxies is like looking at a really, really exquisite ballet in really, really slow motion. When that dance is finally complete, the structure of the Milky Way will be forever altered.
MICHELLE COLLINS: While this collision will extinguish the Milky Way and Andromeda as we know them, it will also create a whole host of new stars. And around those new stars, there’ll be new planets and maybe another generation of people asking the same questions that we’re asking now: Where have they come from? What’s their place in the galaxy? And what’s going to happen in their future?
DAVID ROSARIO: We will not be able to see the beautiful galaxy that we, that we see right now, but the universe will carry on.
NARRATOR: As we look even deeper into the future, all of the galaxies in our Local Group will eventually merge into one enormous entity, floating in isolation. As the universe expands, the distance between all the galactic groups will increase, and the other galaxies will simply disappear from view.
MICHELLE COLLINS: Knowing that we can, sort of, look into the future, many billions of years and understand what will happen to our galaxies is mind-blowing.
NARRATOR: And all of this, we have determined by looking up at the skies from one, tiny, unremarkable outpost in the Milky Way.
SOWNAK BOSE: Even though we, as humans, have such an insignificant role in the grand scheme of things, there is so much about the vastness of space that we can understand just from our unique perspective, here on Earth.
GRANT TREMBLAY: Earth is a tiny little rock and a really indescribably vast cosmic ocean, right? We are just a tiny little planet, spinning in the void.
NARRATOR: But the story of our night sky is far from being complete, and there is so much more to discover.
DAVID ROSARIO: Is there life in the universe? And has there been life in the universe from the very beginning?
RANA EZZEDDINE: What is dark matter? What is dark energy? How does it affect our universe? Particularly, how does it affect our Milky Way and even our own solar system?
NIA IMARA: We want to know where we come from, we want to understand our origins and our destiny. And also, we just love a good story. We love mystery. And the story of the universe is the greatest story of all.
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NOVA Universe Revealed: Alien Worlds
https://www.pbs.org/wgbh/nova/video/nov ... en-worlds/
This is episode four, about "Black Holes".
Now here is where things get bizarre. Remember in the first episode they talked about blue giants exploding to spew heavy elements across the sky, and they never mentioned "Black Holes". Now, just three episodes later, they are showing those blue giants calmly collapsing into "Black Holes", they don't show them exploding at all, so where did all the matter come from to make our Sun.
BTW, The whole series has shown how far NOVA has become simply disinformation. Beautiful computer graphics that fool the eye into thinking something is real there.
Read the book, Evil Geniuses by Kurt Andersen to see where the disinformation is coming from.
Follow the money.
NOVA Universe Revealed: Black Holes
https://www.pbs.org/wgbh/nova/video/nov ... ack-holes/
PREMIERES NOVEMBER 17, 2021 AT 7PM ON PBS
Take a seat on the ultimate thrill ride to explore nature’s strangest and most powerful objects. Black holes can reshape entire galaxies, warp the fabric of space and time, and may even be the key to unlocking the ultimate nature of reality. A new generation of high-energy telescopes is bringing these invisible voids to light, showing that “supermassives” millions or billions of times larger than our sun lurk at the center of nearly every galaxy, including our own. But what happens if you stray too close to one? And what lies beyond the black hole’s abyss? If nothing can ever escape it, is that the end of the story? Or could they be a portal to another dimension—or another universe, full of black holes? (Premiered November 17, 2021)
Universe Revealed: Black Holes
PBS Airdate: November 17, 2021
NARRATOR: Something is hiding in the darkness, invisible objects of unimaginable power that could hold the key to solving the mysteries of space, time and the universe, itself.
SYLVESTER “JIM”JAMES GATES, JR. (Brown University): To me, a black hole is the greatest exhibition of nature’s mysterious powers.
SUGATA KAVIRAJ (University of Hertfordshire): You literally can’t see them, and that’s what makes them extremely mysterious.
NARRATOR: They are bizarre quirks of nature…
REBECCA “BECKY” SMETHURST (University of Oxford): When we’re studying black holes, we’re right on the edge of human knowledge.
