Hello it's Scott Manley here and today we're looking at Universe Sandbox 2
which is still in early access but is finally available from the developer's
website.
Yeah they've reached alpha 15 and this is a lot of changes in this version I thought
it was time to come back and look at it. They've added music in the background
which is very nice -- it does make it feel a lot more like Space Engine.
You know Space Engine doesn't actually let you do things like, say, explode the
Earth.
There the Earth is now exploded as is Venus and the Sun.
Yes let's explode everything. Actually if I just exploded the Sun unless it exploded
really slowly the mass should still be there.
Well nevermind, look isn't this great? We're starting out a Fourth of July with
with some exploding planets. What else can we do? Can we drop some stuff onto
the planet? That's always fun.
Oh! We have supernovas. We can observe a supernova in the galactic disk. In fact
it
I guess it says Sun nova remnants. That is supposed to be our Sun exploding. We can
watch a supernova in close up in real time although I think we must be wearing
our sunglasses because the star about to go supernova is not that color and it's
temperature is not 0 K
I think they're working on their supernova stellar evolution code. All the
same it's very kind of fun to watch how fast a supernova would explode.
I'm not actually sure if that's how fast would explode but certainly it looks
kind of cool to imagine this thing exploding and laying waste to the
planets nearby
Now I wonder? Oh so they do have supernova type 1A supernova type 1As are really,
really important. So what a supernova 1A is, is a white dwarf suddenly getting
too heavy and turning into a supernova.
Now it's typically a carbon, hydrogen, helium white dwarf if they have things
like oxygen and neon and stuff then they just collapse into a neutron star
instead but there is a magic magic number here and I think this simulation
maybe these are supposed to be Jupiters. They're obviously too small to be Jupiters
but maybe it's supposed to be gas falling onto the surface but clearly
that's not going to work
so with a white dwarf
let's actually just see if I can do this. If I set the mass to .5 notice how
it's much, much bigger.
So we've reduced the mass but the white dwarf has got bigger.
Let's actually make sure we've got this in Sun masses here and as we increase the
mass it gets smaller right. So we're putting more material in the density is
going up and the reason is that white dwarfs are made of something called
degenerate matter what happens with the material is that they get pushed into
quantum states and because of their particle types they can't have
multiple particles occupying the same quantum state and so you get weird
this pressure essential it starts to build up because everything gets pushed
into the lowest energy state and they're stuck there
they can't move so there's this kind of fundamental limit due to electrons
basically and getting pushed around getting pushed into these all quantum
boxes this
it's a little more complicated than that, but this is me trying to explain it in the
using broad simple terms that people can understand. The point is that temperature
normally with a normal gas as you heat a gas up it expands right or the pressure goes
up and it wants to expand and that's how most stars operate as they get hotter
they expand, as they get cooler they contract and this is very important
regulator of hydrogen fusion in the core right. If the core starts to create too
much energy
then the star gets hotter and therefore
the pressure goes up it expands and cools off and hydrogen pressure
the hydrogen fusion goes down.
now in a white dwarf there's no fusion going on. The thing is
entirely being sustained by this electron degeneracy pressure which means
as the temperature goes up it doesn't expand. Now what happens when fusion
starts
occurring again? Well it'll heat up and nearby it the temperature will rise
which will trigger more fusion but the pressure would increase because the
amount by which the pressure increases due to the
temperature increases, is 0.
The only thing holding this up is the electron degeneracy pressure.
So once fusion starts in a white dwarf in the core it will potentially run away
and obliterate the entire star but that only occurs once you reach this
magical mass limit which is about 1.38 1.39? Ok let's see 1.39? We get a
supernova. The entire thing just obliterates itself. The carbon fuses to
oxygen which then fuses to heavier elements. The energy gets trapped, has no
way of escaping until it gets incredibly, super, super hot right.
The temperature rises to like billions of degrees or something? I don't know
like some ridiculous number and at that point suddenly thermal pressure is able to
work again but by that point it is so hot
the fusion reaction has run away. The entire star obliterates itself.
