The Universe: Exploring Alien Galaxies (S1, E9) | Full Episode

our sun is one of billions of stars in the milky way galaxy and our galaxy is one of hundreds of billions maybe a trillion in the known universe from the hubble space telescope comes a view of the universe that was a magnificent trip through the mists of history and back nearly all the way to the big bang each smudge each clump each blob of light a billion stars here a trillion stars there if you want to know our place in the universe take a look up and far far away to the realm of alien galaxies ours is a universe of motion expansion light and blackness we think the universe is about 13.6 billion years old so just to put that in context the earth and the solar system is just over 4 billion years old so the universe is just over three times older than the earth across the vast reaches of the interstellar void distant stars are held together by the long reach of gravity's unyielding grip over billions of years these stars have come together to form galaxies the galaxy is a collection of 100 billion or so stars and these stars are by no means touching each other or actually anywhere near each other compared to their sizes they're very very far apart from one another the thing that blows my mind about galaxies is what monsters they are they are incredibly huge if the sun were the size of a period on a page the dot of an eye our galaxy would be the size of the continental united states so they're gigantic astronomers have always known there was something special about the band of stars and dust that seemed to encircle the night sky above them it's our galaxy a white smudge they called the milky way that band of light is the collected light of hundreds of thousands of stars that you can't see individually with your eye and that was made by the greeks they thought it looked like a milky river so they called it the milky way there are 100 billion stars in our galaxy and there are a hundred billion galaxies in the observable universe that's more stars in the universe than grains of sand on the beaches of the earth if you imagine the galaxy itself is the size of a hockey puck then the galaxies are spaced from one to another about a few diameters apart so if there's a puck here and a puck over there that's kind of the way the galaxies are spaced in the universe pictures from the hubble space telescope show the wide variety of alien galaxies the sombrero galaxy also known as m104 one of the most massive objects in a gigantic cluster of galaxies the sombrero galaxy contains nearly 800 billion times as much mass as our sun compared to the milky way sombrero has a much larger bulge relative to its highly wound disc this image of the sombrero galaxy is also a prime example of what happens when three of the world's top space telescopes joined forces the chandra x-ray observatory taking an image of the high-powered x-rays emitted by the sombrero galaxy the hubble space telescope snapping an optical picture capturing the visual light that's made the multi-million light year journey to earth and the spitzer space telescope capturing an infrared version looking at the sombrero galaxy's heat signature melded together these three images provide a stunning and unforgettable look at a galaxy 28 million light years away m-51 the whirlpool galaxy its spiral arms twisting like cotton candy being spun the center of the whirlpool galaxy is so densely packed with stars anyone living on planets there would be under a constant bright sky day or night centaurus a a galaxy sending out massive amounts of radio waves think of it as an interstellar broadcaster beaming its signal throughout the universe all day every day it's the closest of the so-called active galaxies galaxies that pour out tremendous amounts of energy from their cores is the hubble ultra deep field image created using the hubble space telescope it shows us how truly vast and distant the universe really is and how those far-off spaces are anything but empty when you look very deep in the universe you're looking back in time so you're looking back at galaxies right back to when they were very very young when they were only a few percent of their current age so the hubble ultra deep field is really like a time tunnel that gives us a glimpse of galaxies as they were before the earth was in existence the earth is 4 billion years old we're seeing galaxies as they were 13 billion years old so the light left these objects before there was any earth at all the nearest large galaxy to ours the andromeda galaxy is about 2 million light years away so the light from the andromeda galaxy takes two million years to get here so we're seeing it as it looked two million years ago and that's one of the more nearby galaxies as we look farther and farther out in space then we're looking farther and farther back in time to get a better idea of the concept just visit one of the most spectacular vistas on earth the majestic grand canyon as you look down the layers you get older and older rocks and we can tell what the different environments were so we can actually look at the geologic history of this area over time and in essence look back through the environment that was located right here back over hundreds of millions of years of the earth's history so by looking at stars that are further and further away from the earth astronomers can get an idea of the evolution of the universe from the earliest days of galactic astronomy observers noticed galaxies came in a variety of shapes and sizes the two main types of galaxies are spiral galaxies like our milky way which have spiral arms in a thin disc and then elliptical galaxies which are sort of more spherically or