Pulsars, X-Ray Binaries and Kilonovas (Intro Astronomy module 10, lecture 4)

hello everyone this is Jason Kendall welcome to the next of my introductory astronomy lectures this time we're continuing our study of neutron stars and exceeding how we actually observe neutron stars because they're really tiny so how do we even know they exist and that's the real question on today and there that's what we're gonna talk about is how we know neutron stars exist and they're known by the name of pulsars so let's go back and again look at what we learned from a neutron star last time which was it's really small it's really dense it's kind of like an atomic nucleus all on its own it's the magnetic field is extraordinarily large and the escape speed is nearly the speed of light light bends around it and if you drop something from a meter above it look it will it will hit the ground with an explosion that would be the growing of many nuclear bombs so yeah these are extreme extreme objects and deep in the core they might be quark type states there's these weird pasta-like States and it's very strange but the and they're forged in the moments of of an enormous enormous explosion called a type 2 supernova all right so let's look at how they were discovered they were discovered by accident in 1967 when Jocelyn Bell who's a grad student under Anthony Hewish who was her advisor and they were looking for very rapidly pulsating radio sources and what they were doing is they were hunting for there was hunting for oscillations in the solar wind so their study was the solar wind so they set up a series of radio antenna arrays at a big big big field and watched for the watched as the Sun went overhead and they'd looked for and they watched the sky to see what was the what them scintillations were at revealed frequencies and so they were looking for very short period variations because they're looking for scintillation of due to the eight due to the solar wind and so they were taking really fast samples and trying to actually do a big amplification on top because it's basically a big radio an amplifier and what they found was they found that something was pulsing so they found a pulsar that was pulsing at about about a mill second or Ones millisecond long pulses these tiny tiny tiny pulses once every second or so an a very very repeated rate and what happened was is that they just thought this was an amazing amazing object and Anthony Hewish even though well Jocelyn Bell actually discovered it she was pouring through the data and the reason she discovered is because they left the array running overnight and when the Sun wasn't in the sky they found something that was doing this pulsing this regular regular pulsing in the sky and in fact the technology for it existed but just nobody had ever done this kind of study before so they didn't know what they found so she did the analysis she made the discovery but because she was a graduate student under dr. Hewish who was running the entire experiment I he got the Nobel Prize and she did not now this is an interesting little study case study and the nature of things but really even Jocelyn Bell results said look this wasn't worthy of a Nobel Prize for me to get and in fact she said that later on after he won the Nobel Prize that the the point was is that he would get all the blame if it didn't if it fell apart so he gets all the blame so he gets all the credit and they were just people working under him it's not like it was her idea to start the entire project it was his so but yet still people think of people always still remember at Jocelyn Bell is the graduate student that got passed over for a Nobel Prize anyway her discovery and and subsequent confirmation by others showed that there were these radio pulses that occurred in very very very short pulses on extremely repeatable rates so what they've discovered is that this could actually be explained by a pulsar and they called them pulsars and the thing is is that they say well they're rat so we explained this by saying they're rapidly spinning magnetized neutron stars and so they're the magnetic Thea's so they actually they actually tried to determine what the heck these pulses were and they said well we've learned about variable stars so I could say could it be a star that's pulsing really fast like in and out like like getting bigger and smaller bigger and smaller so do these and there would be no known mechanism for it actually collapse back down until they decide taught of many other possibilities maybe it's a fast rotating planet or a me a fast moving object or maybe little green men that was one of the initial ideas was that now maybe it's an alien signal but when they found others they said near it ain't that so they actually tried to figure out what it could possibly be and they said well what if it's an actually a rotating star with a hot spot I think thought well this is extremely bright I extremely fast rotation and they determined that the odd that an object that was very distant distant enough to actually glow in this type of way and he meant the kind of radiation they found he would have to fly apart in order to the object which would spin itself apart there was no known astronomical object other than a neutron star that could actually hold itself together and spin once every millisecond which is what they found later is that there are millisecond pulsars so maybe 10 times or 100 times a second or 20 tens of times or maybe a few times a second and the only thing you could hold itself together as a neutron star