NARRATOR: …and yet, they are sculptors of the cosmos…
IMOGEN WHITTAM (University of Oxford): The jets from black holes are so powerful they can affect the whole shape and nature of a galaxy.
NARRATOR: …even shaping our own galaxy, the Milky Way.
DELILAH GATES (Princeton University): We had hints that black holes were at the center of all galaxies, like our own.
NARRATOR: Can we lift the veil…
HAKEEM OLUSEYI (George Mason University): Forget the one-way trip to Mars, I’m going in the black hole.
NARRATOR: …and reveal their secrets?
KIMBERLY ARCAND (Center for Astrophysics | Harvard & Smithsonian): Fermi revealed something completely astonishing and unexpected. We’ve never seen anything like it.
PRIYAMVADA NATARAJAN (Yale University): Finding these little pieces of the puzzle that did not fit is super exciting.
SHEPERD DOELEMAN (Center for Astrophysics | Harvard & Smithsonian): If you really want to understand the deepest questions of the universe, you have to understand black holes.
NARRATOR: Black Holes, right now, on NOVA.
As we gaze out at the Milky Way, our eyes are drawn to the light, hundreds of billions of stars serenely spinning through the cosmos.
IMOGEN WHITTAM: When we look up at the night sky, the stars and planets that we see are beautiful, but actually it’s in the space between these, in the dark patches, that some of the most fascinating things lie.
NARRATOR: In places where there is no light, objects of profound mystery bide their time. Awesome in their simplicity and perfection, we call them “black holes.”
KIRSTEN HALL (Center for Astrophysics | Harvard & Smithsonian): A black hole is an infinitely dense point in space, from which nothing can escape, not even light.
NIAL TANVIR (University of Leicester): It’s extraordinary to think that black holes are everywhere in the universe, that they have existed from very early times in the universe.
NARRATOR: When quiet, they are almost impossible to detect.
URMILA CHADAYAMMURI (Center for Astrophysics | Harvard & Smithsonian): We’re talking about a region of space where, if something falls, then we’ll never know about it, ever again.
NARRATOR: They hold the power to shred stars and worlds, but also, the potential to shape galaxies.
GRANT TREMBLAY (Center for Astrophysics | Harvard & Smithsonian): Black holes are one of the most fundamentally important singular objects that might dictate how galaxies form and evolve.
ANDREW PONTZEN (University College London): It’s natural to fear them, but we’re learning that they’re essential. You can’t live with them, but you also can’t live without them.
NARRATOR: And they may hold the secret to the ultimate fate of the universe.
KIRSTEN HALL: Black holes, on a fundamental level, challenge our understanding of physics, of the way that everything in the universe works.
SHEP DOELEMAN: Black holes are the most mysterious objects in the universe, full stop.
NARRATOR: To understand black holes, we have to start at the beginning, at the moment of birth.
CHIARA MINGARELLI (University of Connecticut and Flatiron Institute): Black holes that are a few times the mass of the sun probably formed from giant stars that were maybe about 20- to 30-times the mass of the sun.
NARRATOR: Enormous stars, burning bright blue with intense heat, but the brightest stars are the shortest lived.
GRANT TREMBLAY: A star is a big ball of gas, there’s outward gravity pushing in. The thing wants to collapse in on itself under its own self-gravity. But the fusion that’s happening within the star’s core liberates so much light that the outward radiation pressure prevents the collapse of that star. But eventually that gives up.
NARRATOR: A star like that can burn through its nuclear fuel in just a few million years. And when its power source runs out, it collapses under its own gravitational pull.
CHIARA MINGARELLI: There’s so much material that’s collapsing during their final few moments that they create this massive dense ball of neutrons that continues to collapse.
NARRATOR: A star 20-times the mass of our sun or larger, crushed by the force of gravity, until the star disappears, leaving only a ghost behind, a black hole.
This transformation does not await all stars. Smaller, less massive stars, like our sun, eventually become burnt out dwarves, when their fusion stops, slowly fading cinders.
But it’s possible that almost all the massive stars that dominated the early universe formed black holes when they died, because a black holes is simply what happens when enough matter is crushed into a small enough volume, dramatically warping the space around it.
