The Dipole Repeller: The Void That’s Tearing Us Apart - Ask a Spaceman!

today we are talking about the dipole repeller which is a hypothetical void sitting hundreds of millions of light years away from us that might be pushing us into our next nearest neighbor super cluster now to map this out we it's actually incredibly challenging to make maps of the local universe and that's because we are sitting inside of the milky way galaxy and the milky way galaxy is full of dust and the dust blocks our view especially in the direction of the core of the milky way galaxy there's so much dust there's so much gas we have a very very difficult time piercing through that dust to see what's on the other side so we actually have a name for this region of the sky we call it the zone of avoidance which is a wonderful wonderful name and it's way less scary in reality than what it sounds like it just means this is a place where we have difficulty making astronomical observations beyond our galaxy because our own galaxy is sitting in the way the second reason that galaxy surveys or maps of our local volume of the universe are difficult to make is because well we have to look everywhere to do it to make these kinds of maps to to map out the largest structures in our gala in our universe we have to pinpoint very precisely the locations of many many galaxies now for a few galaxies this is relatively straightforward you find a galaxy you figure out its location on the sky you estimate its distance and you're done but to build out these kinds of maps that we're talking about you have to survey thousands of galaxies hundreds of thousands of galaxies millions of galaxies in order to make these kinds of maps complete now we do galaxy surveys all the time we have massive surveys that have cataloged millions of galaxies in the universe hundreds of millions of galaxies but these are typically of galaxies very very far away because you can build a telescope you can point it at a particular patch in the sky and you can collect all the light from that one particular patch where there isn't a lot of dust and you can stare at it night after night after night after night and you can pick up the very faintest galaxies the very smallest galaxies and then in that little region of space you can build up a catalog of millions of galaxies right over here that's great and we do that all the time but when we're trying to build a map of our local region of the universe that's not going to cut it because we're just going to capture galaxies in one little part and we're trying to build a map of everywhere around us so you have to repeat that exercise all across the sky and that makes it very challenging plus you have to deal with all the dust and so our knowledge of the local universe is less complete than you might otherwise think it is because it's actually very very challenging it's it's in this i don't know what the reverse of a sweet spot is but it's an anti-sweet spot of mapping the universe we can map our our milky way galaxy and the stars in the milky way galaxy with one set of tools and one set of techniques and we can map the very distant parts of our universe with another set of tools and another set of techniques but mapping the local volume of our universe we're talking now to like one or two hundred million light years here is extremely challenging but we have made some progress so let me build this map for you let's paint this picture so we can set the scene for the dipole repeller we start off with the milky way galaxy this is our home galaxy home to a few hundred billion stars it's about a hundred thousand light years across to give you some sense of scale our next nearest neighbor proxima centauri is about four light years away from us so the whole galaxy is 100 000 light years across sitting two and a half million light years away from us is the andromeda galaxy that's the next nearest major galaxy to us it's as big or probably bigger than the milky way galaxy itself probably home to around a trillion stars probably a little bit more massive it's big two and a half million light years away these two galaxies along with a third much smaller galaxy that nobody cares about called triangulum make up the major galaxies of what we call the local group the local group is about uh 10 million light years across give or take depending on how you define it and it's made up of the of these three major galaxies and then dozens over 80 known smaller dwarf galaxies like the magellanic clouds that orbit the milky way there's a whole bunch that orbit andromeda there may be a few that orbit triangulum all together we make up something called the local group this this is our neighborhood on the cosmological scene the next biggest thing that sits near us is a ring of galaxies of around a dozen galaxies that sit around the local group these things these of these galaxies are given the name of the council of giants because it looks like they're they're talking about us uh but they're really not it's just cool name again another very very cool name local group not such a cool name but that's a different story the next nearest big thing to us is the virgo cluster the virgo cluster sits about 60 million light years away from us and it itself is a few million light years across