everything else would literally fly apart and so what you have is you the the model of such a spinning object is you have a very strong magnetic field and the magnetic field creates beams of radiation as the electrons themselves spiral around in the magnetic field and are accelerated from the surface of the neutron star all the way out along the magnetic field and as they do so those hot spots them have become beams because the electrons then drop the emit their radiation because of synchrotron radiation which we talked about previously and synchrotron radiation means that they are spiraling at nearly the speed of light in an extraordinarily strong magnetic field and so that is beamed and so these became beams and the magnetic field of does not have to be aligned with the spin axis just in the same way the Earth's rotation axis is not aligned with this magnetic field axis I then in the same way a neutron stars magnetic field is not necessarily line with its spin axis so if we are in the direction of one of these beams then we see a blip we're not in the direction of the beam that we don't see a blip and that's that so the this particular thing would create enormous bright spots in optical radio x-ray and gamma-ray it would spit it would make a make a make light and all of them so we find this here's a better axis but our concept of it so the magnetic field lines are attached to or it come are part of the neutron star the spin axis is up-and-down the equatorial plane goes left and right and the magnetic field is misaligned so the red arrows demonstrate the radiation that's coming from both the hot spot as well as the electrons and part and even ions are spiraling in the magnetic field at nearly the speed of light and emitting synchrotron radiation it is thought that the magnetic field would be so strong at the surface of the neutron star at those hot spots that it actually lifts them electrons off of there and the act of lifting that releases energy in the form of light now you'll notice that the neutron star can spin pretty fast like milliseconds and some of them as we saw in the last episode can spin maybe a quarter of the speed of light but that means the magnetic field has to spin that fast and so the magnetic field itself at the edge in the boundaries there must be some boundary where the magnetic field the tips of the magnetic field away on the equatorial plane are going around at the speed of light because if it's fixed in there those magnetic fields don't get are not don't get dragged there they're kind of like there's the field lines they move with it so they must rotate so at some point the magnetic field must rotate around at the speed of light and that's where the the pulsar becomes a wind because now the magnetic field breaks down and then the electrons and things can spiral out along those wind like lines going left and right or along the equator of it and that can fling electrons out at nearly the speed of light and ions out nearly the speed of light on unconnected magnetic field lines so the magnetic field is very strong nearby and it's a very disruptive magnetic field nearby just like we talked about the Sun with with the solar wind this is just that on ultra ultra 10 to the 15th 10 to the 30th steroids that's what that is so the hot spots are where the electrons get lifted because of the strong magnetic field they emit light and they also spiral in a magnetic field and form the beams of radiation that we see as a lighthouse and so here's an example of a pulsar that has its magnetic field rotating and so the beams are coming out of the hot spots and so what we're gonna do is we're gonna follow it as it rotates faster and faster the electrons make the trace out the field lines as they spiral around and emit light a synchrotron radiation but the neutron star itself is hot remember it's about a million degrees million Kelvin so it's insanely bright and now as it passes in our direction we see a bright spot a pulse of light that comes from the Pulsar but only if we're right in the line of that and I'm sorry if that triggered anybody you know maybe somebody's got some kind of crazy thing going on where they can't actually look at that stuff but we see that the magnetic field is is an integral part of the Pulsar model and so there's our picture and much more artistic rendition with the electrons spiraling on the blue bang-bang fields but the merit really the magnetic field wouldn't be like blue like this it would be a cloud as that would be a real mixed-up cloud that would almost be rigid you would actually expect the total energy density in that to be so strong then how much material would be cruising along in it that those field lines would actually feel rigid they would hit you and they would actually have so if you were there another one of the next million ways to die is that if the field lines smacked into you you would be whacked and sent along in a very very in quite a pitch to the into the cosmos as it smacked into you so those magnetic field lines look gossamer but they would actually be almost solid that's an interesting thought so here's another version of what we would see maybe the effect of a pulsar on a supernova remnant remember these are formed as a result of a type 2 supernova as a supermassive star explodes and so the Pulsar itself it rotates around generates an enormous magnetic field the beams of light carry huge amounts of gamma rays the gamma rays then illuminate and excite the material around them causing the supernova remnant to glow so many of the supernova remnants that