welcome back my friends so here we are dressed as a James Bond super villain because I was just
watching some Bill Nye uh and you can't not dress up whilst you watch Bill Nye the guy's got some
serious swag right that's the old term isn't I meant to say grip these days nowadays I might put
the Bill Nye video up tomorrow though and this one tonight and I was already wearing this so
why not you know let's do something different it's kind of funny I enjoy being an idiot so
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we come what is the largest star in the universe and why is it that large and what are me stars
anyway things that would like to be Stars We Begin our journey with Earth not to learn the things
just to get a vague sense of scale the smallest things that have some star-like properties are
large gas giants or sub-brown dwarfs like Jupiter the most massive planet in the solar system 11
times larger and 317 times more massive than Earth and more or less made of the same stuff as our sun
just much much less of it the transition towards Stars begins with brown dwarfs failed stars that
are a huge disappointment to their mums they have between 30. he just said failed stars are a
disappointment to their mothers maybe I'm a brown to all he always wanted me to be a sports star 10
and 90 times the mass of Jupiter so even if we took 90 Jupiters and threw them at each other
although fun to watch it wouldn't be enough to create a star interestingly adding lots of Mass
to a brown dwarf doesn't make it much bigger just its insides denser this increase the pressure in
the core enough to make certain nuclear fusion reactions happen slowly and the object glow a
little so Brown dwarfs are a sort of glowy gas giant that don't fit into any category very well
but we want to talk about stars not failed wannabe Stars so let's move on I've always
just roasting Brown dwarfs at the start of this video so Brown dwarfs form alongside stars and
clusters so there's a lot of studies that suggest there's a huge number of brand dwarfs out there
um the minimum number in the Milky Way is something like 25 billion to 100 billion
but there's probably a lot more than that because uh there's there's many more Brown dwarfs in the
Galaxy that are just too small to be detected with our telescopes currently like hopefully jwste can
help figure this out but yeah main sequence Stars once large gas balls pass a certain Mass threshold
their cores become hotter and dense enough to ignite hydrogen is fused to helium in their cause
releasing tremendous amounts of energy stars that do that are called main sequence Stars the more
massive a main sequence star is the hotter and brighter it burns and the shorter its life is
once the hydrogen burning phase is over Stars grow up to hundreds of thousands of times
their original size but these giant phases only last for a fraction of their lifespan
so we'll be comparing stars at drastically different stages in their lives this doesn't make
them less impressive but maybe it's good to keep in mind that we'll be comparing babies to adults
now back to the beginning the smallest real stars are red dwarfs about 100 times
the mass of Jupiter barely massive enough to fuse hydrogen to helium because they
are not very massive they are small not very hot and shine pretty dimly
they are the only stars in the main sequence that don't grow once they die but sort of fizzle out
red dwarfs our life might have a hard time surviving around a red dwarf and maybe there
was no life found on the planets around a red dwarf very temperamental these small stars and
they have a lot of magnetic activity which results in a lot of flares super flares way more than our
star right and so we thought this would make you know for a very bad situation if the life is on
a planet that has to be closer because they're not as hot right so the planet has to be closer
to sustain liquid water and Life as we know it but recently we figured out that unlike our star red
dwarfs actually seem to flare way more at their poles you know the top and bottom of the star
whereas our star likes to flare around the Equator so we now think of life that you know planets and
life around red dwarfs could actually be you know a good possibility and that Trappist one which
is a famous Red Dwarf system star system and a bunch of planets around this Trappist one star
they could be live and that's like really close to us so who knows one day we might be out of bunny
hop to you know the star system and ah it just gets me going thinking about that I just want
to write a Sci-Fi story about it it's such yeah I'm so upset that you know I won't be around to
seeing that one day but at least some people will be hopefully uh and I'm sure it's going
to be beautiful anyway let's keep going far the most abundant type in the universe because they
burn their fuel very slowly it lasts them up to 10 trillion years a thousand times the current age of
the universe for example one of the closest stars to Earth is a red dwarf star Barnard star but it
so what color do you think a red dwarf actually is so you might be confused to hear that uh red
