LL Pegasi and the mystery of its carbon spiral | Space Is Weird

this thing here I mean it looks like a galaxy right it's like this weird ghostly dusty galaxy but it's not a galaxy it's a star in our own Milky Way there's about 1000 light years away and look lit right that's not a star like what on earth is going on here so if something called ll pegasi or a FGL 3:06 ate any member and it looks like this and i remember the first time that someone showed me this picture and I was like no way that's fake that's not real that's like photoshopped right they're like no no NASA press release this is a real thing that it observed but the Hubble Space Telescope I was gobsmacked like it's really strange so ignore like the bright star in the bull ground because that's just the right star so that's about sort of a couple hundred light years closer to it so this thing is really weird like no question about that against the weirdest thing I've ever seen so what it is is what's called a carbon star so if you take a spectra of the light from that area of the sky you will see there's a lot of absorption from carbon in fact is absorbing all of the light from the star that's in the very center of that spirals but we can't actually see it invisible and so we've seen a lot of these things before across the Milky Way basically they're kind of like the last gasp at the end of a star's life so we're talking about stars that are about the same size of mass is the Sun so huge massive stars that are like 50 to 100 times the mass of the Sun when they get standard of life they have this dramatic explosion that we call a supernova but something like the Sun it kind of goes through this weird period where it sort of tries really hard not to just collapse and die so the way that stars power themselves is through nuclear fusion okay so they take a hydrogen atom it's single acts from hydrogen fuse it together with another atom of hydrogen and you make helium and you need really intense temperatures and pressures to be able to do that so in a scar itself you've got gravity constantly pulling it in and trying to collapse it and then you've got the energy being released from that fusion pushing it outwards all the time but the only place that's actually dense enough or hot enough to be able to get those hydrogen atoms to come together and fuse together is in the very very core of the star so over the millions and billions of years that it lives for you're constantly turning hydrogen into helium but that helium is building up like a waste product and eventually you know you get to the point where in the core you've got no hydrogen left in that area where it's hot enough for dense enough to fuse it together you've actually got no hydrogen left all together then it's not producing any it's not producing energy to stop gravity from collapsing it inwards anymore and so it has this sort of like moment where gravity starts to collapse it but then all of a sudden it's hot enough in a very tight shell around that core to start burning hydrogen into helium again and so what you end up with is this sort of like pulsation where it sort of collapses in and all it's hot enough again for a while until expanding in and then it will collapse inwards again and so you end up would be sort of slowly these building up these shelves of helium further and further out into the star until the point where you then have to start burning helium into the heavier elements like it gets hot enough to do that in those regions and you end up with this sort of onion like structure of more and more elements being made around the core by that way that you're producing so much energy that actually the star swells up to a huge size so this is gonna happen to the Sun and when it swells it's actually gonna go beyond like the orbit and earth you end up with this huge huge star that at the edge it's not really holding on to its gases very well anymore it can start to shed a lot of material as it sort of does this weird pulsing as its producing these shells of material but carbon stars we've seen a lot of them across the Milky Way all the things that are about the times the mass of the Sun which there are a lot of 10/10 their life is carbon stars throwing off material and may sort of shells though so when he's throwing off all this carbon from the star unit blocking the light from the star that you can still reflect other star light off all that gas and dust that the star is thrown off and you end up with what's called like a reflection nebula so we know a lot of different reflection nebulae in our own sky so what we kind of have here with ll pegasi is like a reflection nebula except it's not shells of material like we used to it's this weird spiral so what is going on so actually this spiral structure is actually what's called a perfect Archimedes spiral like literally if you overlay a perfect Archimedes spiral on this thing you'll see that it fits show so well and I said at the beginning you know this thing could kind of look like a galaxy right like a spiral galaxy except your spiral galaxy has what's called a logarithmic spiral so a logarithmic spiral that people will be most familiar you know in nature we see all the times I like shells like hurricanes and cyclones galaxies all logarithmic spirals what happens that if you're gonna draw it the distance between the sort of ever-widening spirals is getting bigger and bigger every time so you're moving around at the same angle but you're actually getting further and further away from every single spiral that you do that's very different to an Archimedes spiral where you're tiling around the same angle all the time but actually what you're doing is you're keeping the exact same separation you're moving away from the center and a constant speed basically and so what you've got here in ll pegasi is clear this case where you've got this material being shared off the central star instead of getting it in shells you're getting it in this sort of constant rate of outflow from the star but like in a spiral shape now back in 99 master Dobis and Morris actually predicted that you would get that pass in if the star that's throwing off all that material wasn't just a single stationary star it was actually in a binary system of star so those two stars and they're going round this sort of center of mass between them you don't have one thing that's going around one star like in a planetary system you know with earth around the Sun you have two stars and they're both orbiting around each other so the star that's giving off all of that carbon material is no longer stationary it's moving kind of like a like a garden a sprinkler system or something right it's like constantly firing it off around the star and then also this one is sort of gravitationally shepherding that material as well into this perfect spiral so that's the hypothesis proving that that is true and it becoming accepted theory is the difficult part so first of all you have got to prove that this thing is a binary star system right and we've already said that we can't see it because all this carbon material is blocking the visible light from the stars but the way that we see through all this dust in the rest of the universe is through infrared light and so back in 2006 when this image was first taken they made sure to check with an infrared telescope this was kept in Hawaii on Mauna Kea and they looked at this star with infrared light and actually found yeah there are two stars there and actually in different infrared photos you see different different stars