we see and mobile and talk about later actually are glowing as a result of the magnetic field energy that's being pumped into them from this tiny tiny tiny source so the supernova remnant that we see there might actually be a light year or two in size however the club and a light year is 10 to the 13th meters right but the neutron star is only about ten or so kilometers so that dot that's in there is actually completely invisible actually it's not invisible because it's extremely hot so it's emitting x-rays and optical light so we get this tiny tiny tiny thing that's exceedingly hot and emitting huge amounts of light and energy all right so because they do that pulsar is evolved and we don't see them of course if their jets aren't pointing our way and pulsars will radiate their energy way very rapidly and that that's because the end of the magnetic field will it will cause the light to occur and if it's emitting light it's losing energy if it's losing energy then it must slow down because basically this is one big dynamo and so we can think of it as in just the same way as how do you get power out of kind of out of a hydroelectric dam well you basically put a whole bunch of magnetic turbines and the turbines that the water flows over are bar magnets and so you just spin the bar magnets and if you spin a bar magnet you generate electric current when you generate an electric current that makes that hot spot in the neutron star that's what we see is a generated current from a magneto limit from a dynamo effect but then you the Dynamo that creates electricity so literally the water imparts some of its energy into the fan into the spine into the into twelve parts a significant amount of energy into the paddles that it goes down through a hydroelectric dam and it spins those things up really fast and so basically we convert gravitational energy potential energy into electricity and that's how a hydraulic dam works and that takes makes the water fall slower after goes down the dam and across those things in just the same way the energy that is released by the Pulsar as it spins means the pulsars spin slower as they age as they lose rotational energy when they're young they're fast and they're old they're slow and so if they're slow they don't do the pulsing dance and they don't it and they don't have as much as strong as strong a magnetic field that starts to weaken and that base it well they still could have an incredibly strong magnetic field but there's no rotational energy left in order to drive a dynamo effect so older supernova remnants are almost undetectable however they're found all over the sky and this is from the Fermi Space Telescope looking in gamma rays and so these are radial pulse ours found with the width that are part of the Fermi unidentified sources so Fermi Space Telescope goes out and looks for gamma-ray sources and what we can do then is come collate those gamma-ray sources with radio sources and that's what's been done here and all those little circles are discovered discovered pulsars inside of the inside of from the from the gamma-ray sources from Fermi gamma-ray telescope in the sky so this is an all-sky view showing a series of showing a series of discovered locations in this guy four pulsars so they emit both cameras and radio as well as optical light as well again as they get older and older they get cooler and cooler and so when you have isolated neutron stars in which they will be after time because the supernova remnant that that year that came out of them as they exploded spreads out into space seeding other stars making helping clouds make planets and things but the neutron star gets left behind it's all by itself and sometimes you can actually be there's maybe a chance that one can actually see them and so this is something this is nicely neutron star found by the Hubble Space Telescope and looking at it with also a couple of X Street with extreme ultraviolet Explorer which it looks and UV and x-ray from row sat to actually confirm yes this actually is a pulsar and trying to figure out how far this one is now you're getting the distance to something would allow and knowing its brightness we'd be able to get you get you the size so this is pretty good that it's in front of some molecular cloud that's about four hundred light years away so it's got to be closer than that and yet it's incredibly incredibly hot because it's emitting mostly in the x-rays and it's really really really small because it's so dim so if it's twenty fifth magnitude visual invisible light which is which is almost on the boundary of what Hubble Space Telescope can actually find and it's only four it's less than four hundred light years away it has to be insanely small about a few miles across in order for it to be in order for it to actually be visible to us so any isolated neutron star that we would not actually be able to see in x-rays and optical light is probably very is actually relatively nearby which leads us to think that there is probably hundreds of millions of these neutron stars orbiting the Milky Way because there's a lot of metals meaning gold nickel iron and other heavy elements all up and down the periodic table that were produced in supernovas so there has to be a lot of these things luckily the Milky Way is really big and these things aren't necessarily ever going to come into the space of the solar system and the Earth's is four-and-a-half billion years old and the chances that a neutron star will pass inside the solar system are practically zero so we're probably safe even though