dwarfs also called M dwarfs are not actually red like what color would they appear well of course
the spectrum is weighted towards a red wavelengths but it has more to do with the physiology of the
eye rather than astrophysics right so it's actually they actually appear like orangish
to be seen without a telescope we made a whole video on red dwarfs if you want to learn more
the next stage are stars like our sun to say the sun dominates the solar system is not doing it
justice since it makes up 99.86 of all its mass it burns far hotter and brighter than red dwarfs
which reduces its lifetime to about 10 billion years the sun is seven times more massive than
Barnard star but that makes it nearly 300 times brighter with twice its surface temperature let's
go bigger small changes in Mass produce enormous changes in a main sequence star's brightness
the brightest star in the night sky Sirius is two solar masses with a radius 1.7 times
that of the Sun but its surface is nearly 10 000 degrees Celsius making it Shine 25 times brighter
burning that heart reduces its total lifespan by four times to 2.5 billion years
Stars close to 10 times the mass of our sun have surface temperatures near 25
000 degrees Celsius beta Centauri contains two of these massive stars each shining with about
twenty thousand times the power of the sun that's a lot of power coming from something
only 13 times larger but they'll only burn for about 20 million years entire generations
of these blue stars die in the time it takes the sun to orbit the Galaxy once
so is this the formula the more massive the larger the star the most by a million years by the way
but once a massive star that we know is r136a1 it has 315 solar masses and is nearly 9 million
times brighter than the sun and yet despite its tremendous mass and power its barely 30
theme song they've got playing in the background to remind him of the uh Armageddon theme times
the size of the sun the star is so extreme and barely held together by gravity that it loses 321
000 billion tons of material through its Stellar Wind every single second
stars of this sort are extremely rare because they break the rules of star formation a tiny bit when
supermassive Stars Are Born they burn extremely hot and bright and this blows away any extra
gas that could make them more massive so the mass limit for such a star is around 150 times the Sun
stars like r136a1 are probably formed through the merger of several high mass stars in dense
star-forming regions and burn their core hydrogen in only a few million people so this means they
are rare and short-lived from here the trick to going bigger isn't adding more mass to make the
biggest stars we have to kill them red giants when main sequence stars begin to exhaust the
hydrogen in their core it contracts making it hotter and denser this leads to hotter and faster
Fusion which pushes Back Against Gravity and makes the outer layers swell in a giant phase
and these stars become truly giant indeed for example gak rocks imagine being told
something as badasses are Dak rocks only to be beat by something called Steve
yeah disappointing only 30 more massive than the sun it has swollen to about 84 times its radius
still when the sun enters the last stage of its life it will swell and become even bigger 200
times its current radius in this Final Phase of its life it will swallow the inner planet
and if you think that's impressive let's finally introduce the largest stars in the universe
hypergiants hypergiants are the giant phase of the most massive stars in the universe they have
an enormous surface area that can radiate an insane amount of light being so large they're
basically blowing themselves apart as gravity at the surface is too weak to hold on to the hot Mass
which is lifted away in powerful Stellar winds pistol star is 25 solar masses but 300 times the
radius of the Sun a blue hypergiant aptly named for its energetic blue Starlight it's hard to
say exactly how long pistol style will live but probably just a few million years even larger than
the blue hypergives are the yellow hypergiants the most well-studded ISRO Cassiopeia a star so bright
it can be seen with the naked eye although it's thousands of light years from Earth at 40 solar
masses this star is around 500 times the radius of the Sun and 500 000 times brighter if the Earth
were as close to Roe Cassiopeia as it is to the sun it would be incited and you would be very dead
yellow hyper Giants are very rare though only 15 are known this means they're likely just a
short-lived intermediate State as a star grows or shrinks between other phases of hypergineness
with red hypergiants we reach the largest Stars known to us probably the largest
Stars even possible so who's the winner of this insane contest well the truth is we don't know
red hypergiants are extremely bright and far away which means that even tiny uncertainties in our
measurements can give us a huge margin of error for their size wore still red hypergiants are
solar system-sized behemoths that are blowing themselves apart which makes them harder to
