A Specter In The Eastern Veil (APOD 2008 Nov 01)

[orin stepanek]

http://apod.nasa.gov/apod/ap081101.html

An Awesome view! 8) With all the hydrogen and oxygen in this nebula; could there be a large amount of ice being formed there? Or having been formed there when things were hotter?

Orin

[Chris Peterson]

An Awesome view! 8) With all the hydrogen and oxygen in this nebula; could there be a large amount of ice being formed there? Or having been formed there when things were hotter?

Ice in bulk tends to not be very stable in an environment like that. I expect that any ice which survived the parent supernova was sublimated away in short order as surfaces were bombarded by high energy particles.

While there is a lot of H and O in an absolute sense, the density is still very low. The brightest parts of that nebula would qualify as a hard vacuum by most definitions. So I expect the sort of chemistry that takes place is unusual. No doubt, water molecules must be created and destroyed, but I don't know whether the creation rate or the dissociation rate is higher. Water is often seen (spectroscopically) in nebulas, but I don't know if it has been detected in this one.

[orin stepanek]

Thanks Chris! Just out of curiosity what would it take? Perhaps a star forming in the region? Do the hydrogen and oxygen atoms just float around at random until some catalytic event happens? I'm sure the conditions would have to be just right + I imagine the concentration levels would also have to be up.

Orin

[Wadsworth]

As in, what is the level of pressure necessary to keep water molecules together..? Here is a nice little presentation on vapor pressure.

Put some water in a vacuum and it 'boils' (dissosiates) into individual atoms.

[Chris Peterson]

Thanks Chris! Just out of curiosity what would it take? Perhaps a star forming in the region? Do the hydrogen and oxygen atoms just float around at random until some catalytic event happens? :? I'm sure the conditions would have to be just right + I imagine the concentration levels would also have to be up. :?

Since this is a supernova remnant, the material is getting less dense. Probably not the sort of conditions where bulk material forms at all, and anything volatile will evaporate, if it hasn't already. Note that water molecules are not volatile, and there is no reason that they won't form as the result of collisional processes in a region containing both H and O. But they can be dissociated back into H and O when they absorb a high energy particle.

In order for bulk material to form (including ice) I'd expect you'd need a gravitationally dense region, such as a developing star system, where material densities are high enough that you get actual clumping.

[Chris Peterson]

As in, what is the level of pressure necessary to keep water molecules together..?

Water molecules are stable in a perfect vacuum. The molecules won't come apart until you reach near ionizing temperatures.

Put some water in a vacuum and it 'boils' (dissosiates) into individual atoms.

Close. If you put bulk water into a vacuum (depending on temperature) it evaporates or sublimates into individual water molecules. These molecules do not dissociate into their constituent atoms in the absence of an external energy source that can break the atomic bonds.

[orin stepanek]

http://apod.nasa.gov/apod/ap081101.html

Is it me or do the hydrogen and oxygen bands appear to be electrical in nature? It may be just an illusion; but it looks very similar to lightning. While I don't believe an electrical charge could be or last that long; the appearance is very intriguing. 8)

Orin

[Chris Peterson]

Is it me or do the hydrogen and oxygen bands appear to be electrical in nature? It may be just an illusion; but it looks very similar to lightning.

I don't see that. It looks like shock fronts in gas to me- lacking the fractal appearance of lightning.

[starnut]

http://apod.nasa.gov/apod/ap081101.html

Is it me or do the hydrogen and oxygen bands appear to be electrical in nature? It may be just an illusion; but it looks very similar to lightning. While I don't believe an electrical charge could be or last that long; the appearance is very intriguing. 8)

Orin

Would a lightning or any electrical discharge be visible in the vacuum/near-vacuum of space? Across several light years between start and end points? I would doubt it.

Gary

[Chris Peterson]

Would a lightning or any electrical discharge be visible in the vacuum/near-vacuum of space? Across several light years between start and end points? I would doubt it.

No, certainly not. And if the medium was dense enough to support them, we'd see an entirely different sort of spectrum. I'm sure Orin was just commenting on the visual effect, not suggesting this was any sort of electrical discharge.

[orin stepanek]

Would a lightning or any electrical discharge be visible in the vacuum/near-vacuum of space? Across several light years between start and end points? I would doubt it.

No, certainly not. And if the medium was dense enough to support them, we'd see an entirely different sort of spectrum. I'm sure Orin was just commenting on the visual effect, not suggesting this was any sort of electrical discharge.

True Chris: BTW, I think the visual effect is Awesome. The greens and reds given off by the hydrogen and oxygen make a spectacular showing. 8) Orin