elliptically shaped and they don't have spiral arms the spiral galaxies have a lot of gas and dust in them from which new stars are forming right now whereas the elliptical galaxies seem to have formed their stars long ago they don't have that much gas and dust so they're not forming stars right now there's also some irregular galaxies which generally have a lot of gas and dust but not in a nice spiral form detecting these far-off accumulations of stars is made easier when astronomers search for the streaming blasting beacons found near the center of many of them violent and erratic hearts beat at the center of many alien galaxies sending out so much energy they can overwhelm the amount of energy produced by all of the other stars within them these are the active galactic nuclei so we look at some galaxies and we find that they have at their very centers very powerful engines that are producing a tremendous amount of light we can tell that they're very far away and yet they're still very bright when we look at them so they must be tremendously powerful dumping a lot of energy out every second among the most violent and powerful of the active galactic nuclei the mysterious phenomenon called quasars when we look at quasars quasi-stellar objects and see how far away they are some of them are tremendously bright the brightest one of them is about a trillion times as bright as our sun spectacular streams of electromagnetic energy bright beacons lighting up the sky for billions of miles these high-energy sources provide a stunning reminder of the universe's power to illuminate a quasar itself can be brighter than an entire galaxy so when we look at a quasar like 3c273 the hubble space telescope took some images of this and we found that it has a big jet of material shooting out of the side of it almost the size of the galaxy itself these are really weird things these active galactic nuclei as active galactic nuclei show space is a violent place and as it turns out there's a massive collision going on right in our own backyard the culprit a galaxy called the canis major dwarf galaxy as the name implies dwarf galaxies are small making them even more difficult to detect now the canis major dwarf galaxy is taking aim at the milky way two galaxies on a collision course from which thanks to gravity there is no escape when a small galaxy comes too close to a large galaxy the tidal effects cause it to be stretched out and distorted so the gravitational attraction of the larger galaxy will actually pull and stretch the stars in the smaller galaxy so a collection of galaxies that has a relative spacing compared to their size about like the way these pucks are laid out on the ice all these galaxies would be moving through space with respect to one another but every once in a while one of these galaxies is going to bonk into another one now when that happens the shape of the galaxies would actually become distorted and stretched out pucks are solid galaxies are made of individual stars each of which feels the gravity of all the others and they become distorted and torn into tidal tales a big swooping arc of stars in either direction and that's how the once far-off stars from an alien galaxy blazing through space for millions upon billions of miles can end up blending right in with our own but what caused these stars to clump together in galaxies why has the matter and mass of the universe fused into these spectacular structures to find the answer we have to turn our clocks back millions and billions of years ago go back far enough and you reach a point where all the matter and space and time become compressed and compacted into an infinitely small point a gravitational singularity of infinite dimension it's a point that exploded with a spectacular big bang a long time ago the matter and energy that would make up every alien galaxy wasn't far away everything that ever became an alien galaxy sprung forth from a gravitational singularity that has come to be known as the big bang if you run a film of the universe backwards in your mind eventually you get to a point where the density would become extremely high if you go far enough all the mass and energy that we have in the universe would be in a single location and you would find infinite density we think that the expansion of the universe is telling us something very profound that the universe has a beginning point in time in those moments after the big bang the rules of our universe and stars took shape and one of the biggest rules was the law of gravity after the big bang the universe of course was expanding but there were some parts that were denser than others those denser parts started gravitationally contracting and they formed galaxies pockets of gas within those gravitationally contracting clouds formed stars because those pockets gravitationally contracted even more than the general cloud of gas it would take hundreds of millions of years for the first galaxy to coalesce into existence we don't know exactly when this happened but we can see pretty mature galaxies about a billion years after the big bang and the earliest objects that i can see at about 500 million years after the big bang so it's within this period that we think the very earliest objects switched on but we haven't yet found a time when there were no galaxies at all to learn more about alien galaxies we need to solve the many mysteries of our milky way's own place in the universe when we want to look at the structure of our galaxy the difficulty that we run into is that we're inside of it we can only see what we can see from inside moreover there's dust and gas blocking our lines of sight so we can't see very far from our position in our