Is the RING NEBULA actually a bubble, or is it a cylinder?

Question

Is the RING NEBULA actually a bubble, or is it a cylinder?

Answer 1

It was always though of as a bubble before, but the latest thinking is that it is a cylinder that we see end on. That just seemed so unlikely that nobody ever considered it before. I don't know exactly which opservations have led to the new thinking, but I am sure it as to do with the newer, bigger telescopes.

Answer 2

Actually its neither.

It is true that we used to think that this and many other planetary nebula were "limb-brightened bubbles".

Now it looks like most planetary nebulae are rings (more like a donut than a cylinder).

But even this isn't settled. Using observations of molecules, we can use the Doppler effect and determine how the gas is moving which helps to build a 3-D picture. The Ring Nebula looks like it might be (American) football or Rugby ball shaped and limb brightened.

And this is embedded in something larger and fainter that is more spherical.

Also - if you search for infrared images (e.g. from Spitzer), in molecular hydrogen, the Ring Nebula is much bigger and looks like a flower.

ADDED:

here's the Spitzer Space telescope image:

http://www.spitzer.caltech.edu/Media/rel...

and here's the Wikipedia entry that talks about shape - it seems to be remarkably up to date (describes it as a prolate spheroid = football)

http://en.wikipedia.org/wiki/Ring_Nebula...

Answer 3

http://antwrp.gsfc.nasa.gov/apod/ap06062...

Here is NASA APOD shot of it.  The hubble telescope revealed that it is a cylinder.  Read the caption here.  This is one of my favorites!  

Answer 4

most planetary nebula are kinda like two bubbles next to each other that "touch" in a ring.  I believe this is due to the spin of the star before it went nova.  look at a number of other planetary nebulae and you should get the idea.  

Answer 5

It's a hollow sphere, but the gas is so diffuse that we can only see it at the "edges" where we're looking through the greatest "thickness" of the gas, from our point of view.

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