Celestia Forums

I am planning to create textures for the planets of the 55 Cnc system, with the possibility of an add-on of some kind, and would like to get the textures as realistic as possible.

Some questions about the appearance of b & c: would clouds on these planets be possible?

According to Extrasolar Visions, planet b is too far out for silicate clouds to form, although it does not mention whether other kinds of clouds would be possible (sulphuric acid/sulphur ?  la Venus for example). I suppose long-chained hydrocarbons would also be a possibility, but as far as I have been able to make out these don't occur very much, and on Earth at least they are the products of biological activity. Also, according to this article, epistellar planets may have a layer of broadly-absorbing sodium gas, which would give the planet a dark appearance. However I am not sure what kind of atmospheric temperatures are required to get significant quantities of sodium gas into a planetary atmosphere, or how to work out whether any clouds would be above or below the sodium haze level.

Out of interest, what are the typical temperature ranges for various different cloud types to be possible? E.g. silicates, sulphur/sulphuric acid, water, carbon dioxide, ammonia, methane, nitrogen.

Thanks for any help.

Planet b would most likely be deep blue with very few clouds, as in Extrasolar visions' image of the world, Planet c could possibly have a lot of water ice clouds.

Michael Kilderry

Michael Kilderry wrote:Planet b would most likely be deep blue with very few clouds, as in Extrasolar visions' image of the world, Planet c could possibly have a lot of water ice clouds.

Michael Kilderry

I'm not entirely sure about that. The thing is I don't know what considerations have been made for the Extrasolar Visions speculations. For example I don't think the sodium haze effect has been taken into account on any of the speculations, so I'm still unsure whether there are other cloud types that might be stable in these planets' atmospheres.

Furthermore I am inclined to be suspicious of EV, take the eccentricity of Gliese 777 A b as an example.

Not only that, but Extrasolar Visions seems to have thrown out all of these interesting planet types, but without any documentation as to how he came to conclude what they were. Don't get me wrong, it's a beautiful site; I visit it regularily. But I wouldn't use it as a source of information for planetary appearance or composition, not until there is a lot of reference material added.

I am confused, though; what do you find suspicious about the planetary eccentricity of Gliese 777 Ab?

...John...

Michael Kilderry wrote:Planet b would most likely be deep blue with very few clouds, as in Extrasolar visions' image of the world, Planet c could possibly have a lot of water ice clouds.

Why would it be "most likely" to be blue with few clouds?

Dollan wrote:I am confused, though; what do you find suspicious about the planetary eccentricity of Gliese 777 Ab?

...John...

Both Extrasolar Visions and SolStation give the eccentricity of Gliese 777 Ab as ~0. The Extrasolar Planets Encyclopaedia and the Geneva Observatory and the discovery paper give a high eccentricity around 0.4.

Ah., isn't that interesting. Sol Station is usually much better about such mistakes (and here I am, of course, assuming that the Encyclopaedia and the paper are correct). I wonder if there wasn't an initial change of value that was never reflected on those other two sites.

...John...

Evil Dr Ganymede wrote:

Michael Kilderry wrote:Planet b would most likely be deep blue with very few clouds, as in Extrasolar visions' image of the world, Planet c could possibly have a lot of water ice clouds.

Why would it be "most likely" to be blue with few clouds?

I probaably shouldn't have taken Extrasolar Visions so literally, as a lot of you seem a bit skeptical of the site, and this was one bit of info I got out of the site.

Here's an explanation to b being likely to be blue with few clouds:

Planet b of 55 Cancri is too close to it's star to have water ice clouds, so trhe atmosphere may be nearly cloudless, resulting in Rayleigh Scattering colouring the planet blue.

But then again, the clouds could possibly be sulphur resulting in a giant Venus-like world, or the planet could even have a sodium atmosphere. In other words we really don't know enough yet.

Michael Kilderry

So are there any ways of deducing whether a molecule can remain in the planet's atmosphere over long timescales, and whether it could form clouds?