there's hundreds of millions of these things out there that's wild thought that even that was is nothing and so as one looks at the size scales of the cosmos that makes more sense but this gives you an example of just like well these things are really so far away that we would never actually encounter them all right so can we actually encounter a supernova or neutron star and the answer is kind of and in the hiss in history we did talk about some supernovae in the past on July 4th 1054 a new star appeared in the sky it was brighter than Venus were almost to e4 over - about two years greater than oh yeah almost two years and was even seen by the Anasazi so on the right we see what the vision is from Chaco Canyon and they lay anaglyph from ancient from ancient Chinese astrologers who were way back in 1054 also documented it there are other documents as well but these are cool pictures I chose to show to you and the Crab Nebula kind of looks like this on the bottom that's today's view of the Crab Nebula supernova remnant and in the center of it is a pulsar and we see the image of it pulsing above and that pulse is happening this is this is happening faster than that but we're actually looking at in an optical light or infrared light so we can actually get a picture of it and that means we're kind of looking at in the kind of strange way you know how you can kind of see a helicopter blade going backwards if you flash a strobe at it or if you have some something moving in a circle really fast in here a strobe at it or just look at it with like with like an an overhead an overhead fluorescent light bulb which has that buzzing sound that makes a definite flicker so the flickering allows you to see it so this imaging says we take a series of pictures rapidly in sequence with a definite with a definite space between them and hope we can catch these things so this was actually caught and it actually does have that double pulse so there is actually a two pulse to pulse for this neutron star in the center of the Crab Nebula now the Crab Nebula itself is emitting huge amounts of x-rays and gamma rays and it is this the brightest x-ray source in the sky in fact when people talk about x-ray sources or they say they've actually measured in terms of crabs so how many is it a milligram Laura says that a macro is at a micro Crab source is a demi crab source because the Crab Nebula is the brightest thing in the sky and so every other x-ray source can be measured in terms of how bright is it to the crowd it's kind of an interesting way of thinking about it so the Crab Nebula is the brightest object in the sky in x-rays and it's located pretty close at about 6,500 light-years away and the diameter of that whole thing is about 11 light-years so this one little neutron star a neutron star that's only about 10 miles in diameter is actually pumping out so much energy that it can illuminate and cause to glow an enormous cloud of expanding gas that's that is that's part that's from the shredded the shredded supernovae of that star back in 1054 and the speed it's going is almost 1,500 kilometers per second so this has actually been measured to actually go to actually to actually see the motion so Hubble Space Telescope keeps revisiting the Crab Nebula and we can see the clouds and move with time and we see also that the Crab Nebula can be measured at going about 30 times a second so that's really fast to have something really small rotating that quickly and this is interesting this Crab Nebula image because if we go then look at multi wavelength versions we took the image that we had before and we call it a different color so now we're mixing three different colors of light and the yellow whis penis that we saw is the image that we just saw just converted into black and white and then colored yellow the red sort of ambient glow is infrared light from dusty material and then the purplish glow in the center is due to x-rays and that's the x-ray emission that purplish glow in the center which actually seems to have a slightly different structure but there's actually but it even seems to be pushing these cavities around so you can see the x-ray glow seems to be pushing cavities around him and making bubbles and holes and this combines the vert the the x-ray data and blue is from the Chandra x-ray telescope and the red is from the Spitzer infrared Space Telescope and of course the yellow is the Hubble Space Telescope now the neutron stars we saw that from the lighthouse model that it's creating this enormous enormous magnetic field which is shooting particles out all over the place and let's see what that actually looks like because the Crab Nebula itself that central region that's glowing in in the in in x-rays has a central disc and a couple of jets and there's like this twisty jet that's coming from the center and that bright dot right in the center that's the neutron star and it's and we can actually get a picture of this with the Hubble Space Telescope now the Crab Nebula itself is a very very tiny image in the sky and this is a tinier yet image it's only a few it's only a it's only a few tens of arcseconds tens of architectures across but still what we see is that there's this wispy typique structure and there's these they're merging to form these rings so there's an inner ring that's glowing and an outer ring that's glowing and those two rings are our material that's being flung out at nearly the speed of light into the outer ring and so that's causing enormous motion so there's an inter and this is has an animation which the