DAVID ROSARIO: A river is a great analogy for the area right around a black hole. Here, I am far upstream, and the water is fairly placid. It’s not moving too fast. If I were to get into the water here and swim across, I’d be able to do that very easily. In the same way, if you’re far away from a black hole, you’d be able to get around with just a normal spacecraft, without too much trouble, and simple propulsion.
NARRATOR: But, the closer you get to the black hole, the stranger things become. The collapsed massive star crushes down so small and so dense, it ceases to have a physical surface at all, becoming an infinitely small point in space, exerting a profound effect on the space-time around it.
DAVID ROSARIO (Newcastle University): As the water gets closer to the waterfall, the speed of the water increases. If I were to jump into the water right here, the speed of the current would be so intense that I wouldn’t be able to swim against it, and I would be gradually pulled closer to the edge of the waterfall, until I reach a point of no return. And that’s the same around a black hole.
NARRATOR: Just outside the black hole, the fabric of space, itself, actually stretches inward towards the center.
DAVID ROSARIO: Not even stars, planets, people, even light cannot escape the pull of a black hole. It’s like a waterfall in the fabric of the universe.
NARRATOR: The black holes gravitational reach is not infinite.
URMILA CHADAYAMMURI: People have this idea that black holes suck, in the sense that they suck everything into them, but that’s not true. Black holes can only eat things that are within a certain distance away from them. If you’re further away, then the black hole has no way of eating you.
NARRATOR: But once in its grasp, you are lost forever. And this is the key to their mystery. The black hole’s interior is hidden from view, cut off from the rest of the universe by a boundary in space, the “event horizon.” Beyond this point, there is no escape. As we approach the event horizon, we get our first glimpse of the true weirdness of black holes.
DAVID ROSARIO: Ever since Einstein, we’ve viewed the fabric of the universe, not as something static, but instead something that’s fluid, something that bends and warps around objects with mass.
We call this space-time, a combination of space and time. See, Einstein’s insight was to realize that these two things are intimately connected, that when an object has mass, it not just bends space, but changes the passage of time, itself. In particular, the effect of a mass is to slow time down.
NARRATOR: In the region around the black hole, the warped space-time elongates light waves, distorting color.
DOUGLAS FINKBEINER (Center for Astrophysics | Harvard & Smithsonian): The event horizon is the place at which time stops when seen from far away. Someone who’s outside the black hole will see you get redder and redder, and your time will slow down, and you’ll kind of pass through the horizon, disappear forever.
NARRATOR: Black holes are like waterfalls in the fabric of the universe, where space contorts and time, itself, grinds to a halt, ensnaring light, making them lockboxes for the universe’s ultimate secrets.
STEPHEN HAWKING (Theoretical Physicist/Audio Clip): It is said that fact is sometimes stranger than fiction, and nowhere is that more true than in the case of black holes. Black holes are stranger than anything dreamed up by science fiction writers, but they are firmly matters of science fact.
NARRATOR: The vast majority of black holes are small, less than 20 miles across, and they usually wander alone through space. But if we turn our gaze towards the center of the Milky Way and journey inwards, through the gas and dust that shroud the galactic core, signs of something altogether different appear.
GRANT TREMBLAY: If you simply observe the stars in the very heart of our galaxy over about 20 years, you will observe them orbiting nothing. At the center of this swarm of stars is darkness. It’s a void.
NARRATOR: Scientists name this invisible enigma “Sagittarius A*,”although it is not a star at all.
ANDREW PONTZEN: Can you imagine how massive that object has to be to be able to pull entire stars into orbit?
NARRATOR: They believe it to be a black hole, more than 4,000,000 times the mass of our sun, many thousands of times more massive than any other in the Milky Way.
SUGATA KAVIRAJ: How did this monster come to live at the heart of the Milky Way?
NARRATOR: Sagittarius A* star is a supermassive giant, around which the entire galaxy spins, raising intriguing new questions about the role of black holes in our galaxy and the universe: How did it get there? How did it get so big? And what can it tell us about how black holes shape the cosmos?
