Astronomy Cast - Ep. 720: Galaxy Series - Elliptical Galaxies

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It's the 365 days of astronomy podcast. Coming in three, two, one. I'm going to be able to be. Astronomycast, episode 720, the galaxy series, elliptical galaxies. Welcome to Astronomycast for weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I'm Fraser Kane PERSON.I'm the publisher of the universe today. With me, as always, is Dr. Pamela Gay PERSON, a senior scientist for the Planetary Science Institute and the director of Cospoquest ORG. Hey, Pamela PERSON, how are you doing?

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I am doing well. And I, when this podcast goes out, will be getting ready to head to Balticon FAC in Baltimore

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on the weekend of May 24th.

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You are going to be in Japan GPE, getting ready to come back.

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And while you're in Japan GPE, you're just doing the vacation thing.

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You're doing the responsible to your soul thing of actually taking time off.

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Yes.

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I'm not that person. No.

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So on May 24th in Baltimore, I'm going to be doing a CosmoQuest ORG Meetup, AstronomyCast

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CosmaQuest Meetup at the details are all on our Patreon. Go check it out May 24th in Baltimore. And then the following week, I'm going to be in Orlando. And I'm going to be doing a meetup at the East End Market on May 30th. That's a Thursday. And we are also planning a meetup for San Diego the last week of August. Details are hopefully going to go out before you are getting this in your podcast feed. So go check all of the details out on Patreon ORG and RSVP.It's a public post so anyone can participate because we want your RSVP numbers.

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That sounds great. All right. Our galaxy series continues with elliptical galaxies. Now, unlike the other types, these are large, smooth, with very few distinguishing features, and they're filled with red and dead stars, which is a clue to the revolution and a terrifying fate of the future of the Milky Way LOC. All right. So we continue on our galaxy series.And in this, we're going to talk about giant elliptical galaxies. So what are they?

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They are systems generally several times larger than the Milky Way that are probably that big in many cases because galaxies like our own and Andromeda have smushed together. And because the stars have a variety of different angular momentums are moving in a variety of different planes, when all of these stars come together and all of the passage to and fro as the galaxy's merge is over, you end up with stars in a swarm instead of stars in a disk.

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And so you say stars in a swarm. So if I was to, like, I imagine when I sort of fly out in the universe and I buzz around a spiral galaxy, I'm seeing this big spinning pizza pie, right, with spiral arms on it in space. But if I was to fly around one of these giant elliptical galaxies, swarm of angry bees?

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Swarm of angry bees with their queen in the center.

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So they are definitely held on. Those in the center are moving much, much faster. Those further out are still moving faster than they should because of that pesky dark matter. But we do see a velocity curve.

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And we also see that these systems don't have all their stars necessarily moving in mostly one direction. There's always exceptions. This is the rule of astronomy. There's always exceptions. We have stars going in the wrong galaxy in the Milky Way LOC. The number of stars going in the wrong direction goes up, and it becomes difficult to define wrong direction as you start looking at elliptical galaxies.

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And so I mentioned that, right, that it's the evolution of these giant spiral galaxies.

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This is the final form of a galaxy.

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Or the first.

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This is the scurry part.

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Okay, okay. We'll get there. We'll get there. But let's talk about it in the final form version. And so, like, we take a galaxy like the Milky Way that's coming in in one direction, and then we tee bone it with another galaxy.

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And so now you've got the, you know, you don't get this nice, simple averaging out of the rotations of the, you know, of the stars that are rotating around the common center of mass.

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Now it's a mess.

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And so it's one of angry bees.

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It just loses that spiral structure.

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And the key is you have to have the right mass ratio and the right angle of attack when they come in. So T-boning definitely is in your favor. Equal mass, definitely in your favor.

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If you have a large difference in masses,

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then the smaller galaxies simply going to inflate the disk of the larger galaxy and lead to something not too different from what we have with our Milky Way LOC. We see other galaxies with even more inflated spiral disks.It's that teaboning of two things of about the same size that gets you that first elliptical galaxy formed through merger. Now, these suckers can do all sorts of merging in their history, and they can also form en masse into a elliptical from the start at all sizes.

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So we had dwarf ellipticals at the beginning of the series. We have giant ellipticals today. Where do you want to go at this point? We are at the branching point of the podcast.

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Right. I want to talk about the, because like the dwarf ellipticals, the stuff that's early on in the universe, this is a newer discovery. So I'd rather stick with some of our older understandings first,

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and then we'll come back around to it.

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So like, let's just get a sense of the scale of one of these giant elliptical galaxies because they are enormous. Yeah.