Chandra group has actually created for us so the Chandra x-ray telescope has been observing it over many years and actually can see the motion of it so this is just su Ming and because you can just like zoom in you up just like you doing it like you try to look at a picture on your phone or something so just zooming in too so we can see the waves of material moving away from the neutron star and along the jet so material is coming out of that neutron star from the surface of it the equatorial region that where the point where the pulsars magnetic field is approaching the speed of light flings material out at nearly the speed of light and it slams into the materials on the side emitting even huge amounts of x-rays so most of the x-rays on that cloudy structure happened because of electrons and ions that have been accelerated to nearly the speed of light and as they collide with other things they they shock heat the gas to x-rays and emit x-rays the rest of it is due to an extraordinarily powerful magnetic fields that occur in there so the in so there is a huge voltage difference that occurs along that because of the strong magnetic field and that's the thing that accelerates the electrons off of the surface and by excelling that huge voltage difference actually releases an enormous amount of energy as they're pulled off with the surface of conflict the surface of the neutron star because they have to really have to that they have to overcome the pull of gravity so the nuclear magnetic field is creating a voltage difference the voltage difference asked overcomes the pull of gravity and in so doing releases light because that's how it has to that's that's the releasing of energy in that particular fashion so we get these polar Jets that occur that comes from the North and South Poles that are not because of the rotation axis of the magnetic field the magnetic field is making those waves alright so I invite you to go take a look at that that's good because that's really cool because I actually shows movement of something at 6,500 light-years away which is just wild to think and here is a view a more recent image from the Hubble Space Telescope of the Crab Nebula and you can definitely see the Pulsar definitely smack in the center we can see the wispy cloudy structures that occur because of the because of the vast thing that I filled permeating this entire thing and if you got within a Lightyear of that thing it would completely wipe out the hard drive of any computing facility there and if you got within an astronomical unit of it it would tear everything apart because well no it's still a solar mass but if you got within say a couple of radii from it it would definitely rip everything apart there so you don't want to get very close to that because that current that cloudy structure is permeated with a with a stronger magnetic field then can be made on earth and you can still see the the wispy structure of the jet like material that comes out that makes a dusty jet that looks kind of like a dark tendril that points away from the put from the crowd net from the Pulsar and so you've got a bright inner ring that inner ring is where the light is being generated by shock and forming x-rays that x-rays then and this is the Hubble image and visible light the x-rays then step down as they interact with the material in the cloud to make it glow and the magnet and the ions then cruise through these in this very complex magnetic field that permeates the whole thing as the closed Meg as the unclosed magnetic field lines try to recombine even as the shock waves itself push the entire nebula apart so the study of the Crab Nebula is the thing that you do if you want to learn pulsars and neutron stars because is the nearest neutron star that's doing major activity and in fact the Crab Nebula as Messier object number one is an easy-fit target in small telescopes and you can actually see this thing in an 8-inch telescope from a dark location on earth so that's really interesting to think that that's something that happened there can be seen so easily well let's look at other ones so about eleven thousand years ago there was another supernova the Vela that in in the constellation vela exploded and we see that wispy sort of sort of a bubbly structure that's in the middle not the not that bright spherical pink in the up top and not the bright young reddish in the upper left but no the wispy bubbly stuff that looks that kind of looks foamy in the middle and not the blue thing at the top that's just an internal reflection of the telescope from the from the Digital Sky Survey so the that is the super the remnant supernova remnant from the Pulsar that created this thing into the Vela pulsar is part of this and those outer layers crash into the interstellar medium ones and you can see there's a lot of gas and dust in this area and as that material crashes into it it shock heats it and makes it glow so material is just completely completely hitting all of this stuff and it was exploded about eleven thousand years ago and as the material crashes into other stuff it makes a glow and that's where that glow comes from and this image that we see is fans almost about 100 light-years and the object itself is about the diet and this is about 20 times the diameter of the full moon so this is a big big big big composite image from the Digital Sky Survey this is an amazing amazing piece of work by made a video our team at Sky Factory some fantastic piece of work so what's fascinating is is that in my feeling is that eleven thousand years ago