Now how this happens in real life,
how this happens in real life is you might have a larger star nearby. So let's
just try adding a suitable star and I gotta find one that is like an evolved...
Oh Betelgeuse, Betelgeuse. Ok this might not work so well but I'm going to put it
about here
Ok so what would happen is the gravity of this thing would grab the solar wind
coming off of this star and the mass would slowly increase over time.
Betelgeuse is essentially a 15 solar mass star.
Ok this is a really bad example because this star would never be that big.
Normally you're talking, you've got like a 1. you know, 1.3 solar mass star and a 1.1
solar mass star and the heavier one, the 1.3 goes through its evolution
expands and then collapses into a white dwarf and then the other one because
it's lighter it takes longer but when it arrives and it turns into a red giant.
There its companion is nearby able to suck all the matter off eventually it
passes through this magic limit and it goes supernova and we get this crazy
thing.
So you know the funny thing is or the amazing thing is because these type 1A
supernovae happened at the exact same mass, we should actually be able
to do this in the game, let me see if we can do that. I'm going to make the mass
like .8? Yeah .8 on this one
and I'm going to create a second one.
There's Sirius B right there and we're gonna, we're gonna make this one
Sun, Sun, Sun, so we're going to make it .6 right.
So these ones are orbiting and I'm gonna make them collide with each other by
zeroing the velocity so the forces of gravity will pull these two together.
Yeah in theory two white dwarfs if they're orbiting will eventually merge
due to admitting gravitational radiation but generally it's the loose outer
envelope of a red giant star which triggers this. Anyway because the explosion
supernovae always happens at 1.39.
It's always the same brightness and that means that type 1A supernovae are
incredibly useful. You can look at a supernova
look at the color of the light, the spectra and find that it is the type
you're looking for. These things are visible from distant galaxies
so therefore you can use them to find out how far away that galaxy is. It was a
survey of type 1A supernovae which led to the discovery of dark energy, it led
to the discovery that the universe is not only expanding, which we already knew,
but the expansion of the universe is accelerating due to dark energy.
So type 1A supernovae are incredibly, incredibly important and
incredibly violent. You can actually still create a neutron star incidentally by
dropping matter onto a white dwarf but the white dwarf has to have gone
through, it has to kind of be like neon rich or whatever it can't have the carbon
and oxygen because those will explode but the heavier elements it will,
skip through those and just turn into a neutron star.
Is there anything we can bombard the Earth with? Materials? That's always fun.
It is the Fourth of July you know. It'd be kinda nice to have some explosions.
We've already had supernovas. Climate simulation? Galactic collisions yes.
How about that for the Fourth of July? Proper fireworks, eh? Well actually
during galactic collisions, while they may look spectacular,
you get a burst of star formation from the gas clouds that collide but
generally main sequence stars like the Sun. It's unlikely they would actually be
affected in any great way. It's unlikely that they would collide with another
star or have another star come close enough to disrupt the planetary orbits.
No these things would be rather slow affairs. What would happen though is that
after this
collapse and merging, you get a burst of star formation and many of the stars
will be flung off into deep space, where they will end up having a very, very
quiet and cold end of life without any, anyone nearby. They will be lost from
their friends.
Oh look, bombardment of the moon. Here we go.
Chunks of rock falling in?
Here we go. Nice. Celebrate the independence of your planet by blowing
up a chunk of it.
There's one for asteroid day huh?
That was a pretty cool. Universe Sandbox,
you know the orbital mechanics have kind of entered this phase where they've actually turned off
a lot of the features I really like. Their really good integrators,
are currently being rebuilt. Largely because they found performance issues
with things.
I'm told they will come back but the orbital mechanics is kind of taking a
second place the planetary evolution. Look there's so much energy going into
this we've actually had magma and stuff come to the surface.
That's rather beautiful isn't it?
Collapsing moons? Oh the moon's all collapsing in together to create one
larger object. Of course one larger very, very heavy object here.
Nice, nice, nice. Anyway yeah. Universe Sandbox 2.
You can get it from their website, I'll put the link in the description
I'm Scott Manley, fly safe.