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Our galaxy, the Milky Way, is big.
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Estimates put it at about 100,000 light-years, from one end to the other.
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But you know what's way bigger?
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Space itself.
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Because in all of that space we estimate that there are as many as 100 billion galaxies.
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And among all those galaxies, we've found a few that are our twins.
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That's right, the Milky Way has long-lost twins out there among the stars.
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Although not in a literal sense like our galaxies formed in the same place at the same time.
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But finding these twin galaxies can help us learn about our own, because it's pretty
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hard to figure out what's going on in the Milky Way while we're a part of it.
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The Milky Way's disk is 1,000 light years thick, and to get a good picture of it, you'd
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have to get pretty far above it, like how the Earth is round but you wouldn't see
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the curve unless you were way above it, even higher than commercial airliners go.
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And cue the flat Earthers in the comments.
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Considering that the Voyager I, the most distant man-made object we've ever made, is about 0.002 light-years
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away, we're not taking a galactic selfie any time soon.
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To borrow a metaphor I wish I'd thought of, mapping the Milky Way is like trying to
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map a forest while you're tied to one of the trees.
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So we've had to piece together what our galaxy looks like based on what we can see.
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First and most obvious is the Milky Way is flat because we can see it edge-on in our night sky.
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The shape of that flat plane has been a bit harder to pin down.
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The astronomer Herschel was the first to try it in 1785, and by counting the number of
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stars he saw and assuming that more stars meant more galaxy, he came up with a pretty blobby shape.
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This picture changed in the 1910s when another astronomer, Harlow Shapley, measured the distance
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to globular clusters of stars and found that they were in a spherical shape about 100,000 light years in diameter.
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Shapley concluded that our galaxy must be a circular disk inside this spherical halo of globular clusters.
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In the last 75 years, techniques that could see through interstellar dust like radio,
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infra-red, and X-ray astronomy have helped us see just where the arms of our spiral galaxy are.
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But there's only so much we can do from here.
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Exactly what the Milky Way looks like on the other side of its central bulge is unknowable to us.
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And our image of what we can see is still changing; we only started to realize the central
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bar connecting the large spiral arms was thicker and more substantial than we thought in 1996.
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So now that we have a pretty good idea what we look like, we can seek out similar galaxies that can fill in the gaps.
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NGC 1073, for example, is a barred spiral in the constellation Cetus.
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Another twin, GAMA202627 has two smaller companion galaxies, much like our own Magellanic clouds.
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Companions as big as these clouds are a rare find and warrant further study.
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We've even found a galaxy that could tell us about the Milky Way's ominous future.
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Near Andromeda is a small and incredibly dense galaxy called M32.
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A recent paper proposes that once upon a time it looked like the Milky Way, until Andromeda
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came barreling through, stealing stars and planets, ballooning in size, and leaving M32 a shadow of its former self.
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Why is this important you ask?
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Because Andromeda is on a collision course with our galaxy.
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What happened to M32 could be what happens to us.
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Odds are good that as our telescopes and techniques improve, we'll find more of our twins out there that can tell us more about ourselves.
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Just don't get too attached to the galaxy's shape, because in about 4.5 billion years, it could all change.
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Fun Fact: Confirming the Milky Way had a large bar also meant our galaxy had two large arms
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that wrapped around it twice, rather than four separate main arms as previously thought.
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If you liked this video, go check out this one Maren did on the universe's first type of molecule.
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Thanks for watching, don't forget to subscribe and I'll see you next time on Seeker!