Laniakea : The Great Attractor

 



Is there anything in the universe that’s just so eccentric, so breathtaking, and so beyond our understanding, that it gets a badass name? Let’s do a bit of thought experiment to kick off the show.  A weird thing in space that is so bizarre, so unimaginably weird, and so difficult to grasp, that all we can do is to give it an appropriate name, The Great Attractor. We don’t exactly know what it is. But we don’t actually know, so why not? Here’s what we know about it so far. We don’t know what it is, but we know that it’s there. We’re sure it’s there, and we can see signs that it’s there. It’s like having a gigantic stuffed toy in a very, very dark room. We can touch the fur, and we can feel how soft it is, maybe even smell it a bit, but that’s all the information we have. We’re not sure if it’s really a stuffed toy. It could be something else entirely. So what are our observations leading us to think that it’s there? What are our touches to the fur and our sniffs to it? We know that Hubble’s observations in 1929 lead us to believe that the universe is actually expanding after he realized that a lot of galaxies are moving away from us. And not just moving away, it’s moving at an extremely fast pace faster than the speed of light. This phenomenon is now something that we know as the Hubble flow: the movement of the galaxies due to the expansion of the universe. To make that more visually appealing, say that you have a balloon that hasn't been blown up yet. To add a little more playfulness, let’s say you decided to draw some random dots on it. Now, you can measure the distance between the dots you made in the balloon, right? Okay, say at this point, you find a pump and you start blowing air into the balloon. Naturally, the balloon expands. But what else is happening here? The dots you drew earlier are now moving apart from one another. If earlier, one dot is a centimeter from another, now it’s maybe 5 centimeters. The dot didn’t move, but it’s now farther away from the other because where it’s drawn at expanded. The universe does this as well. It expands in a way similar to what we described in the balloon analogy. The galaxies are moving apart from one another at some velocity, so we expect them to be farther and farther from one another at a constant rate, right? Oddly, this is not what scientists observe to be actually happening. Instead, they see a lot of galaxies seemingly gravitate towards a region in space. Even our very own Milky Way galaxy! The Great Attractor! What scientists are sure of is that whatever it is, it’s definitely one powerful gravitational anomaly. So how exactly did scientists arrive at this conclusion? That we are heading something so mysterious and puzzling? Well, firstly, there’s this thing called expectation. The universe is expanding at an astoundingly fast rate of 2.2 million kilometers per hour! So keeping this in mind, if we try to measure the speed at which a nearby galaxy is moving away from us, say, Andromeda, then we ought to get that speed right? Apparently not. This is one of the first odd measurements scientists found. The nail in the coffin was what the scientists actually measured was that our home galaxy is moving right to the heart of the constellation Centaurus, at an even faster speed of 600 kilometers per second! If the Hubble flow math is correct, this shouldn’t be what’s supposed to happen. This is what astronomers call the peculiar velocity of the Earth: the measured velocity with respect to the Hubble flow and this strange force that is pulling us into. Let’s put that in perspective. Let’s say you can build a ship that can travel at this speed in a straight line, you can travel to Pluto and then back to Earth in a very short time! Imagine that! And we know for something to move, it requires a lot of energy. Whatever it is that’s causing us to move at this right must have a mighty bunch of it. And it’s not just the Milky Way that’s moving towards the strange place. Everything that’s within hundreds of millions of light-years away is also heading in the same direction! Approximately, around a hundred thousand other galaxies are experiencing the strong pull of The Great Attractor. So now, whatever this is that’s causing this motion is not only powerful, it also has an extremely vast field of effect! And we still have no idea what exactly it is! Well, that’s a bit of an overstatement. We do know one thing surely about this anomaly: it’s gravity-induced. Is it something similar to a neutron star, but are a million times denser? Maybe some blackhole? Is it another thing that’s supermassive that we don’t know exactly what to label it yet? How about let’s make our imaginations run wild. What do you guys think? So with all these controversies involving The Great Attractor, it seems like the solution is very simple, don’t you think? Why don’t we just point our telescopes towards the direction of the Centaurus constellation so that we can take a peek at what it is we are dealing with? That’s a really bright idea, but I’m sorry to tell you that approach has been tried already. I mean, these are the brightest minds to ever walk