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» Hatrack River Writers Workshop » Forums » Open Discussions About Writing » Red Stars

   
Author Topic: Red Stars
Osiris
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A quick research question for a story I'm working on. Anyone have any idea what an icy tundra-like landscape would look like on a planet lit by a red dwarf star?

On earth, this landscape would look like the Arctic. My assumption is that there'd be a reddish tint to everything, but I'm not certain and just wanted to get a second opinion.

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extrinsic
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If the red dwarf's radiation and the planet's atmosphere and climate support life as we know it, the sky and water and ice would appear blue due to Rayleigh scattering. Surface light would not be appreciably different from what Earth light looks like. Some of the Sun's red spectrum light wavelength is screened out by our atmosphere. The same would happen to light from a red dwarf shining through a planet's similar atmosphere. Eyes like ours would soon compensate for any red light predominance.

If a visitor, he or she would see a rose colored tint for a few hours. If a native, he or she or it probably wouldn't notice a red tint. Try wearing rose colored eyeglasses for a day. You'll see what your permafrosted icy tundra looks like when looking at, say, a white sheet spread on the ground.

Also, sunlight at sunset passes through more refractive atmosphere and warm red light shines down. At morning's sunrise, though, sunlight is blued and cool, due to Rayleigh scattering and passing through less refractive atmosphere. The red dwarf planet's light would be optically warm.

However, the above assumes eyes structured like humans' cones and rods. Maybe natives would be red-color blind. Or maybe they only see in shades and hues of red.

[ December 11, 2012, 10:08 PM: Message edited by: extrinsic ]

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MattLeo
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That's not so simple. On Earth the ice would be sky-lit because of Rayleigh scattering of blue photons in the atmosphere. That'd still be the case for a red star; stars approximate black bodies, so even a red star would put out plenty of blue light. So you'd still have the ice illuminated bluish scattered light (only darker), combined with direct red light.

This is complicated by the fact that color is a complicated physiological phenomenon and not simply a measure of wavelength. Mix red and blue light and you get magenta or fuchsia.

Hmm. I think what you want to do is find a photo of an antarctic sunset, in which Sol's rays are red and there's a dark blue sky. Something like one of these:

https://www.google.com/search?as_st=y&tbm=isch&hl=en&as_q=antarctic+sunset+sunrise&as_epq=&as_oq=&as_eq=&cr=&as_sitesearch=&safe=active&orq=&tbs=itp:photo,ic:specific,isc:pink&tbo= d&biw=1280&bih=613&sei=5vPHUJeVN4Lh0gH7moHYAQ#hl=en&safe=active&tbo=d&as_st=y&tbs=itp:photo%2Cic%3Aspecific%2Cisc%3Apink&tbm=isch&sa=1&q=antarctic+sunset+sunrise+dusk&oq=antarctic+ sunset+sunrise+dusk&gs_l=img.12...0.0.2.154895.0.0.0.0.0.0.0.0..0.0.pchatac..0.0...1.cyMKdmJ7FnI&pbx=1&bav=on.2,or.r_gc.r_pw.r_cp.r_qf.&bvm=bv.1354675689,d.dmQ&fp=92fe2bd52fa2e36a& bpcl=39650382&biw=1280&bih=613

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MattLeo
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extrinsic brings up an important point: it's almost certain that that natives will have different color vision.

On Earth, reptiles and birds have *four* primary colors as opposed to most mammals which have only three. This means they see colors (or it might be better to say they *discriminate* colors) we can't. A starling looks black with a little iridescence to us; it might look very different to other starlings.

Early mammals were nocturnal, and the cones for the fourth primary color evolved into light-sensitive (but not color discriminating) rods. The remaining three primary colors shifted somewhat in spectrum to compensate.

I'll disagree slightly with extrinsic on human eye adaptation to a new spectrum. I think that is more behavioral than perceptual. I changed my house from incandescent lights to day spectrum fluorescents. I can tell the difference between a room lit at 2700K and one lit at 5500K, even if I've been in the room for some time, I just don't notice it.

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Grumpy old guy
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It gets even worse; the light emitted by every red dwarf will be slightly different in both wavelength, luminosity and, damn! can't think of the third thing.