home to one to two thousand galaxies it is definitely the the largest nearest thing to us it is a cluster both groups and clusters are gravitationally bound which means the mutual gravity of all the galaxies and gas and dust mat dark matter inside of those objects keep them glued together so we have our local group the local group is near the virgo cluster surrounding the virgo cluster are many many other smaller groups we are all moving towards the virgo cluster and that motion is going to come important later when we untangle the dipole repeller we are part because we are near the virgo cluster we are a part of the virgo supercluster complex now the word supercluster doesn't have a strict definition it doesn't have a strict meaning in astronomy or cosmology different groups different researchers will have different definitions of the word super cluster the word super cluster itself will change over time as we get a better understanding it's it's like the analogy i like to use is is what is the metropolitan area of a major city yes you have the the city limits that's the edge of the city that's the edge of the virgo cluster but if you're living just outside the the city limits but you work in the city you commute to the city you you go to restaurants and movies in the city are you really a part of the city kind of sort of yeah and it's a little bit of a fuzzy definition so the super cluster has a very fuzzy definition we are a part of the virgo super cluster because we are headed towards the virgo cluster the gravity of the virgo cluster is pulling us and andromeda and the entire local group and all the other surrounding groups towards it and so that's one way to define a super cluster is what is the area of influence of a cluster but it doesn't stop there as we zoom out from this picture of the virgo cluster in its supercluster environment all the local groups or all the groups surrounding it as we zoom out we start to pick out more clusters these plot clusters and other smaller super clusters are themselves a part of a larger super cluster called pisces cetus super cluster this super cluster which is made of many many many clusters and many many groups is itself one long filament of an even larger super cluster that was only recently discovered called blania kaya so if you imagine the virgo super cluster looks like a little twig the pisces ceta super cluster looks like a branch and then laniakea is a big branch that we're all a part of next to the lanius chaos super cluster which is our local super cluster are other super clusters there's there's no such thing as a super super cluster or a super duper cluster or however you want to call it there are no larger structures in the universe because our universe hasn't had time to build those kinds of larger clusters and so what we see at the very largest scale when we're zooming out to hundreds of millions of light years individual galaxies lose their definition and you're left with this interlocking set of super clusters just these filaments and walls that make up one super cluster and then next to it is another set of filaments and walls and another in another at the very largest scales our universe looks like a web we call it the cosmic web this is the largest pattern found in nature it's the largest structure found in nature it is made of galaxies it is made of clusters it is made of super clusters one way to think about the cosmic web is to imagine a foam in a bath and you're looking at this giant network of foam of all these intersecting soap bubbles in the vast spaces in between you have the voids the empty pockets in the foam and then you see all this like network of connected walls uh and filaments all connecting to each other and locking in with each other and those are the super clusters again we don't have a strict definition of super cluster except a chunk of the cosmic web and so at the very largest scales you're left with super clusters and you're left with voids next to the laniakea super cluster which is our home super cluster we have other super clusters like the leo super cluster uh the hercules super cluster the the uh perseus pisces super cluster i had to cheat and look at my notes for that one we have all these names for our nearby super clusters beyond that there are more super clusters it fills up this our universe but we don't have names for those because eventually we just run out of names and they're just catalog designations or they may not even have a name at all sitting directly behind the super club uh the laniakea supercluster so we are on one side of laniakea laniakea is sitting here we're kind of at one edge of it on the opposite side of laniakea is the super cluster called the shapely supercluster and the shapely super cluster is is our local direction of motion we are moving towards andromeda because our local group is contracting and in a few billion years we will collide with andromeda our local group itself is moving towards the virgo cluster and on all the groups that surround the virgo cluster all the groups that make up the virgo super cluster the virgo metropolitan area are moving towards the virgo cluster the virgo cluster itself is moving towards the center of laniakea a location that's dominated by something called the norma cluster