galaxy in many different directions we think the milky way is a barred spiral galaxy reaching about a hundred thousand light years across with a 3 000 light-year thick core most galaxies in the universe are smaller the milky way and many alien galaxies are like cities with a central dense core and less dense suburbs for spiral galaxies like our own milky way that means a trip to visit the burbs is not unlike a trip on the freeways all the stars in our galaxy are orbiting around the center we're about 30 000 light years away from the center and it takes us about 250 million years to make one orbit around the galaxy now the stars are all in their orbits they're all moving around the galaxy so what causes these beautiful spiral arms that we see well they're sort of a density wave an area where the stars in the galaxy are just a little bit denser more packed together than the rest of the galaxy different stars move into the density wave different stars move out but the density wave stays there and that's the spiral arm it's a lot the same way that traffic jams get started on the freeway something happens that makes maybe one star slow down some sort of gravitational interaction and other stars slow down in response to it and all of a sudden you've got a traffic jam so galaxies seem to naturally form these spiral density waves two and a half million light years away a menacing counterpart to our galaxy sits and swirls casting a wary eye toward the milky way it's the dance partner for our galaxy our biggest neighbor and our biggest nemesis it's called m31 better known as the andromeda galaxy the andromeda galaxy is about the same size as our milky way it's about a hundred thousand light years across it's a spiral galaxy it has perhaps a little bit less active star formation going on right now than our milky way but otherwise it's quite similar andromeda is probably also the product of several smaller galaxies that coalesced or interacted over time one of those galaxies may be responsible for andromeda's double nucleus two huge clumps of stars found at its center on earth we've been keeping an eye on our trillion star neighbor for centuries persian texts from the 10th century mentioned this small cloud in the skies but at the time there was no way of knowing that andromeda was an entirely separate galaxy two and a half million light years away that makes it the furthest object in the universe you can see with the naked eye while the milky way may be able to absorb the impact of a colliding dwarf galaxy a clash with the andromeda galaxy is not only inevitable but will forever change the local galactic landscape gravity the universe's most prolific power is the force that's pulling andromeda and the milky way closer and closer and someday in the far off future these two spiral titans will collide if you look at the milky way galaxy and the andromeda galaxy the nearest large galaxy to us they're actually approaching each other at a fairly astounding rate several hundred kilometers every second they're very far apart right now but in the next few billion years sometime they will be right up against each other and so a collision is in a sense imminent probably no stars will physically hit each other there's just so much space between the stars but when andromeda collides with us it will have a huge impact on the milky way some things will get thrown into the black hole in the middle some stars will get ripped off and thrown away into space so it'll be dramatic and the entire night sky will change the constant motion of alien galaxies and the time frames involved may be hard to comprehend andromeda is close enough to the milky way that their gravitational attraction brings them closer together but elsewhere almost all of the alien galaxies we see are moving away from us in our common experience like an exploding bomb everything explodes away from a center now is there an empty center to our universe are we on a shell of galaxies flying away from wherever the original explosion was no and that's the amazing thing in our universe space itself is expanding every little bit of space the space right here between my hands has a pressure to expand it's this expansion first detected by astronomer edwin hubble that laid the foundation for much of modern astronomy so the universe expands with time and space itself is actually expanding now if you take a one-dimensional example of the universe here here's a hypothetical universe where i've got these ping-pong balls which are the galaxies on this rubber hose i can expand that hose and all the galaxies move away from the others see that and in fact if we focus our attention on this one here the ones that are farther away from that move faster than the ones that are closer in because there's more space there's more tube between this one here and the distant ones than between this one and the nearby ones so that in a sense is a good model for hubble's observation that at a given time the more distant galaxies move faster than the nearby galaxies notice also that no galaxy can claim that it's the unique center of the universe sure from this one's perspective all the others are moving away but if i were to put myself on this one here i would say that all the galaxies are moving away from that one as well so no matter which galaxy you're on you see the others moving away from you that's what happens in a uniformly expanding universe there is no galaxy that can say that it's the unique center of the universe if you think back to earlier times it was thought that the earth was the center of everything was the center of the universe and the planets and the sun all orbited around the earth and the stars every day made