measure as we do more science and our instruments improve whatever the largest star is will change
the star that is currently thought to be among the largest we found is Stevenson 218. it was
probably born as a main sequence star a few tens of times the mass of the Sun and has
just named that after himself likely lost about half its mass by now whenever you're
feeling stressed just remember that the largest star in the universe is named Steve and even he
has trouble keeping himself together gotta love that one of the biggest objects we've observed
in the universe is called Steve while typical red hypergiants are 1 500 times the size of the
sun the largest rough estimate places Stevenson 218 at 2150 solar radii and Shining with almost
half a million times the power of the Sun by comparison the sun seems like a grain of dust
our brains don't really have a way of grasping this kind of scale even at light speed it would
take you 8.7 hours to travel around it once the fastest plane on Earth would take around 500 years
dropped on the sun it would fill Saturn to orbit as it evolves it will probably shed even more mass
and shrink down into another hotter hypergine phase accumulate heavy elements in its core
before finally exploding in a core collapse Supernova giving its gas back to the Galaxy
this gas will then go on to form another generation of stars of all sizes
starting the cycle of birth and death again to light up our universe let's make this journey
again but this time without the talking the universe is Big there are many large things in it
all right let's talk about some theoretical types of stars which actually might be able to challenge
a big old Steve for our largest star in the universe but just please keep in mind completely
theoretical they probably don't even exist right so let's start with dark matter stars but these
things would have existed before the first normal stars were born right but if they're real they
could exist today so you might be confused by the name because these aerial Stars would actually
mostly be made of normal matter which like hydrogen and helium like our sun right but these
dark stars would also have significant amounts of this stuff called neutrolino dark matter
so in the same way that atoms make up normal matter these neutrally nose are a hypothetical
type of particle which some physicists think might make up dark matter and some supersymmetry
theories suggests these neutrolenos might even be wimps which are weakly interacting massive
particles a common Dark Matter candidate right if these theories are correct these neutrally no
particles actually serve as their own antimatter which means if they ever touch each other they'll
completely annihilate which would generate a lot of energy in the heat right and the raw power of
this Annihilation would actually allow Dark Matter stars to continue like going for billions of years
without ever needing to collapse to undergo nuclear fusion which is like a prerequisite
to normal Stars right so this means these things could be huge like growing to tens or
maybe even like thousands of astronomical units in diameter which is the average Earth Sun distance
so even though they're this big their lack of fusion relatively low temperature would
probably make these things like truly tough maybe even invisible to our eye so but before you get
too excited about stars made of dark matter you should probably know that experiments in particle
colliders haven't even been able to turn up any convincing evidence in neutral Enos all right
let's talk about these quasi-starters to wrap up so Steve you know had a the largest style we've
ever seen right had a radii of like 2150 times out of our sun these quasi-stars you're talking like 7
000 times larger than the Sun and the diameter can be like well into the billions that's like
the largest are thought to be like six billion miles of like hot you know fuming Gas and energy
but the main difference between normal stars and these quasi-stars isn't actually in size it's
in the process at the course so an average style will use Fusion as its energy source as I'm sure
you know right but these glazostars they take a a more extreme route they actually have black holes
at their core and these things would be feeding on incoming matter and this would give off radiation
that would power the star right and so these things would grow rapidly and balloon to like
thousands of times the mass of the Sun so the idea is that eventually they become supermassive black
holes with billions of solar matters you know at the center of most galaxies in the universe
um supermassive black holes are like kind of a mystery they're everywhere uh and there's
ultramaster black holes as well like they're really big ones we can't really explain uh how
they got so big so quickly so this quasi-style route is kind of like a theoretical solution um
but we really don't know I think we'll wrap it up there guys hope you enjoyed watching just remember
those stars that we just talked about they're theoretical uh and I'll catch you next time