What Is A Nebula?

all right so today i'm going to start the video by showing you some images and i want to see if you can notice a pattern okay okay here's the first one it's the wallpaper i use for my work computer what i edited this video on then there's this one which just so happens to be the wallpaper for my personal computer which is actually what i wrote this video on after that we have this which can you guess is the wallpaper for my phone which in no way helped me make this or any video ever and finally we have this picture which i use for my well let's call it my gaming computer actually that one doesn't really fit the pattern let's just get rid of it okay so just looking at these wallpapers are you picking up on any sort of pattern other than the fact that i might have a few too many computers yep that's right i like space or to be more exact i like pictures of space i don't know what it is about images like this that just captivate me and make me feel like i could stare at them forever somehow they managed to be both abstract but also real lacking any true definition but nonetheless exhibiting shape and form i imagine it's the same thing some people feel when they look at paintings like this or this what this all means is that for the past i don't know 10 15 years i've looked at a picture of a nebula basically every day but my understanding of what i was looking at never really went any deeper than this and well that's just not good enough for someone who self-identifies as atlas pro so today me and you are asking the question what is a nebula the first thing you need to know is that nebulas or nebulae as the astronomy nerds would say don't actually look like they appear in most pictures now i could go into a long explanation as to why this is or i could just point you on over to this vox video which does a better job than i ever could at explaining it yeah you know what i think i will just do that go and watch this video afterwards if you're curious all you need to know for this video is that it's all a matter of light you see space is dark and therefore there are really only two ways of seeing anything either light is emitted from an object like our sun or light is reflected by an object like our moon of all the tangible or baryonic matter in the universe approximately 75 of it is hydrogen and over 24 of it is helium together constituting 99.9 of all things the reason behind the stark abundance of these two elements above all others is rather straightforward being the two most simple elements in existence they were the only substances generated in great quantities by the big bang in the same instant as their creation these elements were scattered across the entirety of space and atom here and atom there free to wander aimlessly through the void on earth if something behaved like this we'd call it a gas and so in space we find what's essentially huge quantities of free-floating interstellar and even intergalactic gas and again just like here on earth most of the time these free-floating gases are too sparse to actually be visible which is why most of space is just a dark nothingness but lucky for us and the whole universe really these gases aren't distributed perfectly evenly this leads some areas of space to contain far more free-floating gases than their surroundings to the point where they can actually interact with light keeping with our earth analogs when enough gas collects itself to be visible well that's what a cloud is and so when this happens in space can you guess we get clouds of hydrogen and helium gas however large opaque gas clouds is only one of two components necessary to make a true nebula like i said a minute ago in order to be visible to us an object must either emit or reflect light and in the vast emptiness that is space most gaseous clouds sit in complete darkness undetectable to us except through computers and sophisticated infrared or uv telescope cameras but as it so happens just like how clouds here on earth can grow to the point where water inside can condense and form droplets if an interstellar gas cloud grows big enough its cumulative gravity can compound some of the gas into a single concentrated point here under the tremendous pressure of a cloud bigger than an entire solar system the very hydrogen atoms that make up the mass can begin to collide and combine in a process known as fusion this process accelerates until part of the cloud collapses in on itself creating a mass of fusing gas held together by the strength of its own gravity a star in this way nebulas can basically be seen as star factories the only place where enough gas can collect in the void of space to produce anything besides helium and maybe some other heavier elements the main byproduct of this is the generation of light and now we're cooking at this point what gas is left encompassing the star has a light source and so a true and visible nebula is born in fact there's not one but two ways a cloud can be made observable the first is by reflecting the visible light that is produced by the stars generated within the nebula these are aptly named reflection nebulae visible light however isn't the only thing emitted from stars and other types of radiation like ultraviolet and infrared can also interact with surrounding cloud particles exciting them to the point where they emit light of their own in the visible spectrum these are emission nebulae together this describes the two means by which a gas cloud can be illuminated though of course it's also entirely possible and actually common for a nebula to both emit and reflect starborn radiation and that's basically all a nebula really is a cloud of gas lit up by the stars harbored therein or at least that's as much as i knew before doing more research for this video as it turns out what i've described so far is only the first of four ways for a nebula to form these are what you would call diffuse nebulas as