BECKY SMETHURST: Would we even be here today without Sagittarius A*?
CHANDRA MISSION CONTROL: Just a few minutes away from the 26th flight of the shuttle Columbia with a crew of five.
KIM ARCAND: I think a night launch is particularly exciting.
CHANDRA MISSION CONTROL: We’re go for engine start. We have booster ignition and liftoff of Columbia.
CHANDRA MISSION CONTROL: Roger roll, Columbia, we’re looking in.
URMILA CHADAYAMMURI: Chandra is huge, about the size of a school bus. It’s the largest telescope to ever be launched by the space shuttle.
CHANDRA MISSION CONTROL: S.R.B. separation is confirmed.
KIM ARCAND: You’re stressed about the astronauts on board that are literally risking their lives to help us get a better view of the universe.
NARRATOR: In the summer of 1999, NASA’s flagship telescope for X-ray astronomy sets off from the Space Shuttle cargo bay.
GRANT TREMBLAY: Even two decades into its voyage of discovery, Chandra remains by far, the most powerful observatory that we have to observe the high energy universe.
NARRATOR: Almost 83,000 miles above the earth’s surface at its highest orbit, Chandra scans the sky with eight high-precision mirrors, engineered to detect X-rays emitted from extremely hot regions of the universe. For 14 years it searches among the exploding stars and clusters of galaxies, but then, on September 14th, 2013, Chandra chances on something else entirely.
IMOGEN WHITTAM: Chandra wasn’t looking for this at all, just happened to be looking nearby. So, it was a total surprise.
NARRATOR: As the telescope gazes into the constellation of Sagittarius, it aims to observe a large cloud of hot gas, but unexpectedly, it records a flash of X-rays just a few pixels across, coming from the seemingly empty space in the galactic core.
SUGATA KAVIRAJ: When we see something get very hot for a very short period of time, we get very excited. Something is causing it, something we can’t see.
NARRATOR: Some scientists believe the flash seen by Chandra is caused by an asteroid, ripped apart and burning up in a blaze hundreds of times brighter than the sun, releasing a burst of X-rays that Chandra can detect, almost 26,000 lightyears away.
JUDITH CROSTON (The Open University): If we see a level of X-rays being produced that’s so bright it can’t be explained by any other process, then we know that there must be a black hole there.
NARRATOR: It’s the behemoth at the center of our galaxy: “Sagittarius A*.
KIM ARCAND: You can take a telescope like Chandra and watch a black hole have a small snack, maybe like a human might have a little biscuit in the afternoon, and it’s something like an asteroid. And there will be a small sort of X-ray signature from that event.
SUGATA KAVIRAJ: So, it’s incredible that we can actually observe Sagittarius A*, which lies 26,000 lightyears away, actually eating something.
NARRATOR: But Chandra does not only look inwards, it also looks out, beyond the Milky Way. At the center of almost every large galaxy Chandra peers into, it finds evidence that our galaxy is hardly unusual.
REBECCA SMETHURST: We started to spot X-ray sources of light everywhere around the sky, and we started to realize something weird was going on in the centers of galaxies.
SHEP DOELEMAN: At the heart of most galaxies, we think now, there are supermassive black holes, black holes that weigh millions or billions of times what our sun does.
JUDITH CROSTON: It’s incredible that our modern X-ray telescopes, like Chandra, allow us to map out where these fascinating black holes are across the universe.
NARRATOR: Supermassive black holes seem to be an integral feature of the cosmos, but these supermassive objects raise questions: How do they form? And why are they so big?
BECKY SMETHURST: These things form over millions to billions of years. So, we can’t watch this happening. We can only see it at various different stages throughout the universe. And so we have to just piece it together, like a jigsaw puzzle.
NARRATOR: Some scientists theorize that the biggest and oldest black holes did not start life as stars at all.
PRIYA NATARAJAN: In the very early universe, we believe that you could have formed very massive black hole seeds by direct collapse of gas. So, these black holes are called “direct collapse” black holes.
NARRATOR: But the jury is still out.
