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Video transcript
since we've been talking how stars formed and the evolution of stars i thought it was about time that we looked at some cool pictures of stars forming or stars themselves, or evolution of stars. so this right here is from the Eagle Nebula, Just so you know, the word Nebula is kind of a general word for any interstellar cloud of gas or dust so when we're talking about the Eagle nebula, we're actually talking about a huge nebula and actually, it's a nebula that expands. and so that you have a sense, this is just one of the pillars of the "Pillars of creation" This is just a small part of the actual Eagle Nebula And just this pillar right over here, just this pillar here so that you have a sense of how large it is, just this pillar itself is 7 light years it is 7 light years talls so this is an enormous amount of distance remember, the distance from earth to the nearest star was about 4 light years it would take voyager, if it were pointed in the right direction moving at 60 thousand kilometers per hour it would take Voyager 80 thousand years to go 4 light years just this pillar is 7 light years but i wanted to show you this because these type of nebulae, the plural of nebula are where stars can form. so this right here, you actually see, is actually a breeding ground for the birth of new stars this gas is condensing, just like we talked about a couple of videos ago. Until it gets to that critical temperature, the critical density, where you can actually get fusion of hydrogen so this is just a huge interstellar cloud of hydrogen gas and over here you can see its just this breeding ground for stars and we don't even, we think that this structure doesn't even exist anymore because remember, this thing is very very far away from us in fact is, just so you have the number, this thing is 7000 light years away 7000 light years away which means that what we are seeing now, the photons that are reaching our eyes or telescopes right now left this region of space 7000 years ago so we're seeing it as it was 7000 years ago so a lot of this gas, a lot of this hydrogen, may have already condensed into many many more stars so the structure might not be the way it looks right now and actually there was another super nova that happened that might have blown away a lot of this stuff and we won't even be able to see the effects of this super nova for another thousand years but anyway, this is just a pretty amazing photograph in my opinion especially, and its beautiful at any scale and it's even more mindblowing when you think that this is 7, this is a structure that is 7 light years tall and this is really just part of the Eagle Nebula one of the pillars of creation this right here is a star field, and this is as we're looking towards the center of our galaxy the milkyway this is the Sagittarius star field the neat thing here you see is such a diversity in stars this is also kind of mind numbing because every one of these stars, are inside of our galaxy this is looking towards the center of our galaxy this isn't one of those where we're looking beyond our galaxy or looking at clusters of galaxies this is just stars here but the thing here is that you see a huge variety, you see some stars that are shining red, right over here and obviously, the apparent size, you cannot completely tell because the different stars are at different distances and at difference intensities but the redder stars, these are stars in their red giant phase or they're probably at their red giant phase i haven't done specific research on these stars but that's what we suspect those are in their red giant phase the ones that are kind of in the yellowish white part of the spectrum these are stars that are probably in their main sequence probably not too different than own sun the ones that are in the yellowish white, closer to orange-yellowish-white part of the spectrum and the ones that look a little more bluish, or a little bit more greenish these are burning super fast let me see if i can find, this one looks a little big bluish to me, these are burning super super fast, and so the super massive stars, they burn kind of fast and furious and then just die out but the smaller stars, the ones with less mass they burn slower over a much much longer period of time so the ones that are burning fast are emitting a lot of energy at the smaller wavelength part of the light spectrum that's why they look bluer or greener and these are going to be more massive stars the ones that look white or bluer or greener while the redder ones the redder ones are less massive stars that are kind of in their super giant phase and so they are at this point cooler than the main sequence stars this right here, this right here is the cat's eye nebula and the word nebula, this is actually a planetary nebula this one here is a planetary nebula and it's called a nebula because it is kind of this gas that's kinda floating out in space but it's at a completely different kind of scale than this Eagle nebula that we drew over here so when people talk about nebulas, they normally talking about something like the eagle nebula these huge masses of interstellar gas when people talk about planetary nebulas; this is actually still a huge radius but no where near 7 light years but this is the bi-product of a star shedding all of its outer material so at the center of this, we see kind of a mature star here and it's shed of kind of its outer layers and it did that in its red giant phase so the core would keep flaring up, having these hot explosions and every time you have one of these hot explosions, you had more and more of its outer layers getting pushed off, pushed off into space forming this planetary nebula so this as we see it right now its still not yet a white dwarf, it is still an active star fusion is still occurring in this star, but it is well on its way onto becoming a a white dwarf once all its fuel runs out it's past its red giant phase, it's thrown all of this material into space and it's on its way onto becoming a white dwarf anyway hopefully you enjoyed that i actually find all of these images to be pretty captivating especially the star field one because this just inside of our galaxy hopefully it gives more appreciation for how many stars there are i mean this is just a small fraction of the 200 to 400 billion stars inside the milky way