was when the first structures were being built on earth in fact the first human structure was gobekli tepe and that was built about 9000 BC which corresponds to roughly when this thing went off and it would have been visible from Turkey where gobekli tepe was it was built so perhaps 11,000 years ago the first people said saw this bright star in the sky and somebody said that's a god and I'm going to make it one so build this big temple so go take a look what that is anyway so the Vela pulsar is something that is actually seen in the sky I when we look at it it's about a thousand it's about a thousand light years away it's nearer than the other it's about it's about twelve miles across so this is actually nearer than the Crab Nebula actually it's a slower rotating pulsar it's about 89 milliseconds but still that thing is rotating faster than a helicopter and there's a jet in the center that's moving about 70 percent the speed of light and we're gonna look at some Chandra x-ray data from the summer of 2011 as it zooms in on the center of the Vela pulsar we see the Chandra data in being in the center so it's going to get rid of the optical view that we see just showing us the Vela pulsar in x-ray light now that Vela pulsar itself is also deeply studied by Chandra so now we're going to zoom in on the central pulsar that created the supernova remnant we saw and that thing actually moves over time so there's a central central central object and there we see the motion of the Vela pulsar we see the Jets moving out at approximately 70 percent the speed of light the pulsar is deep in the center and we see the material rocketing away from the from the disk II the disc that makes it so there's kind of a bent sort of appearance of a disc like structure that's the material coming off of the rotation axis of the Pulsar as it's going at nearly the speed of light and the material just whips away from it and the magnetic field and excites that material to it's shocked and glowing in x-rays but the Jets our material that's going so fast as they slam in the interstellar medium they make x-rays as well as globe I sink relation so that's the interesting thing about the Vela pulsar which isn't a fantastic study and it too is something that is visible very difficult to see in fact it's only visible the Vela pulsar only visible in x-rays however pulsar is in general the crab is one and there's another one called Kamino and cominius primeira Lian x-ray is primarily an x-ray and gamma-ray pulsar but it's very close to the sky to the crab and the Gabino pulsar is a 24 millisecond is a quarter of a second pulsar which is another interesting one they all pulse just like the others and so we also can find that sometimes they come in binaries because remember we talked a while back in a previous lecture that stars come in binaries so sometimes we can get binary neutron stars or neutron stars that are part of a binary system and we can see x-rays that are happening in bursts so then these happen in these instead of pulses bursts of x-rays that happen and then they fade and maybe there's some pulsation that happens because there's neutron star activity like a pulsar and then all of a sudden there's a massive uptick in x-ray in luminosity and that's called an x-ray burst or as part of a binary neutron star set and that would kind of look like this so if you have a neutron star instead of a white dwarf now remember the type 1 supernova was a white dwarf with a companion big star now imagine that it's a neutron star somehow a super a really massive star evolved went supernova its companion maybe receive some of the material or some of it was actually blown apart and accelerated the evolution of it now it becomes a red giant as a becomes a red giant it swells to fill the Roche lobe material falls once it gets close enough to that the gravitational field is greater than the L towards the neutron star than in the center of the other star it falls into a disk there's a hot spot where it contacts that very very very very hot dense disc the disc is highly magnetized of course because it's a neutron star and can bend the path of the can bend the path of the material as it falls in and since the magnetic field of a neutron star is much more powerful than a white dwarf the path of it can then be redirected towards the poles where all of a sudden it does these huge huge huge bursts of energy and once it piles up enough stuff there is massive thermonuclear explosions that can occur on the surface of the neutron star and when they do that we get a burst of x-rays and so we get a binary neutron star making x-ray bursts alright so those two binary neutron stars are where they pulsars are roughly between three hundredths of a second about a third of a second and those are called millisecond but the but a star like we showed can become a millisecond pulsar for like one thousandth of a second and they had to get spun up and so the act of falling onto the neutron star actually imparts the spin of the material orbiting it that then lands on it as it goes around and around and around it spit that spin of the disk and the material then imparts that onto the neutron star and that's called a mill and it can actually make the star go faster and faster so when you have an x-ray burst er you should also have a millisecond pulsar so let's see what that kind of looks like so the donor star has material that's right on top it creates a disc then you get these beam like activities of x-rays happening in these beams now the rotation rate would be a lot faster than