Celestia Forums

Hello everyone!

First: No, English is not my native language.

Second: To the question.
For the last years we have been discovering quite many exoplanets (at least a hundred, I guess) but still nobody has really been able to spot the actual planets. Instead they have been found by indirect matemathical methods.

So I was wondering. Wouldn?t it be good to have a of special texture for the Celstia?s exoplanets and unexplored parts of other less known objects? Right now they have almost the same textures as the objects in our own solar-system (the exoplanets looks a bit like Jupiter), and as a beginner its easy to be tricked by that. To think that the extrasolar planets really looks like the textures shows.

Lets say that we instead used an, e.g, black and white checkered pattern (as a chessboard) texture for those "unknown" planets. A texture that would say: "We know that we have an object here but we don?t know anything about its surface".

Just a thought in the dull, rainy afternoon...

// T!

But we do know that they are as big as jupiter more or less, so probably they do look like jupiter, or maybe saturn or uranus or neptune....

Another Guest wrote:Lets say that we instead used an, e.g, black and white checkered pattern (as a chessboard) texture for those "unknown" planets. A texture that would say: "We know that we have an object here but we don?t know anything about its surface".

Ah, Guest, you have wandered out into the minefield! Some of the more lively discussions on this forum have been about how we should show surfaces of objects of which we have limited knowledge. I know many people prefer some cosmetic appearance of detail, even if this is completely imaginary.
But it might be appropriate to use Celestia's "limit-of-knowledge" overlay mask to completely blank out the surface of exoplanets if the user chooses to have LOK switched on.
Any comments on that idea?

Grant

LOK masking sounds quite reasonable to me.

On a more artistic note, however.

There seems to be a progression of coloration in the atmospheres of the solar system's outer gas giants: Jupiter is somewhat reddish with prominant cloud bands, Saturn yellow with less prominant bands, Uranus green and Neptune blue, with progressively less visible banding. To what extent might it be reasonable to portray these trends in the surface textures used for the exoplanets?

A variant colored (for distance from central star as I unterstand selden) lok-masking sounds good to me.

maxim

This brings me a question :

According to physics, chemistry and optics, what kind of realistic color variations can we expect for giant balls of gaz ?

There are, at least, some "parameters" to consider :

-gaz composition
-proximity to the star (temperature effects and star coloration)

Most balls of gaz out there are made of, mostly, hydrogen, helium, methane, ammoniac, carbonic gaz (not sure on this one), nitrogen and maybe water vapor (?).

So I expect a lot of white and yellow. But what else ? Do you think we could see a clear green giant ?

My point of view on this:

Taking our solar system as an example, it seems that the amount of haze near the top of the gas giant's atmosphere increases with distance from the sun, thus the banding on Saturn is less prominent than on Jupiter because Saturn is colder, so more haze is produced. Uranus doesn't have much in the way of visible banding because there's loads of haze.

Going inwards from Jupiter, at some point the planet will get too hot to form water vapour clouds, so the amount of banding might decrease. There have been some suggestions that such gas giants might appear blue because of atmospheric scattering and a suggestion of such a colour was detected from Tau Bootes, but the detection has been disproven.

As for Pegasi-type planets, who knows? While these planets may allow the formation of clouds of metal or vapourised rock, do they contain enough of these substances to form the cloud bands?

As far as I can see, the banding depicted by the textures used on epistellar planets in Celestia fits with the predicted models of atmosphere circulation on such planets, especially the wide equatorial band, so if the image is thought of as a representation of atmosphere circulation rather than visible light, then the texture fits what is known.

maxim wrote:A variant colored (for distance from central star as I unterstand selden) lok-masking sounds good to me.

I'd be reluctant to use colours in the LOK masks - it would imply that we knew something definite about the colour of these bodies. But some systematic variation in the colouring of the default "cosmetic" textures would be easily implemented - I don't know anything about the theoretical basis for this, though.
(For the current set-up I just used the two gas-giant textures that were already present in the Celestia distribution package, choosing the texture with what looked most like fast zonal winds for bodies close enough to be trapped into synchrony.)

Grant

granthutchison wrote:I'd be reluctant to use colours in the LOK masks - it would imply that we knew something definite about the colour of these bodies. But some systematic variation in the colouring of the default "cosmetic" textures would be easily implemented - I don't know anything about the theoretical basis for this, though.

Well I don't know much either. Selden brought up the 'systems planetary rainbow' and it sounds reasonable. If we can set that coloring on the basis of a theory, it would be ok I think. The base color depends on athmospheric main component which itself bases on planets size/density, temperature and distance from main star AFAIK.

And we know something about distance, and density I think. Temperature may be computable.

maxim

And where can you find these epistellar banded textures?Is it party of some download?

daniel,

The ones that already exist are included with Celestia. They're the image files textures\medres\jupiterlike.jpg
textures\medres\venuslike.jpg
and
textures\medres\gasgiant.jpg

There are low resolution versions in \lores\, too.

I think we're discussing the possibility that it might be reasonable to create and use "saturnlike", "uranuslike" and "neptunelike" for some exoplanets.