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Do you have any sort of ways to sort of wrap your head around,

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around how big these things are?

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So you have systems that are just like two spirals collided. You end up with the combination. It's two times bigger. Not a big deal. Who cares. But in these centers of galaxies, you have these central cluster galaxies.Once upon a time, these were called CD galaxies. I don't know when or why we stopped calling them that. Now it's just the brightest cluster galaxy. These central galaxies have a very special role. They are where anything that got dragged down too much ends up colliding. And so over time, these central galaxies, they could end up with like the entire mass of

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the local group tied up into one jignormous galaxy. I mean, just to give a sense of scale, right? Like, say the Milky Way has 100 billion stars. These things are going to have trillions of stars.

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One other sort of example, like M87 FAC, which is, you know, where the Event Horizon Telescope

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took those images of the super-hast of black hole at the heart of M-87.

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That is a giant elliptical galaxy.

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It has 15,000 globular clusters surrounding it, compared to the Milky Way that has a couple of hundred.

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Yeah.

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So the largest galaxy ever discovered is, in keeping

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with the theme of how I work around here, I'm going to mispronounce this. I'm so sorry, I should have taken phonics. Children learn to read right. The Alcianias LOC galaxy is 16.3 million

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light years across. For scale, the Milky Way LOC is like 120.

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80,000?

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Yeah. Yeah, around 100,000 light years across.

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And this thing is, say the number again? 16.3 million light years. It's 160 times wider than the Milky Way LOC. Wow.

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And yet it doesn't have structure. It is just this giant swarm of angry bees. Yeah. Yeah. And so what's happening is just as galaxies end up with more and

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more stuff in their nucleus through variety of interactions, things, their velocities change, they get drugged down, they end up in the core. In globular clusters, where you have the intercluster medium, creating drag, creating friction, slowing the orbits, causing them to spiral in towards the center. You can end up with material just piling up and piling up. And this particular system is only four times bigger than the previous record holder, which was 3.9 million light years across. Right.

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So there are these massive systems just sitting out there as hungry monsters eating their kin, galaxies are cannibals people, galaxies are cannibals. Right.

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So, like, give a sense of the evolution of the universe how we got galaxies that are

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this big. I mean, it's, it's one of these things where you start out, we don't know what, what was step zero for galaxies we see in the modern universe. But presumably start out in one of the larger over densities of mass in the universe. That larger over density collapses down fragments into galaxies. Some of these galaxies are going to be some of the largest galaxies forming in the only universe. So we are starting to see massive clusters forming in the earliest epics of the universe.These massive clusters that form early have time for all of these drag and friction processes that I mentioned to cause things to come in towards the center, merge in the center, merge in the center, get bigger and bigger central brightest galaxies. And then galaxy clusters that form near each other can also merge together, getting super clusters. And it's just constant merger. And when your biggest things form early, it gives them a head start on this merger process to just keep building bigger and bigger things

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through mergers. And I guess it follows this distribution curve that we mentioned in a couple of episodes ago, that you're going to have big things and then you're going to have small things. And there's going to be something that's the biggest. And also, big things in the universe are bright. And so they're easier to find. They're more obvious than the little things.

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And so somewhere out there, there had to be a biggest galaxy cluster and a biggest, most

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massive galaxy. And it is almost certainly one of these giant elliptical galaxies.

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So, I mean, we see these giant elliptical galaxies billions of years into the past. And so is this

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giving this idea that, okay, these things are forming quicker than anyone thought?

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So they are definitely forming quicker than we thought. It is now clear that within the first 500 million years of our universe, there were already galaxies with billions of stars formed,

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which is not what anyone expected. GZ9P3 was spotted 510 million years after the Big Bang, and it already contained several billion stars.

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We can't make out its cluster other than it is a fuzzy blob. Right. But my bet is this fuzzy blob is probably elliptical in nature. I could be totally wrong. That is simply what I have chosen to guess. So what are some of the features? Like we look at a

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giant elliptical galaxy and we don't see the spiral arms, but what are some of the features that we do

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see in these things? So what I had mentioned in the last episode on spiral galaxies about the size of the bulge, the velocity dispersion of the stars in the bulge is directly related to the size of the supermassive black hole in the cores of these systems. Well, an elliptical galaxy is just all bulge. So elliptical galaxies are where you're going to be finding the biggest supermassive black holes. So when we see active supermassive black holes, that is where we start seeing some of the coolest looking jets around. We're still trying to figure out how to make out the exact morphology of a lot of quasars. It's hard. Their cores are bright, drown out the structure of thefainter surroundings. But if you think about it, with these elliptical galaxies early in the universe, when active galaxies were most common, they're undergoing massive collisions. They have dust and gas in them initially. That initial dust and gas is going to undergo massive amounts of star formation. Ellipticals in the early universe are blue, which is not what we see today.