that because it's a pulsar right and so the magnetic field redirects the material onto the surface of the neutron star the disc material falls on top of it and as it does so it gets more and more and more massive and the aim the momentum of the disk is imparted to the Pulsar and spins and spins and spins faster and faster spinning it up so that's rather dizzying I hope I'm not triggering anybody with a with any kind of problem so this is what it might look like from above you see the spinning material from from the neutron star going around and around and as it gets closer it spins faster and faster until it gets redirected by the magnetic field to the poles onto the surface of it and then spinning up the neutron star so then what will happen is that after it spins up really fast the material collects on the surface of the neutron star and by collecting on the surface of the neutron star it does an enormous x-ray burst as the light actually as thermonuclear reactions occur but remember that thus the escape speed from the surface of a neutron star can approach the speed of light so these balls of fire this fireball that you just saw at the end can actually accumulate on the surface and oh my gosh I'm actually just not going to show oh I'll skip after this in just a second but that fireball that we saw can actually accumulate on the surface and rotate with it and when that bursts comes along that's what we see as the x-ray bursts because that light from all those except that glows from the expanding hot gas we see it as it glows and it comes into and out of our field of view thus making an x-ray binary all right so binary neutron stars probably are more common because in in globular clusters which is interesting rubber globular clusters are always those old old old stars so there must have been neutron stars formed in the youth of a globular cluster and there must be binaries inside of them so eventually those binaries can be can turn into on total binaries so maybe maybe globular clusters have all these these kind of things in them and they're very dense stellar environments so if there's spun up you might have actually binary stars that might actually collide so x-ray sources probably or millisecond pulsars but you can't get the time resolution and something as distant as a globular cluster in order to know if they actually are millisecond pulsars but to have so many bright x-ray sources in a globular cluster suspect is leads us to the suspicion that they are all right so maybe in that dense stellar environment of a globular cluster two of the neutron stars can get close enough to collide and that is what we can see here is that eventually if they get close enough to collide they would spiral around each other in the center of this globular cluster then the ancient ancient ancient stars as a pair of stars and when they collide they create a new kind of supernova called a kylo nova and a colliding neutron star makes it kill a nova which is an incredibly powerful supernova of two colliding neutron stars alright so we'll watch that video once again because that's kind of cool as they spin spin spin spin spin spin and we actually have seen an observational evidence for such a Killah nova occurring and I'll show you what we mean again by this there's a couple of colliding neutron stars so this is the concept that was done inside of a supernova inside of a collision simulation and we can see that such a collision would take less than a second it would take actually the final throes of it when the two neutron stars start to collide till when they merge into something which is just a mess and since it's an old-new colliding object remember the density that it was this is actually shredding those two things apart which is astonishing that it could actually do that so the combined magnetic field speed rotation orbital rotation and density of these objects mean when they collide they make a really really really really big explosion called a kylo nova and we'll talk about those things when we talk about gravitational waves in the future so what happens when that happens what happens if the remnant of the core is super massive meaning the core of a star is is greater than say about three solar masses if it's bigger than that then the original star must have had a mass greater than eighteen solar masses if that's the case and the star is more massive than about eighteen solar masses then neutron degeneracy which is holding up these holding up these neutron stars and pulsars that will fail and if that fails there's literally no pressure left in the cosmos that can hold the thing up against collapse and the object collapses down to zero radius at infinite density let's let that sit in for just a second that's just an absurdity but there we have it we'll leave you with an absurdity that is a black hole black holes are bizarre bizarre bizarre objects we're gonna complex the the neutron star was well black holes are really simple so it's kind of a weird thing to think that they are that simple so there's some review questions this for your half just so you can have some fun and we'll see you next time

Channel: Jason Kendall

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Rating: 4.7973566 out of 5

Keywords: Astronomy, Astrophysics, Physics, Neutron Stars, pulsars, Jocelyn Bell, Lighthouse Model, Crab pulsar, Crab Nebula, Vela supernova, Binary Neutron Stars, X-ray bursts, Millisecond pulsars, Colliding Neutron Stars, Neutron degeneracy

Id: 2ZDskQI_uIg

Length: 41min 3sec (2463 seconds)

Published: Wed Sep 19 2018