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Because 75% of stars in our galaxy are red dwarfs, they seem like a good place for life to evolve in their habitable zone.  The problem with red dwarfs is they have gigantic flares that would be deadly to life in the habitable zone.  Also planets close enough to be in the habitable zone would be tidally locked.  What about a tidally locked, earth-like planet?  I've never heard this before, but what if life could thrive just out of reach of solar flares?  Suppose life could evolve just "over the horizon" of the solar flares?  The day side is too hot, the night side too cold, but the margin zone could be just right.  The margin zone of such a planet could be habitable, and shielded from solar flares by being located out of reach of solar flares.  Life would have liquid water in the margin zone, and because it is not directly facing the red dwarf, life could evolve to even intelligence if it stays just beyond the direct star light.

"Red dwarfs are often flare stars, which can emit gigantic flares, doubling their brightness in minutes. This variability may also make it difficult for life to develop and persist near a red dwarf.[41] It may be possible for a planet orbiting close to a red dwarf to keep its atmosphere even if the star flares.[42] However, more-recent research suggests that these stars may be the source of constant high-energy flares and very large magnetic fields, diminishing the possibility of life as we know it."

Red dwarf - Wikipedia

Edited by Airbrush
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Last night Science Channel's "How the Universe Works" addressed the potential for life evolving on a tidally-locked planet in the habitable zone of a red dwarf star.  The "margin zone" of a tidally-locked planet is blasted with constant hurricane winds.  So I think finding complex life, much less likely intelligent life, is not likely because of the high winds between the day and night sides of a tidally-locked planet near a red dwarf.  "Rare Earth" now seems more likely.

Edited by Airbrush
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Pure speculation.  High wind conditions could lead to evolution of very sturdy thick trunk trees which would mitigate winds and allow small (compared to tree size) animals to evolve.

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Isn't the Earth based dynamics at least partly responsible for the evolution of life [and extinction events]  on this planet? the plate tectonics, the 23.5 degree tilt, the Oceanic currents, the winds, the tides, the volcanic activity,  etc?

Edited by beecee
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Are we talking about "Eyeball Planets"? It seems there might be life on such worlds or there may not be on ice ball worlds. I have wondered if such planets might actually turn very slowly as Mercury does in our solar system due to tidal influences from other further away planets. This might result in a world where a dry desert slowly rotates to the night side while a glacier rotates into the sun from the icy side and melting ice turns to water and it transported by weather to freeze out on the night side. 

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On 4/2/2021 at 2:44 PM, mathematic said:

Pure speculation.  High wind conditions could lead to evolution of very sturdy thick trunk trees which would mitigate winds and allow small (compared to tree size) animals to evolve.

Maybe in the "margin zone" of a tidally-locked, Earth-like planet in the habitable zone, there could be VALLEYS that provide protection from the winds that make Earth's hurricanes and tornados look like summer breezes.  In those valleys there could be water and an environment where simple life could evolve to more complex forms.  But such a harsh environment would be a challenge for intelligence to evolve.

Edited by Airbrush
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Even if 3/4 of the stars in our galaxy are red dwarf stars, that still leaves 100 billion stars, out of a possible 400 billion, that are not. 

That is a lot of possibilities.

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On 3/31/2021 at 2:47 PM, Airbrush said:

Also planets close enough to be in the habitable zone would be tidally locked. 

It’s not obvious to my why this would be. 

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5 hours ago, swansont said:

It’s not obvious to my why this would be. 

The period over which tidal locking would occur is highly sensitive to the distance between the bodies, and varies by the distance to the power of 6.  It is less dependent on the mass of the primary.  The relationship ( assuming all else is equal)  is T = a^6/M^2

So, if we take a very luminous red dwarf like Lacaille 8760 with a mass of 0.6 that of the Sun, and a Earth equivalent position in the habitable zone of 0.268AU, you get a time period for tidal locking of roughly 1/1000 of the the time it would take for the Earth to tidal lock to the Sun. 

For a smaller star like Proxima Centauri at 0.12 solar masses and a habitable zone distance of 0.032AU, the tidal locking would take 1/13,000,000 of the time.

Red dwarfs also have spend a longer period in their pre-main sequence stage (a billion years or so), Thus a planet would be subject to tidal braking for a long period before even being considered as hospitable. 

So the odds are pretty high that a planet within the habitable zone of a typical red dwarf would be tidally locked. 

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Could possibly end up something like Venus too. With a day length about 117 times ours, it still maintains about the same temperature planet wide.

I was thinking most of the ecology could be airborne, with low lying or anchored surface and underground species providing mineral resources.

Edited by Endy0816
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"Due to differential heating, it was argued, a tidally locked planet would experience fierce winds with permanent torrential rain at the point directly facing the local star,[21] the sub-solar point. In the opinion of one author this makes complex life improbable.[22] Plant life would have to adapt to the constant gale, for example by anchoring securely into the soil and sprouting long flexible leaves that do not snap. Animals would rely on infrared vision, as signaling by calls or scents would be difficult over the din of the planet-wide gale. Underwater life would, however, be protected from fierce winds and flares, and vast blooms of black photosynthetic plankton and algae could support the sea life."

Habitability of red dwarf systems - Wikipedia

Edited by Airbrush
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