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beskeptical
2009-May-10, 09:57 PM
The new Hubble image (http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=090510-hubble-nebula-pic-02.jpg&cap=This+Hubble+image+of+planetary+nebula+Kohoutek +4-55+was+taken+by+the+Wide+Field+and+Planetary+Camer a+2+on+May+4,+2009.+The+colors+represent+the+makeu p+of+the+various+emission+clouds+in+the+nebula%3A+ red+represents+nitrogen,+green+represents+hydrogen ,+and+blue+represents+oxygen.+K+4-55+is+nearly+4,600+light-years+away+in+the+constellation+Cygnus.+Credit%3A+ NASA/ESA/JPL) on Space.com of the planetary nebula Kohoutek 4-55 is taken in false colors with blue representing O2. If it weren't for all the other hazards in the nebula, does the picture show a cloud of O2 one could possibly breathe there or is it just a distortion of the image process and the O2 not nearly dense enough to simulate an atmosphere?

Hornblower
2009-May-10, 10:09 PM
First of all, the caption only says oxygen. It does not specify the diatomic molecular version, so we may well have hot, monatomic, possibly ionized oxygen. Even if it is cold molecular oxygen, it will be more rarified than the hardest vacuum we can make in the laboratory, and thus not breathable.

cjameshuff
2009-May-10, 10:49 PM
Remember that the nebula is quite huge. It is a planetary nebula, formed by the explosion of a star, and you are looking through probably about a light year or so of very thin gas. It wouldn't be breathable...if you were there and in any condition to try to make observations, you wouldn't be able to tell there was anything to breathe.

Amber Robot
2009-May-11, 02:17 AM
It's not molecular oxygen O_2 that is being displayed there, it is most likely O II, i.e., once ionized atomic oxygen (O^+). For various chemical reasons, molecular oxygen is very rare in the interstellar medium.

Ken G
2009-May-11, 04:04 AM
Indeed molecular oxygen is generally quite rare everywhere-- to my knowledge, the only really good source of molecular oxygen is the output of photosynthesis! In other words, if we saw a lot of molecular oxygen in an atmosphere of something, we generally wouldn't think "hey, that might be a good environment for life to start", we'd think, "hey, that must be an environment that already has tons of life". I'm probably overgeneralizing, but there you have it.

However, this does raise an interesting question: why is O_2 so rare, and why does photosynthesis make it anyway?

pzkpfw
2009-May-11, 05:18 AM
(
O+ = O+ : sup = superscript
O2 = O2 : sub = subscript
)

beskeptical
2009-May-11, 06:44 AM
OK, I suspected it would be too thin to breathe, molecular structure aside.

So why does oxygen predominate where it does in the image and why is it stratified with the hydrogen and the nitrogen like that?

beskeptical
2009-May-11, 06:46 AM
(
O+ = O+ : sup = superscript
O2 = O2 : sub = subscript
)Too much trouble, unless there is a 'control+[some key]' command. :D I'm already on these forums long enough as it is. But thank you for the offer. At least I don't use text shortcuts. ;)

grant hutchison
2009-May-11, 12:03 PM
OK, I suspected it would be too thin to breathe, molecular structure aside.

So why does oxygen predominate where it does in the image and why is it stratified with the hydrogen and the nitrogen like that?If memory serves, it's not so much the ions that are stratified, but the processes that lead to detectable emission. The central part of the nebula is denser in high-energy photons and electrons, which power the OII and [OIII] emissions.

Edit: Of course, there's also an inner edge to the planetary nebula, a surface directed towards the parent star, which we can see from the outside because we look through thinner layers of gas centrally. We see only sparse emissions from high-energy processes in that central "void".

Grant Hutchison

George
2009-May-11, 04:59 PM
There seems to be a consistency to use green for hydrogen and blue for oxygen (red for sulfur). I would have guessed oxygen, often seen as OIII emissions (500.7nm), would get first dubs on being green and simply assign hydrogen (normally red) as blue. Is hydrogen more important, somehow, and green given the greater priority since our eyes are more sensitive to green?

Nick Theodorakis
2009-May-11, 05:18 PM
...
However, this does raise an interesting question: why is O_2 so rare, and why does photosynthesis make it anyway?

The photosynthetic reaction centers use the energy from light capture to push electrons around. They need something from which to pull the electrons from, and for most photosynthetic organisms, water has proved to be an abundant and available molecule for this purpose; pull a couple electrons from water, and you are left with oxygen and hydrogen ions (and it also turns out they make use of the hydrogen ions as well). In some cases some bacteria derive them from H2S, leaving hydrogen ions and sulfur instead.

Nick

ngc3314
2009-May-12, 02:38 AM
There seems to be a consistency to use green for hydrogen and blue for oxygen (red for sulfur). I would have guessed oxygen, often seen as OIII emissions (500.7nm), would get first dubs on being green and simply assign hydrogen (normally red) as blue. Is hydrogen more important, somehow, and green given the greater priority since our eyes are more sensitive to green?

Well, they didn't ask me. It seems to be a (to my mind, even, rather too pedantic) attempt to maintain the chromatic ordering of filters. [O III] 5007, H-alpha 6563, [S II] 6717+6731 Angstroms. My pleas to at least get [O III] and H-alpha visually right (since they dominate the optical emission of so many nebulae) and fold in [S II] as blue with the excuse that it also has weaker violet lines have usually fallen on hard ground.