that's the heart of the laniakea supercluster and all the objects in laniakea are moving towards that center and then laniakea itself is moving somewhere else it's moving in the direction of the shapely super cluster so you may have heard of something called the great attractor the great attractor is the center of the laniakea supercluster that is the local center of movement the local gravitational well that we're all falling towards but some recent galaxy surveys have revealed potentially that in addition to all of our movement the collapse of the laniakea supercluster to its heart to the norma cluster which sits in the center there is an additional motion where the entire everything in laniakea is moving towards the shapely supercluster we call this the shapely attractor there is some massive cluster in there that is dominating this region of the universe and the flow and the motion of everything in the universe in this patch of the universe towards the shapely supercluster all this is fine and dandy but we've started to make maps of the shapley supercluster and we've started to make estimates of its mass and something isn't adding up you can add up the mass of of the normal cluster of laniakea and it accounts for all of our motion in that direction but this extra motion towards the shapely attractor towards the center of the shapely super cluster there isn't enough stuff but potentially there isn't enough stuff in the shapely supercluster to account for our motion in that direction so this is where the dipole repeller comes in because there's a pole a gravitational pull towards the shapely supercluster but to completely account for our motion it seems like there is a push from the opposite direction and this is what we think is the the dipole repeller it seems we have the shapely super cluster over here the laniakea supercluster over here where we're on one edge of it on the opposite side from the shapely supercluster we're over here and then it looks like behind us there may be a giant void that's right avoid we think the dipole repeller is a void it's called the dipole repeller by the way because we're being pulled towards the shapely supercluster over here and we're being pushed by whatever is back here and so there's two pulls a pull and a push uh a two pole dipole dipole repeller we think it's a void now how can a void push a galaxy there are two ways that nothing can exert a gravitational influence the first way is if you take imagine just sprinkling galaxies randomly throughout the universe and if you're in any one random spot in the universe you'll feel equally pulled in all directions because there'll be a gravity a galaxy over here and the gravity won't want to take you there there'll be a galaxy over here the gravity will want to take you here there'll be a galaxy down here the gra its gravity will want to take you and all of it balances out so you end up not moving now imagine carving a hole in that pattern of galaxies and you put yourself right on the edge well if you're right on the edge then galaxies in front of you will pull you with their gravity but galaxies behind you won't because there's nothing behind you it's a void and so you will feel an effective push because there's a lack of gravity behind you so you get an extra nudge this is one of the ways that the dipole repeller this massive void sitting behind us can push us the other way is through dark energy see dark energy is the accelerated expansion of the universe the biggest cosmological scale is that the expansion of our universe is accelerating it's getting bigger and bigger faster and faster every day this is a repulsive gravity gravity can be repulsive gravity can push under the right conditions and when you go into avoid one of these giant voids there's nothing there there's no gravitational attraction there's only dark energy the voids in our universe are actually pushing they're actually expanding they're actually inflating in fact the voids are where the accelerated expansion of the universe is happening because there's nothing else to counteract that balance of of accelerated expansion from dark energy so the voids including the dipole repeller can literally push on their edges and give everything around them a nudge now we know we don't know for sure if the dipole repeller actually exists it's based on these observations of motions and the the maps the very very scant maps that we have of our local volume of the universe but if the dipole repeller actually exists it is a giant void at least 100 million light years across might be a super void although it's debatable if super voids can even exist whatever it is is a giant empty patch on the opposite side of our universe from laniakea and from the shapley super cluster i wouldn't go there because there's there's not a lot of great restaurants there's not a lot of gas stations it's a cosmological desert that's what a void is but that's a different show thank you so much for watching and i will see you next time go to patreon.comsutter to help support this show

Channel: Dr. Paul M. Sutter

Views: 15,125

Keywords: space, cosmos, universe, astronomy, physics, astrophysics, cosmology, science, dipole repeller

Id: ciud4O5KAUw

Length: 17min 54sec (1074 seconds)

Published: Wed May 04 2022