Hi there, today I'm doing a gameplay video and I'm going to be playing the
game Universe Sandbox. I've done a few videos like this on my channel in the
past but it has been a little while since I've done it. The vibe of the video
is going to hopefully be quite relaxing we're going to have a little tour of the
universe and have a look at some stars, things like that, and hopefully you will
learn some things along the way because I'll give you some commentary on the
science that we're talking about and so maybe it'll be a bit of a relaxing
learning session for you. So to start off with I want to open up a simulation of
the nearest and brightest stars. We start off with our Sun in the middle here but
as we zoom out or rotate around we can see all of these nearest and
brightest stars and they've got their labels on them, you can see some of them
around here. So we're just swimming around in the stars at the moment.
Now there's one star in particular that I want to try and find and let's see if we
can get there. The star that I'm trying to find is one of the brightest in the
night sky or at least it usually is. It's usually I think the tenth brightest in
the night sky but you might have heard at the moment it's been in the news that
our good friend over, there I can see him in the background, Betelgeuse or as some
say "Beetle Juice" and perhaps I'll say "Beetle Juice" for the rest of this video.
He has been dimming lately so let's go and visit shall we, let's fly over to the
system here. So Betelgeuse is like I said one of the
brightest stars in the sky usually and it's in the constellation Orion
if you ever see Orion you can see it with your naked eye at night you might
know sort of the shape of the body of Orion and Betelgeuse is right on the
shoulder or actually maybe the armpit as the name Betelgeuse comes from an Arabic
word for the armpit of Orion. You can even see here on this little simulation
that the star is fairly red, it's got this kind of rusty sort of color
compared to you know even the stars in the background, they're a bit more blue
or white even. So yeah a very kind of reddish star and that is something that
you can also kind of observe with your naked eye and a lot of scientists
throughout history have noted that this is a very red star. However back 2,000
years ago Chinese astronomers in their records they spoke about Betelgeuse as
well the same star, they commented on it being a bit of a yellow color and it
seemed to not match up to what we see today. And it actually could make sense
that maybe two thousand years ago this star was in a yellow supergiant phase
and perhaps it has actually gone more red since then. Betelgeuse was created in one of
the stellar nurseries in Orion although it has now been ejected it's kind of a
runaway star off doing its own thing and it is actually traveling really fast so
I think I read this traveling at 30 kilometers per second and it's ejecting
a lot of stellar material gas and that's creating a bow shock around it. It would
have been formed in a place where there was a lot of
interstellar medium, necessary gas and dust and things like that that you need
to create stars and a lot of the other famous stars of Orion would have
probably been created in the same place. So let's get a feel for how big the
star actually is. I'll load up our solar system here we are happily orbiting
around the Sun, Earth there he goes. So what we're going to do is take the
Sun and we're just going to replace it with Betelgeuse I believe that what
I'll need to do is to first delete our Sun. So Sun delete
and while the simulation is paused I will go and find Betelgeuse and put it
in the Suns place. We've got the center lined up there we'll place the star and
I think it's rather evident that we're going to have a problem here.
As you see Betelgeuse is so large that the giant that it is it's completely
encompassing the orbits of Venus, Mercury, Mars, Earth, they're all now within the star.
Looks like Jupiter survived though Jupiter's out here now orbiting around
Betelgeuse. Everything else inside of Jupiter has already been completely
swamped by the star and this would be our new solar system if Betelgeuse was
our star. So we've got Neptune out here, Uranus, Saturn, oh Saturn survived too.
So let's run the simulation and see how the orbits of these planets that remain
would be affected. I can see some little dots in there I guess that is the
asteroid belt. There goes Saturn flying in I can see
some little flare-ups as planets and things
hit the star. Alright so Saturn's gone and Uranus, Neptune all starting to now
change their orbits as we've got this huge new mass in the solar system.
So there we go that gives us a bit of an idea of the size of the star it is about
10 to 20 times the mass of the Sun so that gives you an understanding of
why it's affecting the orbits the way that it is. Let's go and look at some
more stars though not just Betelgeuse, we'll come back to talking about
Betelgeuse in a minute but first let's remind ourselves of you know just
stellar evolution in general and the life cycles of stars. To do that I'm
going to load up a simulation of the nearest 400 stars so here we are these
are our neighbors. This is our stellar neighborhood it's quite beautiful when
you move around and just see that we're really part of this lattice,
really it looks like when you see it like this, of stars and yeah these are
only the nearest ones so there are much more out there that the simulation just
hasn't been able to add. Let's zoom out and see as many as we can. There we go
there's our neighborhood so what I really want to do is create a chart out
of all these stars so let's have a look at our options. I think they are
currently about to arrange themselves by radius and create something that's a bit
nonsensical but what I really want is a chart. Oh we can do an HR diagram so this
is something you see when you're studying astronomy. The HR diagram or the
Hertzsprung-Russell diagram is in every astronomy textbook but we've just
created one here out of our nearest neighborhood of stars
and we can explore it a little bit. This diagram is essentially a plot between
the absolute magnitude of a star, so if we imagine an axis on the y axis which
is increasing in brightness as we get towards the top of the screen and along
the bottom of the screen the axis would be color or effectively the temperature
of the star. If we have blue colors more towards the left those are the hotter
stars higher temperature and more towards the right of the screen we will
have the orange or red stars which are actually a cooler temperature. So see if
we can zoom in a little here we can see that a lot of the stars are along this
kind of central line here going up through the middle on a bit of a
diagonal. Now that is the main sequence so there's all of our stars and there
our Sun will be somewhere in there as well probably about midway up I would say.