one trip around the earth then we discovered that our sun was one of many stars and that our sun was cruising around in through the universe as we knew it but this discovery by hubble told us that not only was our planet one of many planets and our star our sun one of many stars but our galaxy was one of many galaxies presumably like any other it really changed our world view and our place in the universe to think that our galaxy is an ordinary galaxy so just what's in our galactic neighborhood meet the local group of galaxies a group with ever-increasing membership our local group of galaxies is a small group or cluster of about three dozen galaxies our milky way and the andromeda galaxy m31 are the two dominant galaxies most of the galaxies in our local group are small dwarf galaxies these galaxies each have collections of small satellite galaxies that are in their thrall that orbit around them and these big galaxies all feel the influence of each other's mass and orbit around each other so all of these galaxies the small galaxies are orbiting the big galaxies and the big galaxies are all sort of orbiting each other it's a group of about 30 or so galaxies that are all sort of orbiting around a common center of mass the most well-known dwarf members of the local group two galaxies known as the large and small magellanic clouds scientists now think the clouds orbit the milky way thanks to the tidal influence of our galaxy gravity of course is a two-way street it's believed the gravitational pull from these clouds has also distorted believe they are made of different stuff than our galaxy the clouds are richer in hydrogen and helium than the milky way and with fewer metals scientists think this means the stars are younger in the clouds the gravitational dance between the clouds and the milky way has likely been going on for billions of years but all the while a different and much more mysterious battle is going on back in the center of the milky way because when you head for the center of our galaxy once you get through all the dust and gas and older stars you'll find something so insanely frightening the normal rules of time and space do not apply for lurking at the heart of the milky way and perhaps every alien galaxy is a massive beast with a ravenous appetite a beast from which there is no escape there is a region at the core of our galaxy the milky way where nothing escapes this is the point of no return a super massive black hole a black hole is an astrophysical object that has so much mass in such a small volume that the gravitational force is so strong that even light doesn't have enough energy to escape it black holes can form either when a massive star explodes at the end of its life and the core of the star collapses into a black hole or you can have super massive black holes at the centers of galaxies how massive try nearly four million times the mass of our sun sometimes black holes swallow entire stars creating fierce explosions called gamma ray bursts in order to emit a gamma ray an object has to be billions of degrees in temperature or even trillions so we're seeing something incredibly hot in some cases the galaxies were as much as 10 billion light years away and the gamma-ray bushes had been so bright that if you had a pair of binoculars and you were actually looking at the right part of the sky at the right time you have been able to see a visible light afterglow from the gamma rays that's using binoculars to see something that's on the other side of the universe 10 billion light years away can you imagine what sort of explosion that was so if there's a super massive black hole at the center of our galaxy might similar black holes lurk at the center of all alien galaxies when we look at neighboring galaxies and this is a recent result we find that most galaxies appear to have very massive black holes in their center ranging from millions to even billions of times as massive as our sun it appears to be a very common ordinary aspect of the galaxy black holes swallow matter but less than one half of one percent of our universe is believed to be made up of observable matter such as stars planets gas and dust so what accounts for the rest of the stuff created in the aftermath of the big bang what really fills up alien galaxies scientists best guess is a mysterious substance called dark matter dark matter is fantastic stuff we know that it exists we know that it gravitationally pulls on things one of the best pieces of evidence for the existence of dark matter is that spiral galaxies are spinning more quickly than they would be spinning unless there were extra unseen material causing them to spin that fast caltech professor richard ellis has pioneered a new technique to create a three-dimensional map of the universe including the dark matter this is the first hint from dynamical data that there's a lot of dark matter in the universe we can also detect dark matter by a really remarkable phenomenon which was predicted by einstein and is now in great use in astronomy which we call gravitational lensing dark matter bends the light passing through it much like a curved piece of glass so light rays are bent by material and where we can see the signature of this bending of the light rays we can infer that there's a lot of dark matter present we don't have to see the dark matter directly it doesn't shine it doesn't scatter light but we can infer its presence from the effect it has on light rays that are coming through clumps of dark matter so we know that the dark matter is there we can make maps of how it's distributed even if we can't see it directly so one further advantage of gravitational lensing is it's just like a magnifying