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I recently came across a planet that I found pretty interesting but I can't seem to find much information about its characteristics. Its atmosphere is pink in appearance. After looking at the picture a bit, you can see that the pink hue couldn't be caused by the color of a gas in the atmosphere because that would make the planet appear slightly opaque.

enter image description here On earth, when sunlight reaches its atmosphere, it's scattered in all directions by all the gases and particles in the air. Blue light is scattered in all directions by the tiny molecules of air in Earth's atmosphere. Blue is scattered more than other colors because it travels as shorter, smaller waves.

So If the same process happened on this planet, what gases in its atmosphere could scatter light to make the atmosphere pink in hue when the parent star is behind it?

I didn't make this picture. I didn't add anything to it before posting this question. From what I found, this picture was created by a google plus user named Lerne Seref

If I need to change anything about this question, let me know.

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    $\begingroup$ Please, link to source of your images and make sure they are CC-compliant. $\endgroup$
    – Mołot
    Commented Oct 2, 2018 at 9:46
  • $\begingroup$ It could be a gas. On the edge you are looking through far more atmosphere than directly at the planet, thus if there is any color it is likely to appear there, strongly backlit by a star, than through the thinner atmosphere weakly backlit by refracted light. Further, the planet is too dark for us to say the atmosphere in front of it is completely transparent; we have no reference image with better lighting. An unusual gas in the atmosphere is an entirely plausible explanation; and no amount of refraction will explain the color, which is red + blue, at different ends of the spectrum. $\endgroup$
    – Amadeus
    Commented Oct 2, 2018 at 11:23
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    $\begingroup$ @Amadeus: Actually violet is a perfectly cromulent spectral color. Color is not a physical quantity; it is a sensation which exists in the mind, and it so happens that for the human visual system a mixture of red and blue is indistinguishable from monochromatic violet. (Hint: computer monitors make yellow from red and green; this does not mean that all sources of yellow light actually emit a mixture of red and green.) $\endgroup$
    – AlexP
    Commented Oct 2, 2018 at 11:53
  • $\begingroup$ @AlexP It depends on whether we call the color in the picture purple, or violet. To me it looks purple. Violet is a single wavelength; Purple is not, it is a mixture of red and violet wavelengths. See here: en.wikipedia.org/wiki/Purple AND here: en.wikipedia.org/wiki/Visible_spectrum#Spectral_colors $\endgroup$
    – Amadeus
    Commented Oct 2, 2018 at 13:11
  • $\begingroup$ @AlexP Except that this purple (pink) isn't violet, which is at the extreme end of the visible spectrum. Violet is approximated on computer screens by a 1:2 combination of red:blue, this purple appears more like 1:1. $\endgroup$
    – GretchenV
    Commented Oct 2, 2018 at 13:13

4 Answers 4

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The magenta is a sunset as seen from space.

In situations where the light that comes to your eye is not direct from the source, that light is scattered or bounced off of the medium it is traveling through. The more the light scatters and bounces, the more of it can change path and make it to your eye. Short (blue, indigo, violet) wavelengths scatter and bounce more. That is why the sky is blue - it is lit indirectly and more of the blue bounces back down to your eye. That is why water is blue - of all the light entering the water, the short wavelengths come back out to your eye.

(I just realized this phenomenon explains why a pure note whistled in a stairwell will echo slightly sharper! Woo!)

The converse is true for a sunset or sunrise. The light is coming straight at your eye from the source. When coming through an atmosphere, shorter wavelengths scatter away but the long wavelengths (reds) punch through whatever is scattering the light and keep going. That is why sunsets are red and smoke / dust make redder sunsets.

- The planet - I conclude it is being lit from behind and we are seeing the equivalent of a sunset refracted around through the atmosphere. The refracted light has travelled a straight (although refracted) path and so is redder. Some of the blue is still present scattering back which tints the red towards magenta. You can sometimes see this in the sunset.

sunset

http://lightexhibit.org/bio_image80.html

At sunrise and sunset, light from the Sun must take a much longer path through the Earth's atmosphere than it does during the middle part of the day. This means more of the blue and indigo light of sunlight is scattered away because these shorter wavelengths of visible light are more affected by air molecules in the atmosphere. This often allows more of the red and orange light to reach the Earth's surface. Other factors -- including dust, pollution, haze, and cloud formations – may also affect the colors of a sunset, creating a more complicated palette of light as the Sun dips below the horizon

What a great picture. I think it is unmodified because they are using it as exactly the example I want.

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Being pedantic - I do not think we would see the illuminated swath at 10 oclock if the only available light were such as to produce the magenta sunset effect. I conclude that this celestial body must have 2 light sources - one illuminating the top left and the other almost completely behind the body, refracting around the edge as the sunset. A star and large reflective moon could team up this way.

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When Mt. Pinatubo erupted the sky and sunsets were noticeably pinker than usual, although this won't be the driver of your photo. Similar phenomena were reported after the 19th century eruption of Krakatoa. If you really want a pink atmosphere, though, you could have a world with substantial volcanic activity maintaining levels of dust in the atmosphere.

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What could be causing this planet's atmosphere to be pink in hue?

The most probable cause of the pink is artistic licence since this is not an unadulterated picture of a real planet.

Alternatively and very unlikely is that it is part of an eclipse where the light from the star is pink. In which case it's extremely badly drawn.

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  • $\begingroup$ @WitherFang136 Photoshop or a bunch of others. 'not' was in the original, I added 'most probable' $\endgroup$
    – Kilisi
    Commented Oct 2, 2018 at 10:41
  • $\begingroup$ Before deciding if this is an answer or not, I want to hear a clarification from the OP on their actual question. This one seems to be answering "why this particular photo has a pink color?". $\endgroup$
    – L.Dutch ♦
    Commented Oct 2, 2018 at 10:49
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    $\begingroup$ @WitherFang136: The question does not ask what natural processes could make the atmosphere look violet when seen from space with the sun behind the planet. The question asks why the atmosphere of the planet depicted in this specific picture actually does look violet when seen from space with the sun behind the planet. Kilisi explained that the picture is made up and the most probable cause is artistic license. I don't understand your objection. (I for one think that chromatic aberration in a cheap long photographic lens may also be likely.) $\endgroup$
    – AlexP
    Commented Oct 2, 2018 at 10:49
  • $\begingroup$ @L.Dutch I just answer the question as posed, not much point deleting my answer because it doesn't answer a question that wasn't even asked. $\endgroup$
    – Kilisi
    Commented Oct 2, 2018 at 10:53
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    $\begingroup$ @Kilisi If you wish to protest a mod deletion, flag the deleted post for moderator attention and request review of the deletion. Don't simply re-post the same content. $\endgroup$
    – user
    Commented Oct 2, 2018 at 10:59
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A CO2 atmosphere scatters longer wavelengths of light than our Oxy-nitro atmosphere, and the suspended dust particles make it even redder.

In the case of this image, if taken from the Earth, the "atmosphere" could easily be an artifact of Earth's own atmosphere, and the colors an artifact of diffraction. I have also seen this effect when viewing the moon through a telescope on a clear summer evening, due to a combination of optics and atmospheric diffraction.

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