and so in a red or infrared voting you see like just the one carbon solid it's very red in a middling one you see both of the stars in a very bluish sort of shorter wavelength infrared light you see just the one star that's sort of its companion star okay so that's first drop down proving that it's a binary star okay yes there are two stars that we can see in the center of that spiral so we reckon that around about 40 to 50 percent of stars are actually binary stars like so that means when you look up in the night sky and you can see a single star like and you think that's one strong it's more likely that it's gonna be a binary star because we run about 50 percent in fact one of the stars in the plow or the Big Dipper is actually a binary sorry if you get bananas on it you will be able to see that as well so they're not uncommon things the binary stars so we printed as a binary star there but how do we actually test this hypothesis well under the hypothesis right if you've got these two stars going around each other then the time it takes for them to go around each other should be proportional to time it takes for the spiral pattern to move away so imagine if you're stood in a single place watching these stars go around each other if it takes say 10 minutes them to go around it so it won't but say let's say it does like every 10 minutes you will sort of be hit by a fresh wave of carbon coming off one of the stars right and so that will be the spacing of the spirals so if the spacing of those spirals is proportional to the period of those stars going around each other then we can kind of be sure that it's because of the binary star system that this spiral has been created so you've got to measure both of those things right so this is what the paper in 2006 that first sort of presented this image that have been taken and was like hey look at this little cool weird thing and this is what they tried to do so the easy one there is to measure like the time between those successive spiral turns so because we know how big the whole thing is you can then get an estimate of the distance between each successive spiral turn and then because we know how fast the material is out flowing in the spiral just through you know a taking spectra and getting a redshift we can then work out just from you know time equals distance over speed what is the time do prints between each successive spiral term so this publication from 2006 and they first published this pictures that it was around about 710 years pretty short live national local time skills writers especially when this phase of carbon stars thought to be around about like a hundred thousand years like a million years she's pretty shot so then the next thing you have to do is then figure out if that 710 years coincides with how long it takes for each of those two stars to go around each other what is the orbital period of that binary star system so that's a little bit harder you can get it from sort of the distance they're separated so that image that they took an infrared they can estimate a separation again from knowing how big that appears in the sky knowing how distant they are you can then estimate the actual distance separation of the stars then once you've got that if you make the assumption that both of the stars are the same mass which is quite a generalizing assumption but if you do that you can use Kepler orbital dynamics to be able to get an estimate for the period and so the authors of the study that produced this picture found that that period was around about 810 years divided by the square root of the mass of the star so if each star has mass M it's 800 10 over square root M yes and so if you want to get 710 years which is the spacing between the spiral turns you need a mass of about 1.3 times the mass of the Sun which is kind of the mass you would expect for a common star like it falls in that range so from that result it's becoming quite likely this this hypothesis is true it's not quite accepted there yet because there's still two weird things here about this the first one is why haven't we seen more of these things if 50 percent of stars are in binary systems and you know around about the mass of the Sun stars are pretty common like we should see quite a lot of these things I mean it could just be to do with the fact that the lifetime of a common star is pretty sure in comparison to the lifetime of the main star so when it's happily burning fusion you know the star could live like eight to ten billion years but the carbon staff baby is more of a hundred thousand to a million years so it's not a very large percentage of its lifetime the other thing could also be to do with the fact that you have to see these things like purely face on like with the two stars going around each other like this to get that spiral structure that's kind of all to do with orientation you're not going to see all binary stars perfectly face aren't some of them are going to be moving around this way you know slightly inclined it's all to do with your viewing angle from Earth so combined with the fact that the life time is short and that you have to be at the perfect viewing angle maybe that's why we don't see many of these things the second thing though is that we can even see it it's all like the light from those two stars in the center is completely blocked by all the carbon dust that it's giving off so it looks like that really bright star in the image is what's allowing us to see this thing but actually that star is in the foreground like it's a lot closer to us and a thousand light years away that the spiral is so what light source is actually producing the light so that it's reflected back at us so that we can see this carbon ducts and the authors of the paper that published this image actually suggested that if you look at the direction the light is coming from it turns out that that's where the sort of Galactic plane of the Milky Way is so this thing is actually sort of raised above the main sort of spiral disk of the Milky Way and if you look at the direction of light coming from that disc is in that direction and so what they think it is and the reason that it is so faint is because there's no main star nearby it can light up actually it's being lit up by the entire sort of cumulative star light of the Milky Way it's sort of lit by this sort of galactic glow so it's a privilege we can even see this thing combine the fact that carbon stars have short life times that it's at just the right orientation for us to see this thing and the fact that Hubble can just see it because it's so faint because all it's reflecting is like galactic star light it's incredible it really makes me wonder like what weird wonderful objects do we not know about because we're not in the right place in the universe like to even be able to see them hey curious minds hit my microphone great start X being equal distantly the times the time inconsistent always being okay what is the difference in time between each successive spiral turn turn turn you

Channel: Dr. Becky

Views: 82,900

Rating: 4.960609 out of 5

Keywords: space, #spaceisweird, drbecky, ll pegasi, afgl3068, carbon star, nova, the sun, the death of the sun, carbon spiral, nuclear fusion, star death, physics, astronomy, astrophysics, binary stars, becky smethurst, keck, hubble space telescope, logarithmic spiral, archimedes spiral, spiral, spirals in nature, alma, infrared, space mystery, space mysteries, dr becky, rebecca smethurst

Id: Vx2DFu40MKE

Length: 14min 5sec (845 seconds)

Published: Wed Jan 09 2019