Big Saturn
Feb. 26th, 2005 02:26 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
mmcirvinBy the way, if you want a desktop picture of Saturn, this will probably do the job no matter how big your monitor is.
Another note on color expectations: For a long time I thought JPL was exaggerating the blueness in pictures of the ring-shadowed region near the terminator in the northern hemisphere of Saturn; it didn't match old Voyager pictures. I even toned down the blueness in my own color composites.
But the current story is that the pictures really are that blue. It's probably a combination of several things. The blue color here comes from Rayleigh scattering of light by gas, just as it does on Earth. The dominant golden color, on the other hand, comes from the yellow tint of Saturn's clouds. Near the edge of Saturn's disc, we're looking through the atmosphere at a glancing angle and Rayleigh scattering becomes more important; near the terminator, the incoming light is doing the same, with a similar effect.
Finally, the Voyagers encountered Saturn nearer the Saturnian equinox; there may be a seasonal effect in which the yellow clouds sink deeper into the atmosphere in the winter. Pictures taken from Earth, with Hubble and other telescopes, do show blueness around the edges of the disc, but it's hard to see the winter hemisphere well from Earth because the rings get in the way.
Another note on color expectations: For a long time I thought JPL was exaggerating the blueness in pictures of the ring-shadowed region near the terminator in the northern hemisphere of Saturn; it didn't match old Voyager pictures. I even toned down the blueness in my own color composites.
But the current story is that the pictures really are that blue. It's probably a combination of several things. The blue color here comes from Rayleigh scattering of light by gas, just as it does on Earth. The dominant golden color, on the other hand, comes from the yellow tint of Saturn's clouds. Near the edge of Saturn's disc, we're looking through the atmosphere at a glancing angle and Rayleigh scattering becomes more important; near the terminator, the incoming light is doing the same, with a similar effect.
Finally, the Voyagers encountered Saturn nearer the Saturnian equinox; there may be a seasonal effect in which the yellow clouds sink deeper into the atmosphere in the winter. Pictures taken from Earth, with Hubble and other telescopes, do show blueness around the edges of the disc, but it's hard to see the winter hemisphere well from Earth because the rings get in the way.
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Date: 2005-02-26 11:39 am (UTC)more thoughts on the terminator
Date: 2005-02-27 09:46 am (UTC)Also, when looking from the vicinity of the Sun (places such as Earth), the limb of the planet is darkened somewhat because it's both the horizon and the terminator, which makes it harder to see the blue of Rayleigh scattering around the edges.