KIRSTEN HALL: It’s possible that Sagittarius A* formed by direct collapse of material. What I think is more likely is that it formed by the death of a star.
NARRATOR: However Sagittarius A* was born, one thing is certain: it had to grow.
The newly formed Sagittarius A* begins to feast, gorging itself on, not just asteroids, but bigger game, like stars and massive clouds of gas.
IMOGEN WHITTAM: As it snacks on these nearby objects that wander into its path, it gets bigger and bigger and bigger.
NARRATOR: The black hole gains more mass and more gravitational power.
CHIARA MINGARELLI: But black holes that are a few times the mass of the sun can never grow to be a supermassive black hole just by eating gas and stars.
NARRATOR: How did Sagittarius A* speed up its growth? On September 14th, 2015, an international team of astronomers finds a clue, the aftershock of a truly titanic interaction: two colliding black holes.
GRANT TREMBLAY: The merger of two black holes, as you might imagine, is spectacularly energetic. It is so energetic that it causes ripples in the fabric of space-time itself, that propagate outward at the speed of light. And we have detected these ripples here on Earth with something we call “LIGO.”
KIRSTEN HALL: LIGO is an instrument that works by sending laser beams that bounce off of mirrors. When a gravitational wave passes by the earth, this changes the timing of the interaction of those laser beams.
DELILAH GATES: The stretching caused by a merger here on Earth is absolutely minuscule, but with advanced technology LIGO was able to do it.
NARRATOR: Many scientists now think that mergers like this are the key to how supermassive black holes like our own, grow so big. When another black hole wanders towards Sagittarius A*, they become locked in a gravitational embrace.
PRIYA NATARAJAN: First, it is sort of an intriguing dance. They kind of dance around each other, lose energy, and slowly spiral into each other.
CHIARA MINGARELLI: This dance gets faster and faster and faster and faster, until they finally merge.
NARRATOR: Sagittarius A* cannibalizes its cousin, creating ripples in the fabric of the universe itself.
IMOGEN WHITTAM: These mergers were fundamental to making Sagittarius A*, the monster that we see today. They happened billions of years ago, right at the beginning of Sagittarius A*’s life.
NARRATOR: More meals follow, stars, gas clouds, whatever strays too close. And as our black hole’s mass and influence grows, its surroundings are changing, too.
The sea of stars and gas around the black hole continues to grow, gradually evolving into the familiar spiral disk we call home: the majestic Milky Way, with the supermassive Sagittarius A* at its core.
SUGATA KAVIRAJ: So, when Sagittarius A* becomes a supermassive black hole, it really comes of age, and it acquires the ability to have a transformational impact on the evolution of the entire galaxy.
SHEP DOELEMAN: Black holes are the ultimate engines in the universe. When you think about a car, the first thing you’re interested in is, “How does it work?” You open the hood and you look at the engine of the car. With a black hole you’re asking, “I want to lift the hood up on an entire galaxy. How does a galaxy power itself, at its very heart?”
NARRATOR: The center of the young galaxy is rich with swirling gas and dust, more offerings to feast on.
This is a gluttonous period, a new era for Sagittarius A*, when the invisible giant has the power to sculpt the galaxy.
IMOGEN WHITTAM: As Sagittarius A* is gorging on food, the food that it’s waiting to eat is swirling around the central supermassive black hole, in this violent, energetic disk. And the matter is ripped apart by the gravity, which causes the protons and electrons to then make these twisted magnetic field lines.
HAKEEM OLUSEYI: Everything is rotating and orbiting, so at the center of this black hole, this accretion disk, you have a twisted magnetic field, almost like a tornado.
KIM ARCAND: Right before the material approaches that event horizon, that eternal prison, if you will, it can be redirected instead.
NARRATOR: And from the blazing tumult, the super-heated material is thrown out along the magnetic poles, two high-powered jets, launched out into the cosmos.
SHEP DOELEMAN: They can reach hundreds of thousands of lightyears from the black hole itself.
NARRATOR: It’s only recently that we’ve begun to grasp the huge influence of Sagittarius A* on our galaxy and the role that those super-powered jets may have played.
