tizerist wrote:are the colours of the extra solar planets real?
i thought noone could tell colours of them just yet...
The textures of gas giant planets are based on the paper
Albedo and Reflection Spectra of Extrasolar Giant Planets by Sudarsky, Burrows and Pinto. The paper models the atmospheres of giant planets and divides them into 5 different classes:
I = ammonia clouds (e.g. Jupiter)
II = water clouds
III = cloudless
IV = alkali metal absorption
V = silicate/iron clouds
The paper also includes theoretical spectra for each of these classes, which were integrated by Grant Hutchison to give RGB values used for the planet dots at large distances. The actual textures used may differ somewhat from these colours (at some point I should have a go at fixing this) - this is because of the history of implementing the five-class system in Celestia: I created the textures before I had the integration results. In the cases of classes I to III the textures are OK, but it's fairly obvious that classes IV and V have rather different colours in close-up than at large distances.
I'd be somewhat cautious about the classes as displayed: the algorithm used for assigning these classes doesn't match the results given in that paper (or the follow-up paper
Theoretical Spectra and Atmospheres of Extrasolar Giant Planets by Sudarsky, Burrows and Hudeny). In part, this is because stellar temperatures in Celestia are limited to standard values for each spectral type, internal heating of the planets is not taken into account (e.g. 55 Cnc d would probably be in class II rather than class I as depicted), and also the planet's gravity plays a role (e.g. many of the planets assigned to class IV may have low enough gravity to go up to class V). Also, the algorithm relies on the planet temperature, when to do this properly you have to model the temperature/pressure profile of the planet's atmosphere and see if it intersects the condensation curves of various substances (e.g. ammonia, water, forsterite, etc).