Color of Earth in colder stars

Hi, much passed since the last time I've posted in this forum.

I'm here with a new speculation... how would be the surface color of Earth if it was orbiting colder stars?

I'll show some images to show what I think:


A2V, F2V


G2V, K2V


M2V, L2V


T2V, Y2V

The image of G2v is the normal image. If you disagree with the colors, get the normal image.

It's fun to play with colors...

I wouldn't think that the difference in colour would be that obvious to the eye between adjacent spectral types.

Maybe, but if Earth was orbiting a red dwarf estar, surely the landscape would be redder. The brightness reflected in our buildings and bright surfaces would be redder. Maybe the sky and clouds would be also redder. Also, the brightness of the landscape orbiting redder stars are darker because these estars emit much less light, so I think that it is obvious that Earth would be darker too. The sky would be less blue because M stars emit much less blue light... maybe the sky would be more to green or yellow. Or even white. Or lillac...

For example, we live in this Earth, but if we gone to Earth in a parallel universe that orbit a, let's say, M5V star, it would be very different from Earth orbiting a G2v star, right? Also for the fact that it would be tide locked too. On the other hand, if Earth orbited A2 star or a F star, the landscape surelly would be much brighter, maybe even more to blue. Because such stars emit much more light than our sun. I think plants would have a different color, such as if Earth orbited red dwarfs too.

Maybe the brightness for a M star would be equivalent of a K2V star in the pictures... But the landscape would be redder for sure!

Maybe Earth would look like this in a M5V star, instead of K2V star...

Maybe the effect of color of a K star, in Earth, would be minimal, but the effect of color would be higher in a M star...

And even higher in a brown dwarf!

Around stars of ~3500 K temperature (e.g. GJ 876), effects of Rayleigh scattering and the stellar spectrum should cancel out. A clear sky would therefore appear grey. Furthermore the temperature of a red dwarf is comparable to a typical incandescent light bulb, so the light would still appear fairly white.

Ok, the sky would not be blue...

But is there any chance the sky could be green, yellow? I mean, since M stars emit very few blue light, but may still emit light average light on green or yellow... The Rayleigh scattering would cancel in blue light, but what about other colors?

I mean that Rayleigh scattering light in earth-like planets orbiting M5V stars to below could scatter not blue, but colors more next to red, maybe... If the sky is grey, maybe the clouds will have a tinge of yellow, due to the dominant color at such temperature. The dominant color of sun is close to white. I don't agree a red dwarf star would look white in the sky, but at least a bit yellow.

I mean, if you put a white surface to be reflected by the light of such star, maybe the light reflected will be a bit yellow, not completely white, as our sun would reflect, due to it's near white main color. Here's the color represented for each temperature...



As the above image shows, the color of the sun, according to its temperature, is a yellow that is more white than yellow (above 5500K), but say, a M5V star (about 3500K) is pretty yellow. Because it's a star with not saturated color, white surfaces reflected by the light of such star would be more yellow than white. Because of that clouds would appear yellow than white. Buildings with white walls would reflect yellowish color instead... also, when the M5V is near the horizon, the landscape would be redder than on Earth, for sure!


So I think the landscape color in this image would still be plausible for a world orbiting a M5V star.

But maybe I have forgotten some more details...

Thing is colour perception is not absolute - fact is you can perceive the illumination from both sunlight and a filament light bulb as "white" even though one comes from a ~5800 K source and one from a ~3000 K one. The colour chart should be interpreted more as relative colour (and that at a situation where the light is dim enough not to saturate your colour receptors)

Yeah, cause I have one light bulb, and the walls appear white.
While another person says it's too dark. Sees it as gray.


The color of the pics you have above will likely be more of a factor towards the constitutes in the atmosphere before the star type.

Ok, I understand the constitutes of the atmosphere can change the color of the surface. And Ok, the color of the surface would not be so much different in a red dwarf star (because we also see white through light bulbs). Maybe at least in a brown dwarf, i guess (the light of brown dwarfs are very red)?

But about the color of the sky, people here said it would be white or gray, and not blue. But why not green, yellow or even red in planets orbiting colder stars such as Proxima Centauri?

For the results of what happens if you calculate the sky colour assuming the same total incident radiation on the planet (i.e. including non-visible light), see here.

(Which reminds me I need to get back to work on my Gliese 876 Celestia add-on...)

If the sky of a world around a M star would be grey, and if the clouds would be yellowish, maybe the sky on Earth would be like this...

I know when I use different temperature bulbs for my aquariums, the appearance is different. The "standard" aquarium bulb is in the 3000K range, while some have K ratings of 10,000 or even 20000.

I had replaced my "full sun" bulb (approx 5500 K) with a 6500 K bulb and everyone who saw the tank asked why did it seem to glow green.

Usualy fish tank bulbs are not "blackbodys", or may be your tank is very very hot!

It would stand to reason it's a simulated temp...the bulbs show where it's peak spectra is, but when they're in operation, the bulb itself looks white.

-M-

Sunchaser wrote:

It would stand to reason it's a simulated temp...the bulbs show where it's peak spectra is, but when they're in operation, the bulb itself looks white.

-M-

But the colors are "false", because the total light looks like XXXX K for human eyes, but not every wavelight are realised like in a blackbody, so colors of objets under fish tank bulbs look false.

For information, under some fish tank bulbs (i tink the "day light" ones), plants are just unable to growth because of the lack of vital wavelight.