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Get ready for a “crash course” about the Cosmos! Astronomers believe that in 4.5 billion years, a powerful galactic collision will occur, and we, or our descendants, will have a chance to see it! The Milky Way galaxy, which is the home to our Solar System and the very planet we live on, will collide with the Andromeda Galaxy. Sounds exciting, right? But it looks like it won't be the first time that the Milky Way collides with another galaxy! But let's start from the very beginning. Bang! No not that far back. In 2018, the European Space Agency finally released the most detailed map of the Milky Way galaxy and the neighboring stars! All this became possible thanks to the Gaia mission, which is a super precise space telescope. It was launched in December, 2013, with the ambitious purpose to draw a 3D map of our galaxy. Since the telescope started its work, it’s collected tons of information, cataloged over a billion stars, and calculated the distance and the motion range of more than 2 million stars. But that's not all. In 2018, astronomers were scratching their heads, looking at new data received from the Gaia mission. It seemed like the telescope had just discovered a new galaxy orbiting the Milky Way! It was named Antlia 2, and baffled astronomers to no end. First, the newly discovered galaxy was incredibly huge. It’s about the size of the Large Magellanic Cloud, another satellite galaxy of the Milky Way, which reaches a whopping 14,000 light years across! But at the same time, the Antlia 2 is very faint - 10,000 times fainter than the Large Magellanic Cloud (aka LMC). On top of that, it's extremely diffused and well-hidden by the galactic disk (which might be the reason why it hadn't been detected for so long). But it seems I'm getting ahead of myself once again. The thing is that galaxies get orbited by other, smaller galaxies just like planets get orbited by their moons, and stars get orbited by planets. Our home galaxy, the Milky Way, also has several of its own orbiters. Unfortunately, the only satellites you can see with the naked eye are the Large and Small Magellanic Clouds. As I've already said, Antlia 2 is too faint for you (or even the most experienced astronomer) to spot, but it might have influenced the Milky Way much more than scientists previously thought. Recently, a new study claimed that the very same Antlia 2 is responsible for bizarre ripples disturbing the hydrogen gas in the Milky Way's outer disc. The astronomers who conducted the research believe that the disturbances you can see these days could have been produced when the Milky Way collided with Antlia 2 hundred millions of years ago! By the way, even though astronomers have known about the ripples for several years, thanks to Gaia, they managed to see this phenomenon in greater detail. On the other hand, before the space telescope transferred the information about its discoveries to Earth, scientists didn't connect the Milky Way's hydrogen gas activity with Antlia 2. Nope, there were other theories. In 2009, astrophysicist Sukanya Chakrabarti and her colleagues concluded that there was a dwarf galaxy located right in the area where Antlia 2 was later discovered. Then, after the new data was received, the team calculated the trajectory Antlia 2 was bound to have in the past. They conducted several simulations, and voila! These simulations produced not only the current position of the dwarf galaxy, but also the ripples caused by the collision of the two galaxies. Before this research, another group of scientists had stated that the agitations on the outskirts of the Milky Way resulted from our galaxy's interaction with another of its satellites, the Sagittarius Dwarf Spheroidal Galaxy (Whoa, what a name! I’m not saying that again!). But later, it turned out that the gravity of the “Long name I won’t say” Galaxy wasn't strong enough to cause the ripples or influence our galaxy in any other way. On top of that, it seems that over time, the Milky Way has absorbed loads of the material Antlia 2 consists of. Admittedly, some of this material could be transferred via tidal interactions of the dwarf galaxy with the Milky Way. But the rest of the material could have been absorbed by our galaxy when the two collided about 1 billion years ago. If this theory turns out to be accurate, astronomers around the world will be over the moon. And no wonder: this way, they’ll be able to trace the history of Antlia 2, and probably get some answers to the dark matter question! The dwarf galaxy's weird diffused state can mean that there’s dark matter present in that region. If it's true, the region is likely to turn into a unique space laboratory for Earth's scientists to play in! But in any case, the next time Gaia will release new information is in a year or two. When it happens, astronomers will hopefully be able to draw the final conclusions. But let's talk about the collision that, according to astronomers, is yet to happen in several billion years or so. At least we have some time to brace for the impact! There might be not one, but two galactic collisions; and the first is likely to happen around 2 billion years from now, when the Milky Way collides with the Large Magellanic Cloud. This spiral of stars and dust is hanging out there somewhere, 200,000 light years away from our galaxy. And although right now you have nothing to worry about, in approximately 2 billion years, the two celestial bodies are likely to collide. So put that down on your calendar. I think it’s a Tuesday… And what a view it's going to be! Imagine the Milky Way nearing the smaller galaxy. The supermassive black hole residing in the center of our galaxy wakes up and starts to gobble up the LMC's stars and gas clouds with eerie enthusiasm. Thanks to this new food, the hole grows 8 times bigger than it is now and probably even turns into a quasar, which is one of the brightest things you can find in the Universe. Here, on Earth, people are standing still, dumbstruck by the sheer beauty of this phenomenon. Cosmic fireworks are coloring the sky, and our newly awakened black hole is emitting long jets of super bright radiation. If the black hole does turn into a quasar, it’ll be an even more breathtaking view. The thing about these celestial bodies is that their light can be up to 10,000 times brighter than the light coming from the whole Milky Way galaxy! That's why the Earth's night sky might get a new shiny decoration. But that won't be the end of it. The newly born quasar will get rid of some stars and send others flying billions of miles away from their orbits. As a result, all the constellations, as we know them, will disappear from the sky after the familiar stars get too far away for us to see with the naked eye. But hey, don't get so upset! The good news is that the collisions, and the potential appearance of a quasar, will have no effect on our planet! What's more, even the quasar's radiation won't manage to disturb the peace of the Solar System. And the chances that the Sun will get knocked out of the Milky Way are infinitesimal. Which means very small. But how about the collision with the Andromeda Galaxy? Will our Solar System survive this catastrophe as well? Right now, the Andromeda Galaxy is nearing the Milky Way at a speed of 68 miles per second. As you may guess, it's very hard to figure out its actual speed, and until 2012, researchers hadn't been sure if the collision was going to happen or not. Unfortunately, it turned out that we had to prepare for the appearance of Milkdromeda or Milkomeda - a structurally new galaxy, consisting of the merged Andromeda and Milky Way. On the other hand, such collisions aren't something out of the ordinary if you consider the super long lifespans of the galaxies. Besides, even though the Milky Way is home to more than 300 billion stars, and the Andromeda Galaxy contains more than a trillion, the chances of several stars colliding during the galaxies' merge are really low. The reason for that is simple: stars are located too far away from each other. For instance, the closest to our Sun star, Proxima Centauri, is more than 4.2 light years away, which is about 30 million diameters of our Sun. In simpler terms, if the Sun was the size of a ping-pong ball, Proxima Centauri would be the size of a pea located 680 miles away, and the entire Milky Way would be 19 million miles wide. As for other stars, can you imagine ping-pong balls hanging in space every 2 miles? Great, now you have a miniature model of our galaxy! Anyway, returning to the collision with the Andromeda Galaxy: there’s a 50-percent possibility that it would move our Solar System three times farther from the galactic core than it is now. But, if 4.5 billion years from now, there’s still some life on our planet, it won't be affected by the collisions in any way. And if that becomes a problem for you then, come see me, and we’ll work something out. But we’re going to be really old… Now it’s your turn. What are your ideas about the collision of the Milky Way with another galaxy? Let me know down in the comments! If you learned something new today, then give this video a like and share it with a friend. But – hey! – don't get all star-struck just yet! We have May posts for you check it.
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