WR 140

[Tom C]

So, what this looks like is gas being emitted from the equator of WR 140, and it is pulsing. The planet may be “coming apart” around its equator and then going back together. The gas is emitted, then it is stopped, then it is emitted.

 

[billslugg]

It is a Wolf-Rayet star, nearing the end of its life, used up most of its hydrogen, now fusing the heavier elements. It shrinks down, heats up, gets energized and expands, blowing off a layer. Cools down, shrinks and repeats.

 

[Tom C]

Great analysis. I have one question. Why is the material only blowing away from one plane, such as an equator? Why doesn’t it blow off evenly from all over the star?

 

[billslugg]

It blows off evenly, we see the rings as that portion of the spherical shell which happens to be edge on. There is some asymmetry in velocity which is what causes the "box" effect.

 

[Tom C]

I'm still having trouble with only being able to see the portion of the shell that is "edge on." Why can't we see the rest of the sphere. Wouldn't it just look like a giant ball?

 

[Unclear Engineer]

A nice discussion of this star is here: https://en.wikipedia.org/wiki/WR_140 .

But, I am wondering why it says that the star is only fusing helium in a cyclical manner, but it is blowing off silicon, carbon, oxygen, etc. from its outer layers. Aren't those elements a step beyond helium fusion? And, wouldn't they be deep in the core of the star?

 

[billslugg]

I'm still having trouble with only being able to see the portion of the shell that is "edge on." Why can't we see the rest of the sphere. Wouldn't it just look like a giant ball?

Each spherical shell is too thin to be seen face on. It is only when looking at the edges that our line of sight passes through enough of the shell to make it visible. This is known as the Limb Effect and is why the Sun looks darker at the edges.

 

[Tom C]

Ok—I understand now.

 

[Phillip Huggan]

The rings are brighter at bottom left and appears to be top left. It could be space dust but more likely is a velocity assymettry from the star. A wobble in its rotation might synch up its magnetic fields in a periodic sin wave every few rotations, like a pole reversal on Earth.