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.
