[BlueAngel]

I am attempting to get a few things accurate in terms of planetary properties. I'm currently just writing the bare bones of the story, and planning for future details. I won't be going into deep detail of the sciences of it, since the story is told from the POV of an alien coming of age during a time of struggle.

It's theorized that plant-life on other planets may be either blue, red, or black. I picked this info up here http://io9.com/386310/alien-plants-of-many-colors
This world orbits a Class G star, similar to our sun, but not quite the same intensity I think. Plant-life is going to be varying shades of red in order to best absorb this star's light intensity.

I'm not going to be very detailed in my writing about the atmospheric makeup or gravity, but if anyone thinks it may help with some other areas feel free to suggest.

Now what I'm trying to figure is how the light of this particular sun might look on another planet. What color? What intensity? Might this also affect the pigmentation of the planet's fauna?

Any help is greatly appreciated. :) ~Angela

[kmtolan]

I say pick a color you like.

1. Gas or material in space can change a star's color.
2. The type of star can change its color from blue all the way to red (just watch the physical properties of that particular life cycle).
3. Any sort of particulate in the atmosphere can render color changes.
4. The atmosphere's composition can change color.
5. <insert imagination here>

Kerry

[Aether Monkey]

Make me believe.

That's the little phrase that goes through my mind when wrestling with technicalities. Mostly what people want is the spell to be engrossing, unbroken, and memorable.

So that is the rule of thumb I use. There will always be those who will argue details; I try not to get bogged down too much with satisfying them. On the other hand, rich detail (subtly phrased) really helps to bring something to life.

Ultimately, I think credibility has a lot to do with how the story is told.

[mylinar]

Readers can be different. AM and I both like it to be realistic. But I think, you make the planet seem absolutely spectacular, and your writing is strong enough to do so, then many readers won't care to much about whether or not it's possible to be the color you chose. They will simply be engrossed in it.


I think Robert Silverberg's Majiipoor is a great example of this. The world seems somewhat implausible given its vast size and so forth. However the world he created is so spectacular that these issues are easily ignored.

[Fung Koo]

Now what I'm trying to figure is how the light of this particular sun might look on another planet.

Well, this is where the stuff about atmosphere becomes relevant. All stars emit light across all wavelengths (in effect), and so from space their light will always appear white (white is kind of a misnomer, but you know what I mean -- full spectrum). It is only when light is filtered through a medium that we perceive differences in colour.

So, when you look at the night sky and see different coloured stars, what's happening is that white light is being filtered through our atmosphere and revealing dominant spectra within a star's emitted light (those dominances being determined by the star's size, age, and specific atomic make-up). But, that same star will look different again through a different medium.

Our atmosphere is mostly nitrogen (78%ish), oxygen (21%ish), with the remainder being mostly argon gas, water vapour, and dust. The colour of our sun is a product of the atmosphere through which it is viewed, same as all other stars.

At midday, the sun looks pretty much white. The sky, meanwhile, is blue because the composition of our atmosphere tends to absorb and re-emit light within the blue spectrum. It propagates this colour much like a gain medium in a laser, but without the coherence effect -- blue light is absorbed by gas atoms, then kicked back out at the same wavelength at which it was absorbed, reabsorbed and kicked back out, over and over and blue all the while. The other colours mostly pass straight through the atmosphere unabsorbed, but blue/indigo light from the sun itself (high frequency wavelengths) tends to get scattered by the dust and particles in the atmosphere, making the remaining light appear yellow. Those wavelengths are dominant in the light emitted by our sun.

(Scattering, PS, is why we have twilight -- the atmosphere continues to propagate blue light outward, beyond the solar horizon. In effect, the air is glowing.)

So, the color of the star that will be the sun for your alien planet will be the exact same -- its colour will be determined by the atmosphere through which it is viewed. Both the properties of your star and the make-up of your atmosphere will determine the final product -- it is an interplay between the two.

Your star from within earth's atmosphere will look different than it does on your alien planet.

But the colour of objects is quite a different process...

What color? What intensity?

That's entirely up to you! If all that matters is the effect and not the cause, then it can be whatever you want. The science part that would cause the nitpickers to react badly to your worldbuilding will be making sure the other aspects of your world are consistent.

Might this also affect the pigmentation of the planet's fauna?

Yep!

The colour of animal and plant life is adapted to absorb as much of the available spectrum as is ideal to allow that plant/animal to function. The visible colour of plantlife is actually the light that isn't absorbed by the plant. So, if a plant is green, it absorbs pretty much everything but green light.

Skin, though, does something a little different. Imagine if a plant had a layer of slime over it and that slime was different colours and opacities -- that's basically what skin is. People from northern climates tend to have pale skin tones, and people from equatorial climates tend toward darker skin tones. Like plants, the skin's colour is a result of what it isn't absorbing. But here's where it gets convoluted -- pale skin, contrary to common thought, isn't really due to pigmentation, per se. White people aren't really white -- it's more of a transparency thing.

As an organ, the skin protects us from damage, but also regulates the human equivalent of photosynthesis, which is the folate/vitamin D process. Pale skin simply allows more light to pass through the external layer -- less light is absorbed -- to hit the lower layers of the dermis. Darker skin absorbs more light, letting less light through to the lower layers. As people in equatorial regions experience hotter temperatures, they tend to have more skin exposed and thereby absorb too much light, and therefore produce too much vitamin D (which can be toxic). Dark skin regulates this process, allowing less light in through the skin by absorbing at the external most part of the body.

Animals with fur and feathers obviously don't have much light reach their skin. Instead, the light is absorbed by their fur and they get their vitamin D through grooming -- the fur/feathers synthesize vitamin and literally by eating their fur they get their vitamin D dose. We call this grooming.

You'll note that animals from northern climes change their coats. They get paler coats in the winter to maximize light absorption, and darker coats in the summer to reduce light absorption. (The camouflage thing is secondary, and part of the natural selection process.)

Other animals produce vitamin D internally, and have no need to get vitamin D from the sun. Their pigmentation is thus more-or-less unrelated to the sun.

Notably, though, creatures that live underground/deep water in the dark can be any colour. If they don't need light to synthesize essentials like vit. D, they'll typically have an opaque body and can be any colour. But if they DO have a photosynthetic/vitamin D function, they'll typically be absolutely pale -- they capture infrared light from heat sources. Fur, feathers, slime, etc., also adapts in opacity to allow or block light, as appropriate to environment.

And, of course, there are creatures in between, with some endogenous production and some external production.

In an nutshell, though, your animals will have hides, furs, feathers, carapaces, etc., idealized to their needs with respect to their environment. And if earth is anything to go by, your animals will be of every shape, size, and colour imaginable. :)

[BlueAngel]

chaching, thanks, I will post some chapters soon, once they're types up. I have them mostly handwritten at the moment.

Fung Koo, thank you so much for all that info. :)

If my alien atmosphere were to absorb and re-emit red light, then it migh be possible to have the remaining light appear in the blue spectrum, possibly violet or purple. If there is also a lack of dust in this atmosphere, then it may be possible that the blue light wouldn't be as scattered.

As I said before, I don't intend to go into too much detail on the composition, but that's not to say the alien species doesn't understand the workings of their world like we do ours. Thanks again for the help. :) ~Angela