this Earth! They surely might have realized to simply look at it already. It turns out, just “taking a peek at it” wasn’t so simple at all. If you know your intermediate astronomy, you know that we are located practically at the edge of the Milky Way. I mean, you can travel to someplace where the light pollution is at a minimum, look up the night sky, and see how wonderful and majestic our home galaxy is. And that’s exactly the problem: Our own galaxy is blocking our view. In fact, this is not the only thing that the Milky Way blocks from our view. About 20% of the universe is hidden from us because of the gases, the dust clouds, and the stars courtesy of the main body of the galaxy. And that’s even with the current innovations we have such as x-ray and infrared spectroscopy. There is some region in space that is what we call the zone of avoidance. I bet you can work out why it’s called like that, but in case it isn’t that obvious yet, it’s the part of the night sky that’s hidden from us because of how we are positioned in the Milky Way. Or how the Milky Way is blocking our view. Depending on how you see things. Well, we could wait about 113 million years, where the rotation of the galaxy will finally bring us to the side where The Great Attractor is. If we can wait that long. Maybe a really smart dinosaur-eating large mammal from the same amount of time ago has seen what it actually is? We got to wait for a time machine to ask him ourselves. One suspect that could be the thing behind the mask of The Great Attractor was the Norma Cluster. A collection of galaxies located a bit around where the attractor is, having a binding mass of about a million billion of our Sun! Could this be the source of the great tugging force that we are looking for? There is another candidate that could be bearing the cape of The Great Attractor that’s located again in the zone of avoidance. Located about 652 million light-years away from Earth is the Shapley Supercluster: undeniably the largest collection of galaxies that we have ever known in the observable universe. Do You think the Norma Cluster has an amazing amount of mass? Well, this one has about 10 times of that! That’s one actual heavyweight! The Shapley Supercluster is so massive that it’s not expanding like everybody else around it. Instead, it’s collapsing towards its own center of mass. Remember how The Great Attractor that we are looking for might actually be pulling stuff towards it? Well, this habit of the Shapley makes it a candidate to its real identity! Another theory that scientists have is that The Great Attractor might actually be where dark energy flows and meets up in space. Of course, you know how difficult it is to prove this claim, as even dark matter or energy itself is something that’s within our very own understanding. The last thing that we know about the star is that it seems to be the gravitational heart of our home supercluster, the Laniakea. If we can make the supercluster an object, and we place it on our fingertip at the point of The Great Attractor, then it definitely would balance. So okay, let’s summarize the things that we know about The Great Attractor. It’s a gravitational anomaly. We don’t know if it’s an object or not. What we know is that it’s a region in space where all the gravity seems to be strongest as compared to anywhere else. It could be a supercluster. But there is no way we can observe it due to The Great Attractor, and all the suspects being located in a region in space that’s obscured to us by our very own galaxy, the zone of avoidance. One question that’s been bugging you is that is this going to harm us as a species in the future? Well, I’ll leave that one to you. What do you think? The universe is expanding, and it’s happening really fast. Even faster than light. So, there will come a time when the light from some galaxies will no longer reach our eyes. We will experience total darkness. There might come a time when we won’t be even to know for sure what exactly The Great Attractor is. That chance will be thrown out of the window for eternity. And all that we’re gonna be left with is what hindered us from knowing in the first place. All we’re gonna be left with is the Milky Way to observe and scrutinize. But let’s dig on that thought further. In the future, when this happens, the scientists of that age will base what they know about the universe on what they can only see, which are the items in the Milky Way. Ever thought of, what if the universe has already expanded by an unimaginable vast number that, all that we are left with to define it is whatever we can currently see? Ever thought that the reason we can’t understand a lot of things in our own universe is that we already missed the chance to see the actual bigger picture? Let us know what you think! Do you think we came in too late as a species, and that there is definitely a lot of stuff that we missed to see that would complete the puzzle of our understanding of the universe? 

You know the drill, guys. Let’s hear your ideas in the comments section down below! This one is a heavy mental jog, isn’t it?

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