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I've been thinking about a fantasy setting built around the idea of a habitable, tidally-locked world orbiting a red dwarf. Since it is fantasy I do have some leeway in terms of the real world limitations such a world might face when it comes to complex earthlike life and civilization, but I would rather find ways to incorporate such limitations into my worldbuilding whenever possible.

My first question has to do with the effects the light of the star would have on human skin. I could find plenty of information about the dangers of flares, but not a whole lot about the regular sunlight of a red dwarf. So, assuming an atmosphere similar to Earth's and that the star is not flaring, would it be possible to walk around in the open at the twilight zone with exposed skin?

NOTES: This idea is in a very early stage of concept and I'm quite new to worldbuilding, so I have no specifics to give about the planet in question. All I know is that my planet is tidally locked, in the habitable zone and livable at the terminator. Also, concerning atmosphere, I require the planet to be able to sustain human life without the need for advanced technology, so, for the purposes of this question, I'll just assume the atmosphere is Earthlike and somehow managed to hang on to the planet despite the star flares.

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  • $\begingroup$ Distance? Atmosphere? Are you handwaving atmosphere existence and composition under flares? $\endgroup$
    – Mołot
    Nov 14, 2018 at 23:01
  • $\begingroup$ For the purposes of this question, yes, I'm handwaving atmosphere. As I said, assume Earth's atmosphere. How it came to be or remained in place is not important to me at the moment. I also don't have specifics such as distance. I don't have a lot of experience with worldbuilding so I wouldn't know where to place the planet. Besides this is very early stages of concept. All I know is that it is in the habitable zone and livable at the terminator. If there is any distance to the star where walking around in common clothing is possible, then I might keep going from there. $\endgroup$
    – Vorterox
    Nov 14, 2018 at 23:29
  • $\begingroup$ Hello and welcome. I missed you are new. When you will have time, take the tour and see [help center]. For now, just remember this site is not a forum. Comments are meant to be place when we ask for clarifications etc, but actual clarifications should be edited directly into question. $\endgroup$
    – Mołot
    Nov 14, 2018 at 23:31
  • $\begingroup$ Silly me, I posted bad link to help center. Here you go ;) Of course, you have probably found it anyway already if you wanted. $\endgroup$
    – Mołot
    Nov 14, 2018 at 23:46
  • $\begingroup$ Thank you for your help. I'll be editing the questions from now on. $\endgroup$
    – Vorterox
    Nov 14, 2018 at 23:49

2 Answers 2

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Light from a red dwarf is weaker than light from a normal star.

The fact that it is red means it's producing lower intensity wavelengths.

So yes you can streak to your heart's content, though there would still be some UV so don't spend all day frolicking in the nude.

How long? Depends on your star's output and the atmospheric conditions of your location.

Perceived temperature is negligible. If Earth is the same environmentally in both scenarios then its position is different with respect to the star. Also if it is the same environmentally then the amount of heat it is receiving is also the same, ergo the temperature is the same.

Clothing? Well, if you are at the poles it's going to be cold so bundle up.

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  • $\begingroup$ "means its producing lower intensity wavelengths" - Not quite. They can be brighter than white dwarfs. They are just cooler and thus more red - but total amount of energy for Earth-like planet in habitable zone would be similar to what sun gives us. And strictly speaking, wavelength does not have "intensity", only, well, wave length. $\endgroup$
    – Mołot
    Nov 14, 2018 at 23:39
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    $\begingroup$ A white dwarf is not a normal star. Red (towards infrared) is a lower intensity wavelength as blue (towards UV) is a higher intensity wavelength. Even though its irrelevant to my point luminosity does increase with wavelength intensity with respect to general star classification. And finally my point was that if both planets are the same habitability then they are receiving the same energy so the temperature is the same. $\endgroup$
    – anon
    Nov 14, 2018 at 23:52
  • $\begingroup$ On a tidally locked planet, the poles are permanently on the boundary between night and day, so the temperature should be cold, but not as cold as the far side of the planet. $\endgroup$
    – CJ Dennis
    Jan 6, 2020 at 6:28
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Yes, if the planet is close enough - regarding flaring, with a large dense planet maintaining sufficient rotation, there may be a strong enough magnetosphere to slough off the added hazard of solar flares pretty effectively.

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  • $\begingroup$ "there may be a strong enough magnetosphere to slough off the added hazard of solar flares pretty effectively." But to the point where people would have no need to take cover during the flares? Also, I suppose such a magnetosphere would create pretty stunning auroras in the sky; would they be visible from the twilight zone? $\endgroup$
    – Vorterox
    Nov 14, 2018 at 23:55
  • $\begingroup$ hard to say, i'm not an expert. but yes the auroras would be extraordinary, visible at lower latitudes. $\endgroup$
    – theRiley
    Nov 15, 2018 at 0:10
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    $\begingroup$ Flares produce two kinds of hazards: electromagnetic, and charged particle. A magnetosphere will protect from the charged particle radiation, but not UV / X-rays / really intense visible light. For that, you just need mass in the way--enough atmosphere, or water, or a roof to block it. $\endgroup$ Nov 15, 2018 at 0:38

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