20:11
okay what do we got cold world 2 I thought we talk about today having done cold world one we should move on up the list up the list or down the list so remember these ones are all ordered by how far north they are so cold world one was right up near the pole cold world 2 is still fairly near the pole so I guess we're going down in declination what is cordwell 2 it's a pry one so I have a picture of it here nice looks like biological almost like a cell or something what is it is a planetary nebula so it's one of these things which is the end of a sort of medium mass stars life it's reached the end of its life and it's kind of blown off all the outer layers of the star and so there's just the hot core of the star
left in the middle here at this point in its life cycle it's a thing called a wolf Rea star which is just basically the core of the star that's left over and it's blown all its outer layers in this really rather complicated pattern we think about these things as exploding but it's not clearly just a one of those because there an a massive structure there and in fact if you look carefully maybe you can see there are kind of shell-like structures out here and what that is that as a star gets towards the end of its life it starts kind of pulsating and BEC very unstable and sometimes those pulses become so strong that it ends up throwing off the outer layers of the star and so there's been a
whole series of these and so you're seeing the sort of series of shells that are the sequence of these outer layers of the star being thrown off before the final big explosion of the end so when it throws off an outer layer does it still keep doing the business of being a star or all bets off by this point no it's still it's going through very rapid evolutionary processes so stars go through this process of they start out turning hydrogen into helium then helium into carbon and then on up into slightly heavier elements and as you get towards the end of that life cycle these things happening more and more rapidly and more unstably so it's still sort of burning as a star
but it's just throwing bits off out into space as it does so and what kind of timeline are we talking here is it like 10 minutes and 20 minutes later or 100 years and 100 years later we're probably talking tens of thousands hundreds of thousands of years those kind of time scales so it's still between shell yeah which in you know which in the lifetime of a St you know remember a will sit there for billions of years in it in its sort of earlier phases of life so this is the blink of an eye as far as the star's concerned but it's still like a 100 thousand years it can be tens of thousands hundreds of thousands of years that kind of time scale yeah between these kind of explosions oh I'm I'm
really disappointed like it seems that makes it seem really glacial to me now I know you said why it's quick but yeah you're just you're thinking too much in human terms right you've got to think in Stars terms and as I say in Stars terms this is really quick a lot of the is actually in the complexity of what you can see here so those outer shells which are kind of what happened before the planetary nebula explosion went off but even the this sort of barrel likee structure of the planetary nebula itself the fact it's that shape tells you that there's something you know it's not again not a spherical explosion so there's clearly something going out along the poles of the star and in fact
you can even see jets of material coming out of the poles and in fact there are multiple Jets so clearly there have been multiple events even out there have been going on as well the other thing as well as the faint shells out here I rather like there are actually these sort of radial Rays coming out and what they are is the structure in the middle kind of has holes in it and you're seeing the light from the Star that's shining out through the holes into the space beyond the that Barrel like structure just cuz that's where there are gaps in the barrel where the light's shining out so the star's still going at this point the star I mean you can see the star in the middle it's still shining it's just hot
at this point so it's basically it's reached the end of its life but it hasn't cooled down in sort of about 10,000 years it will cool down and become a white dwarf star and fade away but it's sufficient young now that it's actually still bright enough to be able to see it there is a little bit of a mystery with this particular planetary nebula which is if you look at the star in the middle you can sort of measure it the properties of the light it's giving out the spectrum of the light that it's given out and measure its temperature and it comes out at about 70,000 de Kelvin so very hot structure in the middle but there's another way of measuring the temperature which is that
if you look at the structure around here of course that's all being radiated by that incredibly hot radiation and the effect of that very energetic radiation is that it sort of ionizes the material it rips electrons off the atoms out there and the number of electrons that get ripped off and the different electrons that get ripped off different atoms tell you what the temperature is it's another way of measuring the temperature and that the hotter it is the more ultraviolet light there is the more energetic light there is the more electrons get ripped off so there's another way of measuring the temperature and if you measure the temperature that way you end up with 40,000 de because of
course the light doesn't travel instantly from here to here so it could be that the thing in the middle is varying in its temperature and it just has got hotter in recent times so the lights that reached out to here was from 40,000 de but it since got hotter but it turns out that there's a more likely explanation which is from this paper here called hidden infrared structures in NGC 40 another name for cold world 2 signpost of an ancient Born Again event sounds a bit religious so what they did is they've studied it in the infrared part of the Spectrum in particular the mid and the far infrared part of the spectrum and they'd be able to find that there's another component which you don't see in this Optical
image here which is right down in the middle here there's a little Taurus like structure in the middle a very dense carbon Rich material so stuff basically in the middle there and what's happening is that is acting as kind of a sunblock so that very strong ultraviolet radiation from that Source in the middle is to a significant extent being blocked by the this Taurus of material around it and so actually the temperature of the material the energy of the light that gets through is much reduced from that 70,000 de to a mere 40,000 de it's interesting cuz it kind of resolved the mystery but also it tells you that this thing isn't finished yet in that new structure that structure in the middle is more recent than the stuff out here so there's
clearly even after it threw off all its outer layers there's still more material getting thrown off in these complicated ways in this case of this very kind of soty carbon Rich material in this Taurus likee structure around it what's the end game here you told me the stars going to cool down and become boring what happens to all the stuff at threw off it doesn't go away it's still there but of course there's nothing Illuminating it anymore so you stop seeing it and the reason why you see it is because all that radiation which is ionizing it is also exciting it all and making it AIT light so when that Source in the middle cools down and Fades away then the material around it'll keep expanding slowly into
space but actually you won't see it anymore because there's nothing to light it up anymore there's no planets involved with a planetary nebula there aren't I mean the reason why they're called planetary nebula is cu the first ones that were discovered looked a little like planets cuz they tended to be so quite a few of them were round and clearly extended objects and so they were sort of mistaken a little bit for planets but yeah no planets B why have astronomers who are so eager to reclassify things and ditch Pluto and that sort of thing why haven't they renamed planetary nebula when they when it's such a Mis Noma well we do I mean we hang on to names right for no particular reason and so this is clearly just one of those cases and we do
hold on to the like magnitude scale right we insist on measuring how bright things are using this ridiculous archaic scale which goes about 4,000 years so it's clear sometimes we all just hold on to stuff and planetary neb is quite a nice name so I guess it's probably stuck thanks for watching hopefully you've already watched our previous video about Coldwell 1 and our 110 previous videos about all the messia objects if you'd like to encourage us help us out keep us making videos you can always support us on patreon these names of the people you see on the screen at the moment they're already some of our patreon supporters why don't you join them there's details in the video description in the comments find
out how click on the link join the club thanks everyone
