- #1
fbs7
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Pardon the very naive question, but why does the atmosphere in these gas giants seem to have, from a distance, a very clear, sharp and distinctive boundary?
When one looks at Earth's atmosphere from space, it seems to have a fuzzy bluish boundary, gracefully vanishing into the black. I read somewhere that's because the pressure of a gas in a gravity field follows something like
p = po e-kr
There's no sharp boundary in that curve. Now, the same law should apply to a perfect gas in Jupiter, Saturn and in the Sun, leading to a fuzzy boundary; but that's not the case, so something else is obviously at play. The few things I can think of are:
(a) temperature - above a certain point the gases are visible, below that point they are invisible, leading to the apparently sharp boundary
(b) composition - above a certain point the gases have some composition that makes them not visible
(c) telescope sensitivity - that is, if your telescope is sensitive to light at level X, and the level of light reflected by the gases becomes smaller with height, then at certain height the telescope will just not detect light any more, so it's not that the gas ends at certain height, but we're just unable to see gas above a certain height
(d) that law is invalid for high heights in Jupiter, Saturn and the Sun
What is the explanation for the sharpness of the atmosphere boundary in these planets, compared to the fuzzy boundary in the Earth and Mars? Would the same thing apply to say Venus too (although Venus is not a gas giant)?
When one looks at Earth's atmosphere from space, it seems to have a fuzzy bluish boundary, gracefully vanishing into the black. I read somewhere that's because the pressure of a gas in a gravity field follows something like
p = po e-kr
There's no sharp boundary in that curve. Now, the same law should apply to a perfect gas in Jupiter, Saturn and in the Sun, leading to a fuzzy boundary; but that's not the case, so something else is obviously at play. The few things I can think of are:
(a) temperature - above a certain point the gases are visible, below that point they are invisible, leading to the apparently sharp boundary
(b) composition - above a certain point the gases have some composition that makes them not visible
(c) telescope sensitivity - that is, if your telescope is sensitive to light at level X, and the level of light reflected by the gases becomes smaller with height, then at certain height the telescope will just not detect light any more, so it's not that the gas ends at certain height, but we're just unable to see gas above a certain height
(d) that law is invalid for high heights in Jupiter, Saturn and the Sun
What is the explanation for the sharpness of the atmosphere boundary in these planets, compared to the fuzzy boundary in the Earth and Mars? Would the same thing apply to say Venus too (although Venus is not a gas giant)?