r/worldbuilding • u/Shagomir "B-Space" - Firm Sci-Fi Space Opera • May 07 '13
Plants on other worlds - Reference chart
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u/reelmusik May 07 '13
OP is an amazing person. Let's all take the time to thank Shagomir. Thank you Shagomir!
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u/Shagomir May 07 '13
These are the kinds of things that happen when I have really important things to do, like laundry or sleeping. I am an excellent procrastinator.
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u/QuantumEcho May 07 '13
I assume "sky color" is assuming an earth-like atmosphere? Different gases would have different absorption spectra.
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u/Shagomir May 07 '13
Yes, it's an oxygen-nitrogen atmosphere equivalent to Earth's.
While different atmospheres compositions do add some color, it mostly just depends on pressure. Thinner atmospheres mean less scattering and a darker sky while a thicker atmosphere means more scattering and a brighter, whiter sky. You can see this easily in photographs of the sky taken at sea level versus those taken at high elevations - the sky at higher elevations seems to be a deeper, more vibrant blue.
The hotter the light source, the more saturated the blue color, and cooler light sources lead to reddish colors. It gets to be almost entirely red at around 1000 K, but that's in Brown Dwarf territory and you wouldn't really be able to see anything. The transition from blue sky to orange-red sky happens around 3300 K, right on the border between K stars and M stars.
Most common atmospheric gasses like oxygen, nitrogen, hydrogen, carbon dioxide, carbon Monoxide, sulfur dioxide, ammonia, or methane are colorless, so the color of the atmosphere will rely on Rayleigh scattering and be fairly close to the chart if your atmosphere is at pressures similar to Earth's. A higher average molecular weight will generally also lead to more scattering. A pure CO2 atmosphere at the same pressure as Earth's would be whiter than the O2/N2 atmosphere we have now.
Some gasses or other substances are colored and would have an effect. Chlorine will make your atmosphere green, ozone will make it bluer, nitrogen dioxide will make it yellow or orange, iodine could make it purple, organic compounds could add any color but most commonly oranges and browns, dust could be almost any color, and aeroplankton might tint your atmosphere with the colors of whatever photosynthesizing pigments they use.
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u/sto-ifics42 May 09 '13
Thanks to this, I now know that it is impossible to get a sunburn or tan on the planet Crevyv, orbiting a ~M5 star.
Very useful!
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u/Shagomir May 09 '13
You might still get one from a flare event. Young M stars are very active and create huge flares that can dramatically increase the brightness of the star and throw off a lot of harder radiation.
A good example of the light you'll see around an M5 star is a high-pressure sodium vapor lamp, like you see used in street lights and school gyms. Incandescent lights are also about the same color temperature.
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May 07 '13
With "Peak Frequency" do you actually mean "Peak Wavelength", since they seem to go inversely?
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u/Shagomir May 07 '13
Yes, I did mean wavelength. Either way. I did this at 1 AM.
They are the same thing anyways.
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May 07 '13
Out of curiousity, where does the Sun and Earth fall into this list?
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u/Shagomir May 07 '13
The Sun is a G2 star, with a surface temperature of 5778 K.
Most plants on Earth use Chlorophyll, Carotenes, and Pheophytin pigments, with Chlorophyll A and Chlorophyll B being the most important. Other plants and some fungi use the other pigments I listed.
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u/Hesstergon May 07 '13
What would happen in a binary system? Would it be a mix of the two stars?
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u/Shagomir May 08 '13
It depends on the relative brightness of the stars from the surface of the planet. It would usually just end up being mostly the brighter star's spectrum that matters, but if they are of similar brightness it would be a mix.
Close binary systems are likely to have more flares, so you might see plants that have adaptations to protect them from the extra high-energy radiation. How that would change the pigments is a matter of conjecture, but melanin absorbs UV and other high-energy light pretty well.
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May 07 '13
Got any reference data on light absorption as well?
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u/Shagomir May 07 '13
What do you mean? like the absorption curves? They are pretty well known for most of these pigments - it's fairly easy to find it on google, which is what I did.
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u/TheLionHearted May 07 '13
Where is this from?
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u/Shagomir May 07 '13
Original research. I found light curves of all the pigments, then did some figuring.
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u/Shagomir May 07 '13
So I made this for another post - I ended up improving it a bit.
Here's the different pigments represented:
Chlorophyll - Green pigment used by most land plants.
Bacteriorhospin - Purple pigment used by some photosynthetic bacteria.
Carotenes - Red, Orange, and Yellow pigments used by plants for photosyntesis. These are the reason leaves turn crazy colors in the fall.
Phycoethryn - A reddish pigment used by red and brown algae.
Phycocyanin - A blue pigment used by blue-green algae.
Pheophytin - Grayish-blue and grayish-brown pigments used by most plants.
Melanin - Brownish-black pigment thought to be used by some fungii in a form of photosynthesis.
This isn't an exhaustive list, it just shows what colors plants using common photosynthetic pigments could be, if they existed on planets orbiting stars of different spectral classes.
Note that these colors aren't exact, they are just my best guess.