glass so when you look through it things are bigger and brighter than they would be if you didn't have it so if you think about it it's like a natural telescope in space while dark matter plays a central role in the birth and evolving life of galaxies there's another dark force partly responsible for their growth on a cosmic scale the galaxies are rushing away from us due to the continuing expansion of the universe so if the universe is expanding what's driving it the only answer scientists can come up with for now a mysterious dark energy dark energy is even stranger in some ways than dark matter dark energy is causing the universe to expand right now faster and faster with time this expansion set in motion at the universe's conception has accelerated over the last few billion years because the dark energy that creates the movement has increased over time by nature the gravitational force that binds galaxies together decreases over time as the space between them increases so instead of having a gravitational pull instead of slowing down the expansion of the universe dark energy is speeding up the expansion of the universe and it's been doing that for the past four or five billion years in perhaps a billion trillion more years the fate of the universe and the impact its black holes dark matter and dark energy have on mankind will finally be known when a star gets too close to the black hole at the heart of an alien galaxy chaos erupts that's one of the findings from the galaxy evolution explorer mission or galaxy the galaxy evolution explorer is an ultraviolet telescope that observes the universe at ultraviolet wavelengths and at these wavelengths you're very sensitive to studying young stars and star formation um in galaxies back to half the age of the universe billions of years ago however we also look in the ultraviolet for these luminous flares from when a star is swallowed by a black hole the star can't hold itself together anymore and it's ripped apart and the gas from the star plunges into the black hole some of the gas will be ejected from the system at high velocities but some fraction of the gas will plunge into the black hole and in that process will heat up to very high temperatures and give off a luminous flare of ultraviolet and x-ray radiation thanks to galax suvi gazari and other researchers were able to watch it all happen four billion light years away galax hubble and the spitzer space telescope will soon be getting a new neighbor designed to help capture images of alien galaxies the james webb space telescope is due to launch in 2013 designed to explore the infrared spectrum like never before using the webb telescope scientists hope to be able to see through the dust and stars that block our view of the milky way center and provide a more complete picture of not just our galaxy but of all alien galaxies the james webb space telescope differs from the hubble space telescope in two respects firstly it's more powerful it's a bigger mirror secondly it is actually working at slightly longer infrared wavelengths what hubble and webb have in common is the power to see beyond atmospheric turbulence that prevents astronomers from getting picture-perfect images from 99 of the sky earth's atmosphere is turbulent it blurs out images from stars so the earth had no atmosphere we would see stars as basically really perfect dots of light but what happens is that because as the light passes through the atmosphere it's distorted it turns into a fuzzy blob it turns out there's two ways to fix this one way is to go into space the other way is to instead fix the telescope on the ground so that it removes the effects of this turbulence and that's a technology known as adaptive optics adaptive optics measures the image of a galaxy by the way its light reflects off another lighted object like a nearby bright star to do adaptive optic sensing you need a very bright star because of course you're making measurements of the atmosphere hundreds or thousands of times per second so you need something bright to look at most stars are not bright enough to do this at observatories like keck in hawaii adaptive optics uses a laser beam to help create the light needed for the snapshots you can point it anywhere you want on the sky and so instead of looking at only one percent of the sky you can look at most of the sky with very very high resolution very sharp images in this way you can make images 10 to 20 times sharper from the ground than you could without adaptive optics it's just another tool in the kit of course designed to bring the fantastic reaches of alien galaxies back down to earth the universe of course is home to many things larger than our small planet earth larger than our solar system larger than our galaxy to think that our milky way is just one of hundreds of billions of galaxies in the observable universe it really makes you feel like you're a part of something much larger than our small planet earth like it or not this is our place in the universe a speck on a speck on a speck just one tiny blue-green oasis of life swimming in a vast ocean of alien galaxies you

Channel: HISTORY

Views: 362,829

Keywords: history, history channel, history shows, history channel shows, the universe, history the universe, the universe show, the universe full episodes, the universe clips, full episodes, life Forms Evolve in Alien Atmospheres, alien galaxies, life forms, alien forms, alien atmospheres, aliens history channel, season 1 episode 9, episode 109, The Universe Season 1, The Universe Season 1 Episode 9, The Aliens Galaxies Episode, galaxies, the universe history channel

Id: GTGXeob6VcI

Length: 44min 25sec (2665 seconds)

Published: Mon Oct 18 2021