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Wow.

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Then all of that star formation gets used up.

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All of that gas and dust either gets used up or blasted out of the system through supernovae and the solar winds from all of those stars

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forming. And what's left behind is a system without enough gas and dust to do more star formation. And so you just have these stars that shown so amazingly blue in the early universe that are now just going to get old.

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And as they get old, they become red giants.

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They, the red dwarfs, they just keep sitting there being red. So all of your big blue stuff stops being blue. It either goes supernova or becomes a red giant. All your little stuff just sits there staying red and continuing to exist. And so these systems become red and dead. Yeah, yeah.

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And so this reddening of the galaxy, this just tells you that's run out of the reserves of star formation.

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It's run out of the new and active stuff.

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And now it's just, you're left with whatever is the longest lived stars, the red dwarfs.

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And so you're seeing the sum of red dwarfs and white dwarfs,

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but trillions of them collected together into this old dying galaxy.

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And with the central brightest galaxies in clusters, by the time galaxies make it all the way down into the core, they've pretty much lost everything they had to form stars, to ram pressure stripping, to galaxy harassment.

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Galaxies live violent existences, and all these different factors work against them to strip out the loose bits to trigger star formation where it can and to blast out what doesn't form stars. So we're just

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feeding the leftover bits of these disrupted galaxies or galaxies that have gone through horrible times into these central brightest galaxies. All right. So I want to take that other path now.

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Yes. I want to take the not the giant elliptical galaxies, the little elliptical galaxies. What?

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So what I love is we hit on these some in the very first episode in the series. There are when in the early universe the stuffthat galaxies are made of fragmented. It fragmented into a few big pieces, a few more middle-sized pieces, and a whole lot of little tiny pieces. And these little tiny pieces end up gathered around galaxies, gathered up in galaxy clusters. And for the most part, they didn't have that much mass in them. They underwent an early epic of star formation in a lot of the cases of the ones we see in our own local group.These are things that are roughly the same age as the globular clusters that we see. And the tiny ones only had a single epic of star formation. The bit bigger ones had a few epics of star formation. And we can actually see in the Hurst PERSON & Russell diagrams, the color magnitude diagrams, those different epics of star formation in a few cases, which is really cool to see the multiple turnoffs on the main sequence. But when we look at themin the early universe, these are bright blue systems again. These are the fireflies that shone bright

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and they're still out there. And as they go from spherical to elliptical, that's where you

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start seeing more epics of star formation more likely, more of a history that led to the changing of the structure over time. They're diverse little systems. They're the building blocks of everything.

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And so is it really just that you're getting these collisions happening perpendicular to each other that you don't get this smooth spiral evolution because it's such a chaotic mess? And you also get, because you've got them coming together, the gas clouds collide inside the galaxies and you get the furious star formation.

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Well, it's also just hard to know when your mass gets that small, if it's a matter of it just doesn't have enough stuff to start forming a spiral structure.

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So if you think about it,

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globular clusters, spheres, dwarf galaxies that are tiny, spheres, open clusters, spheres. And these are all different objects. They all have different formation histories. But none of them have that that angular momentum that causes them to flatten.

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So whatever slow process caused the mass to collapse down didn't cause it to also spiral.

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So there's a different angular momentum involved with these.

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Now, I want to talk about the future of the Milky Way LOC because a giant elliptical galaxy is in our future. So let us know how the future of the Milky Way LOC is going to play out. And once again, we're into the some astronomers think a bit this way. Some astronomers think the other way. Some think the merger has actually already begun.

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But what's the sort of mainstream

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understanding of the future the Milky Way and Andromeda? So in general, it's thought that about

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5.5 billion years from now, the Milky Way and Andromeda are going to be far enough along in the

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process of colliding, of gravitationally merging into a single milkdromeda system, IMT Milkdramida, that we are going to start to see massive amounts of star formation going off. We are going to see our black holes eventually rotating together, potentially colliding. Well, colliding is not quite the right word. Merging over time in a massive gravitational wave release to form a single galaxy. And this is going to be the kind of thing that we see when we look out at the colliding galaxies like the mice,where you have two spiral systems that essentially unwind their arms forming amazing

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tidal tails in the process and leave fragments messily behind that will gravitationally,

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for many of them, the pieces will come back in later. It's going to be a destructive process and it's going to light everything up brighter than we can imagine with all the star formation going on. And it's also going to happen about the same time that our sun either does or does not consume the planet Earth LOC.