their creation was the result of the natural and random diffusion of gases throughout the volume of space by far the most common class of nebula these are where all star formation and therefore all other nebula formation originates while there are surely thousands millions even billions of diffuse nebula to talk about perhaps the best example of one comes in the form of ngc 3372 or as her friends call her the karina nebula with a radius of 230 light-years across this is one of the biggest and brightest nebula visible from the earth though don't be fooled no matter how massive it may seem if we zoom out far enough we can see the characteristic gas clouds eventually diffusing away into empty space giving the nebula no strictly defined shape however as time goes on and nebulas precipitate more and more stars each with their own powerful gravitational pulls eventually all the surrounding gases are drawn in draining the nebula and leaving behind clusters of stars without any sort of luminous veil things will stay like this for billions of years as each star lives out its life cycle the length of each star's life depends on its mass but no matter what all stars have limited life spans and it's here at the end of a star's life that a new process of nebulae construction can take place culminating in the emergence of the three remaining classes of nebula the specific type of nebula generated from star death however again depends on its original star's mass if the central star is of intermediate size meaning anywhere between 0.728 solar masses which of course includes our own sun its death will be less of a bang and more of a whimper as the star ages it begins to experience mass loss and not the good kind but rather the kind where an internal battle between the sun's radiation and its gravity causes the star to fling its own flesh out from its body this ejecta forms a new cloud around the dying star one of almost identical composition to the nebula that created it though perhaps with some more helium and oxygen nebulas in this state are referred to as proto-planetary nebulae but for reasons i'll mention a little later this is just a really dumb and confusing and downright nonsensical name so instead i'll be calling them ejected nebulae due to some really complicated astrophysics that i'll be honest i can't even pretend to understand ejected nebulas often take on a two-lobed shape making them really easy to identify though beyond this basic structure the particular nature of their parent stars can propagate some incredibly unique [Music] displays [Music] do [Music] do [Music] however due to the nature of their creation ejected nebulas are the most short-lived of all the nebulous structures as this is not even the final state of dying intermediate stars as a star continues to die its core temperature actually increases until a certain threshold in this case around 30 000 degrees kelvin is reached at which point the star has likely expelled the bulk of its matter and all that remains is the super dense carbon oxygen core a white dwarf the final stage of intermediate mass stars in this state the star emits enough radiation to cause the ionization of surrounding gases turning it back into an emission nebula in doing so this reveals the full scope of the star's ejecta which has usually come to encompass it as a spherical sheath gravity's favorite shape it was this very shape that tricked many early astronomers into thinking that these were planets and hence from the protoplanetary nebula we now have a planetary nebula although if i'm to be honest this name also sucks being based on a misconception and in reality having nothing to do with planets in my opinion a better name would take into account the fact that these are made from stars and would be something along the lines of a stellar nebula or tear me out star death nebula or i don't know if you have any better suggestions leave them in the comments all i know is that it just doesn't make any sense to call these planetary especially now that we know they're completely unrelated to planets that being said if we take a look at a few more examples it'll at least start to make sense how people could have made this mistake before advance to telescopes had come about perhaps the most visually appealing and consequently most popular planetary nebula or i mean stellar nebula is ngc7293 the helix nebula this appearance however is the result of our singular perspective from here on earth and if we take a look around it we'll find a better clue as to the architecture of the nebula featuring a spheric shell as well as an elliptical disk almost giving the nebula's profile the appearance of a planet with a ring system if you didn't know better it'd be easy to confuse the helix with the ring nebula given their similar prismatic cores however back far enough away and the rings of the ring nebula come into the picture representing much thinner clouds produced from the early days of the core star's death just like ejected nebula though based on the special conditions of the central stars stellar nebulas can take on a variety of forms take ngc 6543 the cat's eye nebula where the white dwarf has been encapsulated by a corkscrew-shaped gas cloud which itself is enveloped by a familiar ring the cat's halo another fascinating sight is ngc2392 the eskimo nebula which from our perspective here on earth shows us a dense central cloud surrounded by filaments over a light year in length in my opinion making the nebula look more like a firecracker mid-explosion than an eskimo while it's unknown what exactly has caused these mysterious sparks to form orbiting around the structure at the very least gives us a better idea of what we're actually looking at but okay just for fun let's look at a few more [Music] i find it important to remember that all of these were created by stars approximately the same size as our sun which means at the end of the sun's estimated 