George
2009-May-12, 03:56 AM
Well, they didn't ask me. It seems to be a (to my mind, even, rather too pedantic) attempt to maintain the chromatic ordering of filters. [O III] 5007, H-alpha 6563, [S II] 6717+6731 Angstroms. :rolleyes: That's kinda odd considering that it is easier to remember the color of these respective emissions rather than their wavelength.


My pleas to at least get [O III] and H-alpha visually right (since they dominate the optical emission of so many nebulae) and fold in [S II] as blue with the excuse that it also has weaker violet lines have usually fallen on hard ground. Yes, your way is the clear way to do it! Is there no color taxonomy? The black and white age is long dead and vivid colors are here to stay, so we should get the light right :exclaim: Who would you like The Heliochromologist to call, Jeff Hester?? :shifty: ;)

[Added: What's Rio like in August? :) ]

eburacum45
2009-May-12, 09:28 AM
What would this nebula look like to the naked eye from ten light years away, I wonder? A colourless, circular, misty patch, perhaps. Or is the surface brightness bright enough to show colours?

Ken G
2009-May-12, 05:15 PM
I doubt you'd see much-- note that the surface brightness does not increase when you get closer, the nebula just covers more sky. Maybe there are normally unrelved "knots" that might show up brighter if we were closer.

kzb
2009-May-12, 05:32 PM
why is O_2 so rare, and why does photosynthesis make it anyway?

I've often wondered why photosynthesis makes oxygen. Or more specifically, how come nature has evolved a process using virtually the most energy-intensive chemical reaction there is, ie the splitting of the water molecule, to make largely structural material (cellulose).

You would think that dissolving calcium and silicates out of the substrate and using those for structural elements would be much less energy-demanding. Also much more resistant to fire.

Nick Theodorakis
2009-May-12, 05:47 PM
why is O_2 so rare, and why does photosynthesis make it anyway?

I've often wondered why photosynthesis makes oxygen. Or more specifically, how come nature has evolved a process using virtually the most energy-intensive chemical reaction there is, ie the splitting of the water molecule, to make largely structural material (cellulose).
...

OTOH, they are using a nearly inexhaustible (at least from their point of view) power source, and water is so abundant. Early photosynthesizing organisms probably did in fact use other molecules as electron donors (much as purple sulfur bacteria today use sulfides), but the ability to use light, water, and carbon dioxide proved to give them a powerful advantage.

Nick

Argos
2009-May-12, 06:52 PM
Id point out that this very same gas that is essential to life as we know, can also destroy living tissues, for being corrosive. Its one of those great ironies of life.

[Added: What's Rio like in August?]

Can be pleasant. The weather is cooler at the height of the austral winter and skies are very clear [its the dry season].

George
2009-May-12, 09:10 PM
Can be pleasant. The weather is cooler at the height of the austral winter and skies are very clear [its the dry season].Great, I forgot you're already there. Would you mind getting the IAU to incorporate a few minor changes? :)

1) Whereas, stellar remnants formerly known as white dwarfs will be hereby known as either blue subdwarfs, white subdwarfs, or yellow subdwarfs depending on their actual color appearnce, or surface temperature if appearance is indeterminate.

2) Whereas, G class stars, will be considered to be white stars. Those that were called yellow dwarfs, such as the Sun, will now become white dwarfs. This is in accordance with the heliochromological committee and no exceptions to this rule will be allowed. All new textbooks and publications using H-R diagrams or stellar color charts must conform to this advanced scientific revelation. Further, and contrary to prior erroneous standards, at least 2% of all Solar images in any textbook must depict the Sun in its natural color, namely white. Further, kindergartners in science class may not be forbiden to use white crayons when coloring the Sun.

3) Whereas, color assignments for extended objects will conform to the prioritized Keel Classification Code, favoring green for OIII and red for H-alpha.

That should fix things. They managed to tackle Pluto, now on to the more serious stuff.

Bueno Suerte, Argos. Let us know how it goes. :whistle:

Argos
2009-May-12, 09:49 PM
Great, I forgot you're already there. Would you mind getting the IAU to incorporate a few minor changes? :)

I wish I had the power. :) Hey why dont you come down here and defend the propositions yourself, George? They seem great [especially that one about kindergarten kids ;)]

Seriously, Im thinking about attending one or two workshops at the IAU meeting. The problem is that in August Im committed to teaching basic astronomy for kids here in my town, which is celebrating its anniversary as the IAU meeting develops [and will include basic astronomy seminars on the official celebration schedule - the whole month]. Its going to be a busy month.


Bueno Suerte, Argos. Let us know how it goes. :whistle:

Thanks [hey, I like Spanish!]. Ill let you know, for sure. :)

centsworth_II
2009-May-13, 12:07 AM
Id point out that this very same gas that is essential to life as we know, can also destroy living tissues...
Much of microscopic life we know is anaerobic and has no use for oxygen.

George
2009-May-13, 03:51 PM
Seriously, Im thinking about attending one or two workshops at the IAU meeting. The problem is that in August Im committed to teaching basic astronomy for kids here in my town, which is celebrating its anniversary as the IAU meeting develops [and will include basic astronomy seminars on the official celebration schedule - the whole month]. Its going to be a busy month. That is a worthy endeavor.


Thanks [hey, I like Spanish!]. I suspected you would understand it as it is closer to your language than English, and your English is very good. If you can understand me, you are really advanced! :)