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+--- Thread: The Red Sky Paradox (/thread-11485.html)
The Red Sky Paradox - C C - Dec 29, 2021
https://www.sciencealert.com/why-the-heck-aren-t-we-orbiting-a-red-dwarf-star
EXCERPTS: . . . Not only do red dwarfs make up as much as 75 percent of all stars in the Milky Way, they are much cooler and longer-lived than stars like the Sun. Much, much longer lived.
We expect our Sun to live around 10 billion years; red dwarf stars are expected to live trillions. So long, in fact, that none have yet reached the end of their main sequence lifespan during the entire 13.4 billion years since the Big Bang.
Since red dwarfs are so abundant, and so stable, and since we shouldn't automatically consider ourselves to be cosmically special, the fact we're not orbiting a red dwarf should therefore be somewhat surprising. And yet, here we are, orbiting a not-so-common yellow dwarf.
This, according to a paper by astronomer David Kipping of Columbia University, is the Red Sky Paradox – a corollary to the Fermi Paradox, which questions why we've not yet found any other forms of intelligent life, out there in the big wide Universe.
[...] In his paper, Kipping lays out four resolutions to the Red Sky Paradox.
Resolution I: An Unusual Outcome. The first is that, well, we're just a freaking oddball. If the rates at which life emerges around both star types are similar, then Earth is an outlier, and our emergence orbiting the Sun was just a random, one in 100 chance.
That would create tension with the Copernican principle, which states that there are no privileged observers in the Universe, and that our place in it is pretty normal. For us to be outliers would suggest that our place is not so normal. [...]
Resolution II: Inhibited Life Under a Red Sky. Under this resolution, Kipping argues that yellow dwarfs are more habitable than red dwarfs, and, as a consequence, life emerges far less often around red dwarfs – around 100 times less. There's lots of theoretical evidence supporting this idea. Red dwarfs, for instance, tend to be rowdy, with lots of flare activity, and don't tend to have Jupiter-like planets. [...]
Resolution III: A Truncated Window for Complex Life. Here, the argument is that life simply hasn't had enough time to emerge around red dwarf stars. [...] This could mean that the window for complex biology to emerge on rocky planets on white and yellow dwarfs is a lot longer than it is on red dwarfs...
Resolution IV: A Paucity of Pale Red Dots. Finally, although around 16 percent of red dwarfs with exoplanets are listed as hosting rocky exoplanets in the habitable zone, perhaps these worlds are not as common as we thought. Our surveys sample the most massive red dwarfs, because they're the brightest and easiest to study; but what if the titchy ones, about which we know relatively little, don't have habitable zone rocky exoplanets? [...]
It's even possible that the answer lies in several of these resolutions, which would allow the effect in any one area to be less pronounced. And we might be able to obtain confirmation soon. As our technology improves, for instance, we will be able to better see the lower-mass red dwarf stars, and look for planets in orbit around them.
Having done that, if we find rocky exoplanets, we can take a closer look at their potential habitability, determining if they orbit in the habitable zone, and if life there could have been stymied by stellar processes.
"Ultimately," Kipping wrote, "resolving the red sky paradox is of central interest to astrobiology and SETI, with implication as to which stars to dedicate our resources to, as well as asking a fundamental question about the nature and limits of life in the cosmos." (MORE - missing details)