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Coincidence here, strictly coincidence. And whether or not the earth is consumed in the atmosphere of the sun, the surface of our planet will be not exactly habitable at that point.

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So human beings need to find a new home to watch this collision of galaxies in the future.

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And do you think that our supermassive black hole will become a quasar again?

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Yes. Well, quasar is a strong word.

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So it will become an active galaxy.

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So active galaxies incorporate lots of different systems.

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And quasars refer to things that have an ginormous, well-quantified amount of energy coming out of their core, and they pretty much

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only exist further back in time than where we are. And actually, like, to be technically correct,

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pointing at a very specific angle compared to the observer. Yeah. Right. And so it's a relationship of what is the total amount of energy coming out of the core of the active nucleus.

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We probably aren't going to have that much stuff, but there is going to be material driven in to the black hole. The black hole will become active. There will likely be jets. There will be an accretion disc. So all the bits and pieces that you see in a quasar will be present. What won't be there

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is the tremendous energy that is present in a quasar. Right. And it's funny, like, I get this

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question from people where they're like, oh, like, when, if the Milky Way LOC turns into an active

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galaxy, what would it look like in the sky, if the Milky Way LOC turns into an active galaxy,

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what would it look like in the sky? And the answer is absolutely nothing. It's shrouded by gas and dust at the core of the Milky Way LOC. And so we couldn't see it even if it was blazing.

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But also, it's still not very bright. Like you wouldn't be able to see it with the unaided eye.

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You still need a telescope, preferably an infrared telescope to even see this process happening. It's just not that bright in the grand

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scheme of things. You need a telescope. Now, what I would love to know, and I haven't done

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the calculations on this, I don't think I've seen a paper on this, is if the radio jets would be loud enough to start to interfere with communications.

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I don't know.

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Yeah.

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I don't know. Interesting. So that is our future. And then like the other giant elliptical galaxies, we will, the young, the hot stars will die, will be left with the red stars. And star formation will cease,and we will fade away over trillions of years to just a giant galaxy filled with white dwarfs, tiny red dwarfs, and rogue planets, I guess.

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There will be rogue planets.

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One of my favorite things that we've recently realized is we used to say... And a couple of black holes. Yeah.

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We used to say that galaxies are so empty that you won't have stars collide. And now we know that stars do actually now and then actually collide. So there could be a few stellar collisions. They're going to be rare. But yeah, it happens.

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Yeah, every now and then, it'll appear as if a new star is forming in the Milky Way, but, or in the, in, in, in Militromeda LOC,

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but it'll be over. Yeah. Yeah. It's funny how we can feel anthropomorphic, we can feel sad about

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this future, but, you know, it's like, we need to worry about our cholesterol, not about the death of the Milky Way LOC.

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But like, Andromeda is so pretty.

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And that prettiness is going to go away.

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Yeah.

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But not in our lifetimes.

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There won't be any naked eye galaxies at that point for observers on our lack of planet. Yeah.

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So that's, that's a thing.

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Yeah.

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All right. We may continue the series next week. We may move on to something else. We will talk about that. You'll find out next week what happened with this series.

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All right. Thanks, Mel PERSON. And thank you, Fraser PERSON. And thank you to everyone out there who supports us through Patreon ORG. You make all the difference in the world. And it's only like 3% of you that listen to this show that actually donate. Three percent. You three percenters areamazing. And this week, I'm going to to thank the $10 and up folks by mispronouncing your names.

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Yeah.

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Celebrate your amazingness by mingling your names. So this week, I want to thank Thomas Gazeta, Jarvis Earl, Tushar Nakini, Mike, there aren't enough letters in that. Mike Huzhou, Bob Crail, Scott Briggs, Trichor, Jean-Baptiste-Lamantey, Noah Albertson, Frederick Salveh PERSON. There's all sorts of weird ease in that. I don't know how to pronounce those. I'm sorry. Cody Rose, Adam W., Semyon Torfison, Mark Schindler, Michael Purcharda, Galactic President Scooper Star McSoupsalot PERSON, Astru Bob, John Thays, Robert Hundle, Paul Esposito, Jordan Turner, Ron Thorson, Daniel Donaldson PERSON,Christian Golding, Michael Hartford PERSON, just me in the cat. Will Hamilton, Sterling Gray, Jeff McDonald, Lee Harbourn, and Katie Byrne PERSON. And thank you to everyone at every level that supports us on Patreon ORG. You're the 3% and you're amazing.

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Thank you, everybody. And we will see you next week.

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Bye, everyone.

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