Just over a decade ago, astronomers made a completely unexpected discovery.
BECKY SMETHURST: It was this whole piece of our galaxy that we never knew was there before. It would be like finding a brand new continent on Earth.
NARRATOR: The Fermi Space Telescope was built to detect gamma-rays, the most energetic radiation in the universe.
DOUG FINKBEINER: Fermi is roughly a hundred times as sensitive as previous gamma-ray telescopes, so it has the sensitivity to see things that we just simply couldn’t see before.
NARRATOR: Orbiting the earth once every 96 minutes, Fermi constructs a map of the cosmos and uncovers an invisible landscape, the most energetic regions of the galaxy, highlighted across the sky.
KIM ARCAND: So, we pointed the Fermi telescope towards our very own supermassive black hole, and we had a picture of what that area sort of looked like, in our minds, at least. But then Fermi revealed something completely astonishing and unexpected.
NARRATOR: Emerging from the plane of the Milky Way are two enormous bubbles, each one stretching 25,000 lightyears, together reaching half the width of the galaxy.
DOUG FINKBEINER: If you could see in gamma-rays, the Fermi bubbles would be about the biggest thing you see on the sky.
DAVID KAISER (Massachusetts Institute of Technology): They look like huge dumbbells going straight up and straight back from the center of the black hole.
NARRATOR: The bubbles match the imprint scientists expect an enormous eruption from Sagittarius A* to leave on the galaxy.
JUDITH CROSTON: We had had some clues that the Milky Way might have had a more energetic and active past, but the incredible thing about the Fermi bubbles was that they suddenly gave us concrete evidence that the Milky Way was much more energetic, at some time in its history.
NARRATOR: When our black hole gorges, it unleashes a towering inferno of superheated matter.
GRANT TREMBLAY: A supermassive black hole can impart something like a trillion- trillion-atomic-bombs-per-second’s worth of energy.
SHEP DOELEMAN: If we were to be in the line of fire of one of those jets, it would be catastrophic for us. We’d be vaporized.
NARRATOR: Every planet in the jet’s path could have its atmosphere stripped away.
But further out in the galaxy, these violent outbursts from Sagittarius A* may have played a surprising role, because the hot gas displaced by a supermassive black hole has a calming effect on the galaxy that hosts it.
KIRSTEN HALL: In order for stars to form, you need very cold and very dense gas, because stars form through the collapse of material.
URMILA CHADAYAMMURI: So, instead, if you have something like a supermassive black hole that is sending out these hot jets into the galaxy around it, those jets are going to heat up the gas. Now, the gas is no longer cold enough to collapse and then form a star.
SHEP DOELEMAN: There’s a symbiotic relationship between the supermassive black hole at the center and its host galaxy. And this relationship determines the rate at which stars form, planets form, and ultimately, in some sense, why we are here.
NARRATOR: After spending billions of years consuming the gas, dust and stars around it, there is little left to feast on. Our black hole falls dormant.
Today, the Milky Way has entered an era of calm, and Sagittarius A* is a sleeping giant, the enormous bubbles spotted by the Fermi telescope, echoes of a lively past.
DOUG FINKBEINER: You never want to assume that you live at a special time in the history of the universe, but it is kind of a special time, in that, right now, the black hole is very quiet, and it must have been much more active a few million years ago.
NARRATOR: As our understanding has grown, our picture of black holes has transformed: no longer sinister monsters, but agents of change and creation, sculptors of the cosmos.
DAVID ROSARIO: We are far from unlocking all the secrets of our galaxy’s supermassive black hole. And, in fact, the stuff that remains is probably the most interesting: what happens inside a supermassive black hole and at its event horizon.
STEPHEN HAWKING (Audio Clip): Black holes challenge the most basic principle about the predictability of the universe and the certainty of history. Nothing could get out of a black hole, or so it was thought.
NARRATOR: Black holes are where two of our greatest theories collide and clash.
SHEP DOELEMAN: So, you’ve got these two primal forces in the universe: gravity, which we all understand and feel with our bones, and then you’ve got quantum mechanics, which governs the theory of the ultrasmall, how atoms and nuclei come together. The black hole is where gravity and quantum mechanics finally meet.