Blast! Can't remember, been a busy day. Anyway, make it look any way you want it to, no one is going to be able to prove you wrong. Well, not for a while anyhow.

Phil.

PS Ahh . . Watson saves me: the surface temperature of the star will also affect the light's wavelength.

P.

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Grumpy old guy
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Osiris, I only just realised how unhelpful my advice was. Here's what I would do:

First, choose an actual red dwarf star. For a story I'm writing I did a search on Earth analogue stars within a hundred light-years. I ended up with forty to choose from.

Second, do an internet search on the spectral analysis of the star you have chosen. This will yield a load of information you won't understand unless you're an astrophysicist.

Third, start studying and researching what all that information means. Buckle the seatbelt tight, you're in for a bumpy ride. Or try four:

Ask your local astrophysicist for help. That could be NASA, or the local university. You might get a response. You can hope for one, or make it up as you go. Don't forget, the colour will be influenced by the composition of your planet's atmosphere, particularly its trace elements.

Phil.

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MartinV
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OK, no need for me to explain it. [Wink]
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MattLeo
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quote:
Originally posted by Grumpy old guy:
Osiris, I only just realised how unhelpful my advice was.

If I only had a nickel for every time I woke up in the middle of the night with that realization...
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Osiris
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Spectacular, thanks guys! My protagonist is a human visitor to Gliese 581d, so he'll have rods and cones. The res dwarf and planet are already selected. I'm not sure if we know what kind of atmosphere Gliese 581d has, though.

I had the thought to look at some sunset pictures of Antartica, but I figured the answer was more complicated then that.

I only get hung up on these details enough to create plausibility. I try not to let exact certainty get in the way of telling the story. [Smile]

Thanks again all, and thanks Matt for the photos. I'll use those as a reference.

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extrinsic
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Current knowledge about Gliese 581d is that its gravity is three times Earth normal and has surface water, habitability compared to Earth 1: 0.74. Servo exoskeletons and flotation suit compensators anyone? Shiny fresh and brand-nam-new from AckMay's Ordlay, Inc.
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Osiris
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I'm projecting improvements in materials will lead to an improved Bio-Suit that will make an exoskeleton unnecessary. Since Gliese 581d is on the outside edge of the habitable zone, I'm going with an icy surface. Hey, astronomers can be wrong, ever so slightly. [Smile]

Now the question is, how many of the other four planets in the system would be visible in the Gliesian sky at a given time?

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extrinsic
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Check out astronomy freeware that allows users to see naked eye simulations. Celestia comes to mind. But it's a resource hog and as addictive to use as a role playing game.

The Celestia home page;
http://shatters.net/celestia

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MattLeo
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Hmm. Gliese 581 may be a red dwarf, but it's not all that red. The coronal temperature is 3480K which is actually a bit bluer than a typical halogen light bulb.

Color Temperatures

2600K -- Teide 1 (M8 spectral type)

2700K -- Incandescent bulb.

2800K -- Alpha Herculis (M5 spectral type)

3000K -- Halogen bulb.

3140K -- Betelgeuse (M2 spectral type)

3450K -- Gliese 581 (M2 spectral type)

5778K -- The Sun (G2 spectral type)

9940K -- Sirius (A1 spectral type)

I suspect that even a "red" M2 star like Betelgeuse would look white while in it own system -- albeit somewhat dingier white than the Sun. The Sun is a "yellow dwarf" but it looks white to us; I think that'd be because here on Earth even the blue light rods in your eye (with a maximum response at 450 nm) are overwhelmed. Out by the Oort cloud the Sun probably looks quite yellow.

It might be interesting to compare an incandescent bulb with a halogen bulb looking through different neutral filters. I bet an incandescent looks orange through a dark filter.

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Grumpy old guy
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Another interesting thing about the spectral analysis of stars is that it hints at the stars elemental construction. I was just browsing so I can't remember which star it was, but it had a very low amount of beryllium in it, which would effect the make-up of the planets as well. What if a sun had a very low iron content. What would be the major source of metal on an inhabitable planet around such a star -- or would they 'develop' alternatives.

Ah, the universe . . . ya just gotta love it!

Phil.

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