That's the main sequence and it's kind of just a tool in astronomy to be
able to classify stars by plotting them on something like this but to also
understand where a star might be in its evolution or in its life cycle.
So most stars would be on the main sequence and stars spend most of their lives on the
main sequence. This is the stage where they are burning fuel they're fusing
hydrogen into helium. Once the star has used up all of its hydrogen fuel it
would exit the main sequence and perhaps come up here like these stars.
These would be our red giants and red supergiants, these stars would be of
reasonably low temperature but very high luminosity so they're very bright stars
and they're nearing the end of their lives. Over here off the main sequence we
have, if we can click on them, some blue giant stars these are young and very hot
stars. There's a bit of a saying in stellar astronomy relating to the lives
of stars essentially it is "live fast and die young"
that kind of refers to these stars here these big stars with a lot of fuel to
burn they will burn that fuel very quickly because they need to because of
their size they need to be burning a lot of fuel to kind of fight against this
gravitational force that's kind of wanting them to collapse in on
themselves so to fight that they need to burn their fuel really quickly. So in a
kind of way that might go against what you'd expect, stars with more mass might
actually live shorter lives and burn that mass up more quickly. The general
life cycle of stars is be born in a stellar nursery, come on to the main
sequence and burn up your fuel then depending on your size perhaps one of
two things will happen to you. If you're an average-sized star you
might burn up all your fuel and then become a red giant expanding in size a
lot and also expelling a lot of your material in a planetary nebula which
will go on to I guess be the material to form new stars. After that your remains
would be a white dwarf maybe a star that would probably be down here on our HR
diagram something that's not very bright but still quite hot. If you are a very
massive star however you might become a red supergiant and instead of just
becoming a white dwarf you might explode into a supernova then becoming either a
black hole or a very dense neutron star. So that's kind of our stellar
evolution we covered there and the reason that I just wanted to talk about
it is because the star of this episode Betelgeuse he's been dimming recently and
we think that might be something to do with him coming towards the end of his
life so we want to understand what the life cycles of stars even are.
I'm back here with our friend Betelgeuse and it's interesting because in October
last year (2019) astronomers noticed that the star was dimming and the dimming
went on for quite a while it's still dimmed now and there's been observations
that it has dimmed by a factor of two and a half times which is I guess quite
a lot for a star although Betelgeuse is a known variable star which means that it's
brightness does fluctuate a bit so a little bit of dimming is actually not
that abnormal although this amount of dimming was quite out of the ordinary so
people were getting excited and thinking does this mean that something
you know big is about to happen maybe Betelgeuse is about to go supernova
maybe this the end of its life. Well why would
dimming indicate that it's about to go supernova anyway? Wouldn't you expect it
to be a lot brighter? Well actually the reason I found for that was that just
before going supernova you know when the star is at the end of
its life it would be ejecting a lot of material and this material might be
getting in between the star and us and absorbing a lot of its light I guess
through extinction of the light and so it's actually appearing dimmer because
of the material that it is throwing off. Of course when it would go supernova
that would be an extremely bright and I don't know spectacular sight for us in
the night sky. It would be as bright as the moon. Everyone has been quite excited
for a while about this because Betelgeuse is expected to go supernova
sometime although the scientific estimates don't say that that will
happen for at least a hundred thousand more years so if it really was about to
happen soon it would be a little early but you know it seems plausible that it
could happen. But a study that was published quite recently February 24th
said that the most likely explanation for the dimming was a large I guess
amount of dust in the way of circumstellar dust which was absorbing
some of the light. So let's see if we can simulate what would happen if Betelgeuse
was to go supernova and I think one of the ways I can do that is open up its
properties and just change our solar mass in here to be 20 times that of the Sun.
oom out a little in anticipation and
see what we get. I toggled the calculated radius on and
off and that has caused us to indeed make this star go supernova. So we can
see this front here expanding out from the remnant it says the Betelgeuse Nova
remnant and yeah that is quite a pretty sight there just watching it expanding out.
So this is what would be a really magnificent sight in our night sky if we
got to see this that's why some astronomers were kind of hopeful in a
way that it would go supernova it would be an amazing thing to be able to study
with the technology that we have now it's not something that we've ever been
able to see that well before or definitely be able to study and in the
kind of ways we would be able to if it happened today.
We've got this red glow really large all the way out here.
Like I said this would be as bright as the moon in our night sky I believe and
would last for a couple of months as it slowly fades away. Betelgeuse although it
is a huge star doesn't have enough mass to become a black hole after this so we
would be left with probably a neutron star at the core there and that would be
I think quite dim so it would disappear from our night sky. I probably wouldn't
hold your breath waiting for this to happen by this stage I think a lot of
astronomers have accepted that maybe we do have to wait the closer to the
expected hundred thousand years for this to happen and maybe some dust just did get
in our way and make it look a bit dimmer and maybe it was also part of it's just
variable life cycle but there's always a chance and if anything the idea that
this could happen or the speculation around it means that you know when you
go outside you might want to just have a little look up at Orion and see if you
can see Orion's shoulder. See if you can see Betelgeuse then see if you think
it's dimming. If you can notice that, that would be a pretty cool thing to see.
If you've got a telescope you might be a bit better placed but even just with
your naked eye as well it might be a really fun way to just engage with astronomy.
So thank you for coming on this little journey through the stars with me today
and I'll see you next time.