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realmoh
Esoteric Dreamer
Joined: 2015-March-21
Location: Switzerland
Posts: 50
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| Posted: 2018-December-15 at 7:17am | IP Logged
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 Full Wallpaper View: 1920x1080
Ross 128 b: A confirmed supposed earth-like exoplanet, orbiting a near red dwarf at 11 lightyears distance.
This old planet receives about a third more radiation from its star than the earth from the sun, mostly in the infrared part of the spectrum. If the atmosphere is dense enough, it will be (well) tempered and perhaps there is water on the surface.
Here we are at the terminator of this world. Probably the planet is tidally locked, so the red dwarf sun will be pinned at the same place in the sky forever. The star’s apparent diameter is 4 times the sun’s diameter seen from earth and it’s about as bright as twilight on earth, just after the sun sets or just before sunrise. On this old and dried out seabed with huge cliffs fluorescent microorganisms are discharging energy from one of the rare flare events of the host star.
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nkalanaga
Star-faring Vagabond
Joined: 2004-August-13
Posts: 505
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| Posted: 2018-December-15 at 9:28pm | IP Logged
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Very nice! I like that the star isn't "red", as even cool red dwarfs are as hot as an incandescent light.
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realmoh
Esoteric Dreamer
Joined: 2015-March-21
Location: Switzerland
Posts: 50
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| Posted: 2018-December-16 at 2:10am | IP Logged
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Thank you very much! You're absolutely right. I try to depict Red Dwarfs a little more realistic than in other images I viewed. BTW: To a former render of mine I mentioned this statement about Red Dwarfs from the SF-Author Poul Anderson, I repeat it here:
„…At this point I must emphasize that the term „red dwarf” is misleading, as are color names for most kind of stars. We would not see a dull crimson ember. … Our star is certainly less brilliant than Sol. You could look straight at it for a little bit longer without suffering permanent eye damage, but only a little bit, and you wouldn’t want to. Its light has a yellowish tinge and at the distance of our imaginary planets there is significantly less than Earth gets, but human vision is so adaptable that ordinarily this won’t make any important difference. …”
Poul Anderson: Murasaki, Design for two worlds 1992 |
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nkalanaga
Star-faring Vagabond
Joined: 2004-August-13
Posts: 505
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| Posted: 2018-December-22 at 12:25am | IP Logged
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"at the distance of our imaginary planets there is significantly less (light) than Earth gets"
Very true, and important for agriculture and solar energy. Much of the red dwarf's energy output is infrared, where Sol peaks in the middle of the visible light range, so for the same temperature, there's less visible light.
Somewhat related, Sol from Pluto can still cause eye damage. It appears smaller, but per unit area, it is still the same brightness. It would burn a smaller spot on the retina, but would still be just as dangerous. Possibly more so, because the lower total brightness wouldn't cause one to look away as fast.
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realmoh
Esoteric Dreamer
Joined: 2015-March-21
Location: Switzerland
Posts: 50
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| Posted: 2018-December-22 at 1:39am | IP Logged
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I made some calculations for myself to receive an impression of the light conditions on Ross 128 b: Under the substellar point (Zenith, under a clear sky) it will be a illuminance of (more or less) 15000 lx. That will be about a „summer day in the shade”. At that point the luminance will be approximately 15 millions cd/m2. Enough to be blinded, when staring at the sun disk. At the terminator (my render) it will be illuminated about 1000 lx (that means on earth, the sun is just under the horizon) and the luminance will be about 1 million cd/m2. You may stare at the sun disk for a little longer than here on earth at sunset, but it will be more unpleasant the longer you stare at it.
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nkalanaga
Star-faring Vagabond
Joined: 2004-August-13
Posts: 505
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| Posted: 2018-December-30 at 1:34pm | IP Logged
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Interesting calculations. Thank you!
Even at the substellar point many Earth plants wouldn't grow well, making agriculture difficult. I wonder if future colonists of red dwarf systems will use mirrors to concentrate light for their crops?
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realmoh
Esoteric Dreamer
Joined: 2015-March-21
Location: Switzerland
Posts: 50
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| Posted: 2018-December-31 at 1:27am | IP Logged
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I think for plants adapted to (earthly) sunlight it will be difficult to grow under a red dwarf sun. Mirrors won't help much, because the maximum radiation is in the infrared. The colonists have to (genetically?) adapt the plants to (infra)red light. In literature you find, that hypothetically plants under a red star must be very dark/black to absorb the energy for growth/living.
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nkalanaga
Star-faring Vagabond
Joined: 2004-August-13
Posts: 505
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| Posted: 2019-January-06 at 3:21pm | IP Logged
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I suspect you're probably right. Plants use both the red and blue light in sunlight, and reflect the green. But the blue is more efficient. It takes two photons of red light for one reaction, while one blue photon is enough. Mirrors would increase the total usable light, which might allow them to grow, but that would also concentrate the IR, which would tend to overheat the plants.
If mirrors will work, they'd have to either transmit the IR, rather than reflecting it into the greenhouses, or the greenhouse itself would have to reflect the IR. Either is possible, but increase both the cost and complexity.
It might actually be cheaper to put the plants underground, and use solar power to light them. IR works fine for a thermal solar plant, and a steam boiler and generator is both simple and cheap to build, compared to a solar-cell factory. A colony orbiting a red dwarf might have more in common with a space station than a traditional farm.
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