the sun has gone through some interesting 
developments. 
We have one last phase and it's the 
pretty one. 
So the sun does get to go out with a 
pretty sight. 
What happens? 
Remember when we stopped we said that the 
thermal pulses were going to eject the 
envelope of the star. 
What we would be left with is the inert. 
Not fusing, no energy source. 
Completely degenerate Carbon Oxygen core. 
This is an object, we'll talk about it, 
it's called a whi, it starts out life as 
what we call a white dwarf. 
It's got about the radius of earth. 
It's got about the mass of the sun. 
It's extraordinarily dense. 
It's extraordinarily hot even though no 
fusion is going on because it just 
stopped being the core of a star that was 
fusing Helium and Hydrogen and so on. 
And was compressed by great masses. 
So this object has temperatures in, of 
many tens of thousands of Kelvin. 
It is surrounded. 
by the atmosphere that it ejected which 
since it was ejected has been moving 
steadily out into space. 
what you have therefore is an expanding 
bubble of gas surrounding an object with 
temperatures in the tens of thousands 
degrees. 
the ultraviolet light produced by this 
exposed core is of course going to ionize 
the gas. 
That's been expelled. 
The ionized gas will then glow in the 
same way the aurora glows and the same 
way that lighting glows. 
And, the resulting objects are some of 
the prettiest in the sky, so we're just 
going to spend a few minutes relaxing, 
and. 
Viewing them because they are pretty. 
They're called planetary nebulae because 
they look round in a small telescope. 
They look somewhat like a gas planet 
would. 
This is the ring nebula. 
We talked about it in our first, 
Video clip and promise to come back and 
explain what this beautiful object is so 
what this beautiful object is, is in the 
middle sits a white world star and these 
are the ejector that they form these 
planetary nebule can be a light year or a 
couple of light years across before the 
material melts into the interstellar 
media taking with it some of the carbon 
and whatever that the star produced 
dredged up and ejected in its solar wind 
so they seed the planetary nebula is the 
stars we have seedingly interstellar 
media with heavier elements 
And we see here oxygen and nitrogen lines 
in the colours, the red is, ionized 
hydrogen, these are the H alpha lines, 
and, 
What we, at some point, people thought 
that this was sort of a slice through a 
spherical bubble of gas. 
It was discovered, upon closer 
examination, that in fact, just like the 
T Tauri Winds, the planetary nebulae, the 
atmosphere of a star gets ejected, but 
not in spherically symmetric way but in a 
biploar flow. 
So this thing has the shape of a 
cylinder. 
The axis of the star's rotation happened 
to have pointed at Earth. 
So we're looking down. 
A tube of the cylinder other nebulee we 
get a different view angle, so we get 
more of a picture of the structure. 
This is the Helux nebula, the cat's eye 
is certainly instructed in telling you 
that there's more structure than just 
spherical. 
There's a lot of interesting questions 
here this one is very nice, its not the 
dumbbell, it's a. 
Another one, but it does show very nicely 
the bipolar nature of the ejecta coming 
out of the store. 
I believe this was a Christmas astronomy 
picture of the day. 
This is one whose intricate structure 
apparently follows from several 
generations of a. 
Ejection of material, in between which 
the axis of the star rotated perhaps 
because a binary partner was influencing 
it or something. 
So that we have ejections in several 
different direction and the combination 
makes for this beautiful shape. 
Conotary nebulus if nothing else, they're 
very interesting but also extraordinary 
pretty and they deserve some aesthetics. 
Before we move on with sun.