Can life exists on planets around red dwarf stars?

[John Clark]

Our sun is brighter than every star you can see in the night sky with your naked eye and yet the sun is brighter than 80% of the stars in the universe, that's because most stars are red dwarfs but I have long thought that life could not develop on any planet orbiting such a star. Proxima Centauri is a red dwarf, it has 12.2% the mass of the sun but gives off 588 times less heat, that's why although its the closest star to us it's far too dim to be observed with the naked eye. Any planet around a star as dim as Proxima Centauri would have to be 24 times closer to its sun than the Earth is to ours to be at the same liquid water loving temperature. A planet that close would be gravitationally locked so one side continuously faced the sun and the other side would never see it, so either mega-hurricane force winds would continuously sweep the planet's surface or one side would be far too hot to support life and the other side so cold the atmosphere with freeze out. And that's not even the worst.  

Outside the fusion producing core of our sun is a several hundred thousand mile thick radiation transfer zone, in this zone there is very little movement of matter, the temperature decreases only very slowly, and the primary method of transferring energy is smoothly made through radiation. Outside the radiation zone is a several hundred thousand mile thick convection zone where there are lots of plops and bubbles and movement of hot matter that transfers energy up to the surface in an irregular way.  It is the movement in the convection zone that causes magnetic fields which causes sunspots and solar flares. In red dwarfs there is no radiation zone, the convection zone reaches all the way down to the center of the star, so although red dwarfs are much dimmer than the sun they have solar flares that are hundreds or thousands of times as intense as the suns, and such evil dwarfs produce more life destroying X-rays too.  Because the planet is so close to the red dwarf the situation is made even worse. So although the planet may have the right temperature for liquid water I doubt if it actually has any because any water in its upper atmosphere would be blasted apart by the intense solar wind into free hydrogen and oxygen, and unless it was as massive as Jupiter it would not be able to hold onto its hydrogen. So regardless of how wet it started out, after a few million years it would be bone dry. 

And now researchers have proposed yet another reason why life is unlikely to develop around red dwarfs. We've never found a planet in the habitable zone around a red dwarf that also had a Jupiter type gas giant planet, and without that you can't have an asteroid belt, and without astroids an earth wannabe would have no way to receive water like the earth did during the Late Heavy Bombardment.

Life on Exoplanets In the Habitable Zone of M-Dwarfs?

John K Clark    See what's on my new list at  Extropolis

lhb

[Lawrence Crowell]

I saw the same paper. I have seen gravitational tidal locking as big obstacles to the idea of life on a planet around an M-class star. Even if there is an annular region, where the star would appear on the horizon, such that temperatures are in principle comparable to Earth's temperature the winds would be horrific. The temperature gradient there would result in tremendous winds. Stellar systems of planets around M-class stars lacking a Jovian type planet is new to me. However. one thing I have not heard mentioned is these planetary systems, say the Trappist one, has a half dozen planet orbit in a small region. They would gravitationally perturb each other much more than planets do in this solar system. That could lead to long term instabilities of orbits.

LC