12 billion year life span it too will produce a nebula like this in the process not only scattering its body but that of the earth as well and by extension the very atoms that make up your own body across space and so in a way it's all of our destinies to become part of our sun's glowing halo once it dies however the bigger a star gets the more violent its death becomes something like the bigger they are the harder they fall and at around 9 solar masses star death takes on a new form putting on one of the most spectacular displays in the whole universe a supernova while there are a variety of conditions that can trigger a supernova all of which i am not qualified to go into depth about the result is always the same a massive explosion releasing most of the material contained by the star in an extremely brief period of time left behind can either be an incredibly dense neutron star or if the propagator was massive enough even a black hole no matter what though surrounding the final product will be a cloud of erupted material forming what's called a supernova remnant which is finally a name that makes sense in this context due to the violence associated with their creation these can often resemble planetary nebulas in general shape as ejected material expands outward from the star to form a spherical shell but a lot of the time the explosion will also rip the nebulus clouds apart causing them to enter a greater state of disarray [Music] okay so those are the four main types of nebulas we'll encounter in space but that isn't the end of the story you see while nebulas represent places where enough gas has collected to convey the light generated by stars if too much gas accumulates in a small enough area it can have the opposite effect and actually block light from escaping these are known as dark nebulas when they're situated alone in space they look exactly how you'd imagine as dark splotches with barely definable limits only visible by blocking starlight coming from behind but it's important to remember that space is a virtually infinite ether and so the most likely place to find highly concentrated gas clouds is at the center of larger less concentrated clouds a lucky effect of this is that the luminosity of the regular nebula does a better job at revealing what would otherwise be an invisible dark nebula often creating recognizable and even iconic shapes in the clouds perhaps the most well-known dark nebula is the horsehead nebula where a dark cloud protrudes out in front of a greater nebula revealing a roughly head-shaped shadow another extremely popular one is the pillars of creation where it is dark nebulas that form the pillars themselves while being illuminated from behind by the greater eagle nebula ironically because of their more concentrated nature dark nebulae often represents the most active region of star creation within a nebula because of this dark nebulas almost always eventually dissolve into a thinner cloud featuring a cluster of stars at its core we can see this process in action by looking at what i'd like to call the donut nebula where the dark clouds have begun to clear revealing the nebula's bright innards another way of thinking about this is to say that the nebula is eating itself from the inside out there are of course many many many more examples of every type of nebula but as far as answering the question posed at the start of the video i'd say there's nothing left for me to really go over so i think i'll finish this video with a little tidbit of information that i couldn't really fit in anywhere else in the script if this video leaves you wanting to see a nebula for yourself with your own two eyes well maybe you can depending on how dark your night sky is there are a number of nebulas potentially visible from here on earth perhaps the easiest to find is the orion nebula as it represents not only one of the brightest nebulae in our sky but is also featured within one of the most well-known constellations that being yeah orion all you need to do is find orion's belt which is formed by three bright stars all in a row somewhere in the southern half of the sky from here you'll need to find the formation known as orion's sword made from three slightly dimmer stars that hang in a line down from orion's belt except one of these stars the middle one isn't a star at all but is in fact the orion nebula this gives the bright spot a hazy quality that should distinguish it from the more solid sources of starlight around it at over 1300 light years away this represents the nearest site of massive star formation relative to earth helping to explain the nebula's high visibility contained within this colossal cloud is a massive gas over 2 000 times that of our sun resulting in the birth of over 700 stars within and more to come all of that amounts to something you should be able to see yourself so do yourself a favor and try to spot this tonight if you can hi everyone thanks for tuning in if you enjoyed this video and would like to see more space related topics let me know in the comments this video would not have been possible without my patrons as they are what allowed me to invest in this channel and buy the computer necessary to create all the amazing footage of nebulas featured in this video if you'd like to help support me and what i'm doing here there should be a link on screen for my patreon and finally if you want to make sure you catch what video i put out next make sure to subscribe and ok why not hit that notification bell while you're at it thanks

Channel: Atlas Pro

Views: 380,424

Keywords: education, geography, science, atlaspro, space, galaxy, outer, universe, milky, way, sun, star, nebula, cosmos, planet, moon, light, astronomy, orion, constellation, astrology, stellar, earth, helix, ring, alien, telescope, white, dwarf, black, hole, neutron, hydrogen, helium

Id: VFXJnbnN5ro

Length: 20min 14sec (1214 seconds)

Published: Mon Feb 01 2021