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Thread: How much water is on the Sun?

  1. #1
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    How much water is on the Sun?

    Scientists have found steam on the cooler sunspots. So given how big the Sun is, how much water are we talking about here? Gallons? Swimming pools? Earth masses?
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  2. #2
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    Water is one of the most common molecules in the universe. It would be surprising if the sun were not loaded with it.

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    At the surface temperature of the sun, the vast majority of the water molecules will have been dissociated by the heat. Even in cooler sunspots, most will still be dissociated. There's enough to be detected, so it's not a trivial amount, but I'd be surprise if it's even enough to fill a swimming pool.

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    I'd hazard a guess that it is a lot, more than a swimming pool.

    The sun is 330,000 times the mass of the Earth and the first 10 things on the sun (Hydrogen, Helium, Oxygen, Carbon, Iron, Neon, Nitrogen, Silicon, Magnesium, Sulfur) make up make up 99.96 of it's mass. That leaves .04% or 132 earth masses of stuff to play with. Water probably isn't in the next materials found on the sun, but following that pattern, your still looking at .05 of the Earth's mass. If you follow that pattern again, it comes out to be 1/20000 of one Earth. That a lot of material.
    Solfe

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    Quote Originally Posted by Solfe View Post
    I'd hazard a guess that it is a lot, more than a swimming pool. ...
    I'm not sure I followed your logic. Water dissociates into Hydrogen and Oxygen at about 3000K. The surface of the Sun is a good bit warmer than that. Any water you see on the Sun would have to either be in a cooler place, where it forms, and then dissociates again, or perhaps there is some magnetic way to protect it that I'm so far unaware of... so Sunspots. When there are sunspots, there is a chance for some water/steam to form. Swimming pools of it? Not sure, but probably not much more in any case. When there are no sunspots, no water at all.
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    Quote Originally Posted by antoniseb View Post
    I'm not sure I followed your logic. Water dissociates into Hydrogen and Oxygen at about 3000K. The surface of the Sun is a good bit warmer than that. Any water you see on the Sun would have to either be in a cooler place, where it forms, and then dissociates again, or perhaps there is some magnetic way to protect it that I'm so far unaware of... so Sunspots. When there are sunspots, there is a chance for some water/steam to form. Swimming pools of it? Not sure, but probably not much more in any case. When there are no sunspots, no water at all.
    I didn't think of it that way, that it is forming from dissociated H and O in very specific spaces. It sounds to me that any area that is cool enough to have water, can have water. Some of those sun spots are as big around as the whole Earth. That's a lot of area to possibly have water.

    Either A) there is a lot of water by mass in those sunspots or B) we are ridiculously good at detecting even very small of molecules. Now that I am more awake, I am not sure which is more likely. We are very good at detecting things, so maybe that one is a better answer. I still think a half million litres of water is a very tiny amount relative to the size of the sun or even just one sunspot.

    It would be interesting to know what shape these clouds of water vapor have. I don't know if that is actually knowable. I imagine that they look like an aurora. A dense layer smeared upwards. What makes me really scratch my head is, does a layer of water vapor have a natural barrier to formation on top of it? Perhaps where the pressure is too low, speeds too fast to let O and H stick together and water formation stops? Imagine a fountain of water vapor. Pretty picture, but perhaps not accurate at all.
    Solfe

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    Quote Originally Posted by Solfe View Post
    I didn't think of it that way, that it is forming from dissociated H and O in very specific spaces. It sounds to me that any area that is cool enough to have water, can have water.
    IIRC, sunspots are around 4000K. The photosphere varies from 6390K to 5000K, the latter is the top of this region.

    Assuming something like the mag field, as was suggested — and are highly concentrated at sunspots — gives single water molecule formation a fighting chance, then wouldn’t they soon disassociate as the get carried upward into the much hotter regions? The spectral line strengths for these single molecules should reveal their quantity, I’d bet. Clouds are hard to imagine in this environment.
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    If the notional "dissociation temperature" of 3000 K is temperature at which steam is 50 % water molecules, 50 % hydrogen and oxygen, what is the temperature at which steam is for example 0,5 % water molecules and 99,5 % hydrogen and oxygen?

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    Quote Originally Posted by chornedsnorkack View Post
    If the notional "dissociation temperature" of 3000 K is temperature at which steam is 50 % water molecules, 50 % hydrogen and oxygen, what is the temperature at which steam is for example 0,5 % water molecules and 99,5 % hydrogen and oxygen?
    I would think that UV light would be more significant factor than temperature turning water into 'swimming pools' of Hydroxyl.

    The Hydroxyl would be nearly as dangerous to a person as the rest of local environment.
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    Water on the Sun yields more secrets to spectroscopy (Tennyson, Polyansky 1998)
    Accessed at: http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

    This has a nice (if dated) summary of the issues they hit assigning quantities to the water features observed. It looks like, from a quick literature review, that the uncertainties due to the questions about transition probabilities are still pretty high so a firm estimate of the amount of water there is not going to be very accurate.

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    The solar photosphere has a density of 10^-9 g/cm^3 or less. At its densest (and not all of it is that dense), that's 6 magnitudes less dense than the Earth's atmosphere and 9 magnitudes less dense than that pool of water. So while the area of a sunspot is large, there's really not much matter there at all. So take that into account when you try to estimate how much water is in one of them.

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