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New Alpha Centauri data
Erik Max Francis wrote in message ...
Jonathan Silverlight wrote: It's interesting to compare that with the depiction in David Hardy's painting "Proxima's Planet" - I've got the print over my desk. He shows them in a dusty red sky, which makes sense as -6 stars would be visible in daylight even on Earth with our blue sky, but they are about one inch (2.5 cm) apart which corresponds to at least a couple of degrees at normal viewing distance. But this only takes into account the brightness of the A and B components. Proxima itself would be very bright, because for it to be in the habitable zone (presuming that's where it is, I'm not familiar with the painting), the planet needs to be very close to Proxima. For it to be in the habitable zone, in fact, it needs to be at a position where the intensity of sunlight is the same as at Earth's orbit, which means that Proxima will have the same brightness as the Sun, about magnitude -27 -- a little less because Proxima has enough infrared excess that that will go into heating the planet a little, requiring less raw illumination in the form of visible light. Do you have any idea how much less? A and B will be easily visible, but most of the illumination will come from Proxima itself. It will be a cool, red light, but it will be nearly as bright as the Sun on a full day. Almost by definition. How large bolometric correction towards red would be acceptable for terraforming? On Earth, temperate and tropical shadow-tolerant land plants habitually grow in 1/100 of total sunshine. Indeed, photosynthesis suffers from "light inhibition". But what light they do get has a lot of blue (scattered from sky) or at least red (filtered through leaves of other plants). How low light temperature can plants evolved on Earth endure? And what would be the corresponding bolometric correction? |
#2
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New Alpha Centauri data
Jaak Suurpere wrote:
Do you have any idea how much less? Someone else compared the bolometric magnitudes, which is a pretty good first order approximation (the total influx of stellar energy would be the same, but a red star would appear significantly dimmer than a yellow one). By that reckoning it would be a difference of about 4 magnitudes (less than a factor of 100 in illumination), but that only brings the the magnitude from -27 to something like -23. How large bolometric correction towards red would be acceptable for terraforming? I have no idea. -- Erik Max Francis / / http://www.alcyone.com/max/ __ San Jose, CA, USA / 37 20 N 121 53 W / &tSftDotIotE / \ Listen to my song \__/ Chante Moore Lsystem / http://www.alcyone.com/pyos/lsystem/ A Lindenmayer systems explorer in Python. |
#3
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New Alpha Centauri data
Erik Max Francis wrote in message ...
Jonathan Silverlight wrote: It's interesting to compare that with the depiction in David Hardy's painting "Proxima's Planet" - I've got the print over my desk. He shows them in a dusty red sky, which makes sense as -6 stars would be visible in daylight even on Earth with our blue sky, but they are about one inch (2.5 cm) apart which corresponds to at least a couple of degrees at normal viewing distance. But this only takes into account the brightness of the A and B components. Proxima itself would be very bright, because for it to be in the habitable zone (presuming that's where it is, I'm not familiar with the painting), the planet needs to be very close to Proxima. For it to be in the habitable zone, in fact, it needs to be at a position where the intensity of sunlight is the same as at Earth's orbit, which means that Proxima will have the same brightness as the Sun, about magnitude -27 -- a little less because Proxima has enough infrared excess that that will go into heating the planet a little, requiring less raw illumination in the form of visible light. Do you have any idea how much less? A and B will be easily visible, but most of the illumination will come from Proxima itself. It will be a cool, red light, but it will be nearly as bright as the Sun on a full day. Almost by definition. How large bolometric correction towards red would be acceptable for terraforming? On Earth, temperate and tropical shadow-tolerant land plants habitually grow in 1/100 of total sunshine. Indeed, photosynthesis suffers from "light inhibition". But what light they do get has a lot of blue (scattered from sky) or at least red (filtered through leaves of other plants). How low light temperature can plants evolved on Earth endure? And what would be the corresponding bolometric correction? |
#4
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New Alpha Centauri data
Jaak Suurpere wrote:
Do you have any idea how much less? Someone else compared the bolometric magnitudes, which is a pretty good first order approximation (the total influx of stellar energy would be the same, but a red star would appear significantly dimmer than a yellow one). By that reckoning it would be a difference of about 4 magnitudes (less than a factor of 100 in illumination), but that only brings the the magnitude from -27 to something like -23. How large bolometric correction towards red would be acceptable for terraforming? I have no idea. -- Erik Max Francis / / http://www.alcyone.com/max/ __ San Jose, CA, USA / 37 20 N 121 53 W / &tSftDotIotE / \ Listen to my song \__/ Chante Moore Lsystem / http://www.alcyone.com/pyos/lsystem/ A Lindenmayer systems explorer in Python. |
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