Red Dwarfs Could Sterilize Alien Worlds of Life

astroengine (1577233) writes "Red dwarf stars — the most common stars in the galaxy — bathe planets in their habitable zones with potentially deadly stellar winds, a finding that could have significant impacts on the prevalence of life beyond Earth, new research shows. About 70 percent of stars are red dwarfs, or M-type stars, which are cooler and smaller than the sun. Any red dwarf planets suitable for liquid water, therefore, would have to orbit much closer to their parent star than Earth circles the sun. That presents a problem for life — at least life as we know it on Earth, says physicist Ofer Cohen, with the Harvard-Smithsonian Center for Astrophysics. Cohen and colleagues used a computer model based on data from the sun's solar wind — a continuous stream of charged particles that permeates and defines the solar system –- to estimate the space environment around red dwarf stars. 'We find that the conditions are very extreme. If you move planets very close to the star, the force of this flow is very, very strong. Essentially it can strip the atmosphere of the planet unless the planet has a strong magnetic field or a thick atmosphere to start with,' Cohen told Discovery News."

Comments

Frist

[Blaskowicz]

I learned about that in Slashdot comments, really. Then reading articles on wikipedia, perhaps about specific stars, confirms that red dwarves are quite flare-y. At best the star may be relatively calm but then it will hurl cataclysmic bursts of crap at you anyway.

Re:Frist

[K. S. Kyosuke]

I don't think that is the only problem with red dwarves. The issue of tidal locking in the "habitable zone" (uhm), e.g., comes immediately to one's mind. The rather unfavorable spectrum doesn't help any either.

Re:Frist

[Immerman]

At planetary distances tidal locking is a relatively slow process dependent on the angular diameter of the planet as seen from the stellar core and the the magnitude of the gravitational force. Witness Mercury whose day is, after 4+ billion years in close orbit around a relatively massive star, still only 66% as long as its year.

Actually though tidal locking is not necessarily a problem - atmospheric models suggest that mixing would prevent the temperature imbalance from becoming too extreme. Of course you would end up with several very different ecological niches. Obviously photosynthesis would be impossible on the dark side, but that was a relatively late addition to the game on Earth, and there are plenty of other metabolisms available. Meanwhile the light side wouldn't have to deal with that pesky dark period, and the twilight zone would likely have pretty strong, steady winds from which life could potentially extract energy. Of course that's only relevant after complete locking - but then red dwarfs are essentially immortal, so as long as the planet manages to keeps its atmosphere life should have plenty of time to evolve to the conditions available.

The biggest problem I see with tidal locking is its potential impact on the magnetic field protecting the atmosphere, as it's believed that Venus and Mars have only tiny magnetic fields in large part because of slow currents in their cores.

Of course there's also the possibility of the moons of gas giants around red dwarfs. Thanks to the thermal emissions of the gas giant they could be at least a bit further from the sun, as well as getting significant protection from the gas giant's potentially much larger magnetic field. They would also have the benefit of tidally locking to the planet rather than the sun, so they would still experience a diurnal cycle, though it might be a bit slower than Earth's. Io for example orbits Jupiter in 1.7 days.

What indigenous life exists on red dwarf?

[Cryacin]

There's a species known as Felis Sapiens that evolved from Lister's cat.

Unfortunately they're down to one last surviving member due to a religious war based upon the colour of hats that were to be worn. He has no drive to procreate, as he is so perfect, that he is madly in love with himself. Meeeoowww.

Re:What indigenous life exists on red dwarf?

[AbsGeekNZ]

Red Dwarf, where we drink our gazpacho warm

Re: What indigenous life exists on red dwarf?

[dunkelfalke]

never heard of it?

Re:What indigenous life exists on red dwarf?

[stealth_finger]

There's a species known as Felis Sapiens that evolved from Lister's cat. . He has no drive to procreate, as he is so perfect, that he is madly in love with himself. Meeeoowww.

Pretty sure Kat has a desire to procreate, S-E-X I think I want it (comes across Lister's prone form) S-E-X I think I found it.

Not deadly forever

[mysidia]

See this article, on the subject, from back in 2009.

. Preliminary results from a dedicated research program have shown that planets around red dwarfs could be habitable if they can maintain a magnetic field for a few billion years ...

The high-energy radiation is predominantly emitted by young stars. As they age, red dwarfs become less magnetically active, while continuing to shine steadily at visible wavelengths for 100 billion years or more. ... ...

Therefore, if an orbiting planet can just hold onto its atmosphere through the wild early years of its red dwarf roommate, it could end up being a decent place to live.

Renaming

[bickerdyke]

Scientists might want to rethink the moniker "habitable zone" if it is filled with a deadly amount of stellar radiation... After all, the very definition of the habitable zone is based on the right amount of energy allow for liquid water reaching the planet...

Re:Renaming

[Roger W Moore]

Scientists might want to rethink the moniker "habitable zone" if it is filled with a deadly amount of stellar radiation...

The habitable zone only refers to the amount of heat radiation a planet receives it does not mean that every large rock there is habitable - just look at the moon. There are additional constraints for a habitable planet e.g. requires an atmosphere and liquid water. All this result does is to add an additional requirement near a red dwarf: you don't just need a gravitational field large enough to hold onto an atmosphere you also need a magnetic field to shield it.

Re:Renaming

[bickerdyke]

But isn't some radiation shielding not already part of the requirements?

Red Dwarf and radiation

[Rosco P. Coltrane]

Isn't it exactly how Rimmer and the entire crew died? Old news...

Re:Except...

[Immerman]

I think that's oversimplifying things. Models have shown that atmospheric mixing would result in far less extreme temperature differences than you would naively expect. Meanwhile you don't need light for life, photosynthesis is believed to be a relatively late addition to the metabolic game after all, so the dark side could be a thriving ecosystem with chemovores on the bottom, while the light side and twilight region could incorporate photosynthesis as well.

In fact tidal locking could potentially increase the habitable zone considerably - move the planet closer to the sun and the dark side becomes warmer and more hospitable while the light side becomes increasingly scorching. Conversely move it further from the sun and the dark side becomes more frigid, but the light side becomes milder. So long as things don't become so cold that you freeze out the atmosphere on the dark side, or so hot that even the dark side can't support liquid water, you have the potential for life.

And of course tidal locking to something as far away as a star is a slow process dependent on the absolute gravitational force and the angular size as viewed from the center of the primary - and the second tends to be dramatically smaller for planets than for moons.