JIM GATES: When we try to take the mathematics of the very large and try to combine that with the mathematics of the very small, instead of matching, they get into a fight. And so, we don’t have a consistent way to describe both.
NARRATOR: We can begin to probe this deep mystery by investigating the heart of Sagittarius A*. Scientists have studied dozens of stars in its orbit, some passing just a few billion miles from the event horizon, a hair’s width on galactic scales. And these flybys could have catastrophic consequences, because some of these stars likely have planets in orbit, planets that may stray too close: moths to a flame, pulled from their parent stars towards the abyss.
GRANT TREMBLAY: So, imagine you’re some alien civilization, looking up at your lovely home star, S2, in the sky. And one day, the thing starts wandering closer and closer to what we call the “tidal disruption radius” of Sagittarius A*, this four-million-solar-mass black hole.
IMOGEN WHITTAM: If you fell into a black hole, you’d pass the event horizon and actually, bizarrely, you’d see nothing. There’s no physical barrier. There’s no big line in space saying, “point of no return.” You would just drift, very casually, gently across the event horizon.
NARRATOR: If we could stand on such a planet and look outwards, we’d see something spectacular.
HAKEEM OLUSEYI: You’d see a distorted universe. And, in fact, you see it distorted in both time and space.
IMOGEN WHITTAM: You’d see it playing out at an amazingly fast speed. The rest of time would play out unbelievably fast in front of your eyes.
NARRATOR: But eventually, tidal and gravitational forces become too strong, stretching space and everything in it.
IMOGEN WHITTAM: Your feet would be pulled more strongly by gravity than your head, so you’d be stretched out into a giant string. And eventually, you’d be one long string, one atom thick. We call this “spaghettification.”
NARRATOR: Boulders become rocks, rocks become sand, whose very atoms are then pulled apart. Gravity and the quantum world collide. Ahead: the heart of the black hole, the singularity, where all journeys in terminate.
HAKEEM OLUSEYI: Our idea of a singularity is that everything is compressed beyond what it can be, until it’s nothing but yet still exists. That is…wow.
NARRATOR: Over trillions of years, all the stars around Sagittarius A* will gradually fade out of existence…
SUGATA KAVIRAJ: Long after the last ever sun sets on any planet, black holes will continue to roam the universe.
NARRATOR: …the final dark age.
GRANT TREMBLAY: If nothing can ever escape, if this is some eternal prison, is that the end of the story?
NARRATOR: Perhaps not, because scientists now believe that even Sagittarius A* will die. And its death will come at the hands of what might seem an inconsequential effect, first described almost five decades ago.
CHRIS DONE (Durham University): So, in 1975, Stephen Hawking published this amazing paper, showing that black holes aren’t absolutely, completely black. They glow very, very faintly. They have a temperature associated with them. And you can write that temperature very simply in an equation that’s just beautiful.
It links together so many different parts of physics. It’s got gravity in it. It’s got the mass of the black hole in it. It’s got the speed of light. It’s got constants relating to atomic physics, the micro world. And it’s putting all of these together and giving us a temperature.
NARRATOR: Hawking’s equation has huge implications for the future of the black hole.
CHRIS DONE: So, if something has a temperature, it’s glowing, it’s radiating. Like, when you put your hand close to a fire, you can feel it. And that losing energy, for a black hole like Sagittarius A*, over timescales that are hugely long, it’s going to evaporate away. It’s going to disappear.
NARRATOR: Very gradually, this Hawking radiation will erode away Sagittarius A*, until, many trillions and trillions of years into the future, in a final burst of light, our black hole will disappear. And then the Milky Way will be completely dark, for all eternity.
CHRIS DONE: So, why does it matter if these black holes disintegrate in the far distant future? Well, the discovery of “Hawking radiation” raised some profound questions in physics.
If I was to set fire to this piece of paper with Stephen Hawking’s equation written on it, what happens to all that information as it burns away, as it radiates away? Do we lose it from the universe forever?
Maybe, if I could sweep up all the ash, if I could find all the photons and reconstruct them, maybe I could reconstruct that piece of paper, even the equation written on it.
So, does this also apply to black holes? What happened to all the information contained on all the material that ever fell into a black hole? And as a black hole evaporates, what happens to it?
STEPHEN HAWKING (Audio Clip): Black holes ain’t as black as they are painted. They are not the eternal prisons they were once thought. So, if you feel you are in a black hole, don’t give up. There’s a way out.
NARRATOR: If information somehow escapes from Sagittarius A*, as it evaporates away, the implication is profound.
Scientists now believe that every star, asteroid, planet, everything that ever fell into Sagittarius A*, may live on; every aspect and position of every particle, encoded as information, all that you would, theoretically, need to put the whole back together.
REBECCA SMETHURST: So, the memory of every single thing that’s fallen into, become part of, Sagittarius A* in the Milky Way, hasn’t been lost. It’s still there. It’s just that we can’t access that now. But maybe we might be able to read the ashes of that memory in the far future of the universe.
NARRATOR: But how can anything escape a black hole’s grip?
ANDREW PONTZEN: The defining fact of a black hole is that nothing should be able to get out. And yet, when you look at Hawking radiation, it seems to be suggesting that quantum physics does connect up the inside back to the outside. We just don’t really know how.
NARRATOR: Black holes force us to consider nature in entirely new and mind-bending ways.
DELILAH GATES: People aren’t at all certain about the resolution to what happens when we throw things into black holes. As far as where the information goes, it’s still an open question.
DAVID KAISER: Maybe it gets sent to a portal to another dimension, maybe it gets pumped into some other branch of a larger multiverse.
NIAL TANVIR: Some people imagine that black holes are really just a kind of quantum fuzz, a fuzzball.
SHEP DOELMAN: Some people think that all the information that fell into the black hole is somehow encoded on its surface in a hologram.
RICHARD ANANTUA (Center for Astrophysics | Harvard & Smithsonian): But we’re not really privy to any of this information. And if we want to find out, we’d have to go in.
NARRATOR: Whatever the solution proves to be, it will have ramifications far beyond the black hole itself.
CHIARA MINGARELLI: This theory of quantum gravity that’s so elusive right now, that is what we would need to describe what’s happening inside black holes, could either be the most exciting development to happen in the next decade or maybe even the next century, or it could be an alarm bell, going off in our heads, that maybe Einstein’s theory of gravity is not the final word on gravity.
NARRATOR: Solving the mystery of black holes may be our best chance to complete the picture of nature that has eluded us for the last century.
SUGATA KAVIRAJ: So, perhaps the important thing isn’t what the answer turns out to be. The important thing is that we will gain a fuller understanding of the cosmos by studying these remarkable objects.
HAKEEM OLUSEYI: Studying the universe has completely changed our universe. We have to rethink everything over and over again, like, it’s almost like, “tear up the universe we know and write a new one.”
NARRATOR: We’re still a long way from fully comprehending the secrets of black holes, but we’re beginning to lift the veil. Far from being a mere cosmic aberration, black holes fundamentally shape our universe.
SUGATA KAVIRAJ: So, it’s extraordinary to think that we might be fundamentally connected to something that we didn’t know existed for the vast span of human history.
HAKEEM OLUSEYI: The beautiful thing about black holes is that they’re such a rich source of information. We’ve learned so much about the universe from studying black holes: space, time, the very fundamental nature of reality.
NARRATOR: Bit by bit revealing the deepest mysteries of the cosmos.
ANDREW PONTZEN: We’re in a golden age of discovery about black holes. We understand how they merge; we’ve discovered their colossal jets, and we’re beginning to see them, not just as destroyers, but also as creators and sculptors. And all that is just the beginning.
REBECCA SMETHURST: Our story’s happening now, but black holes, they are going to outlive us by trillions of years. Their story is just getting started.
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Here's a link if you want to watch and harvest the transcript.
NOVA Universe Revealed: Big Bang
https://www.pbs.org/wgbh/nova/video/nov ... -big-bang/
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