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Red dwarfs have wider habitable zones than we thought?

From Centauri Dreams:

Widening the Red Dwarf Habitable Zone

A new paper has revised our estimates of how wide the habitable zone would be around a red dwarf star.  This comes from taking into account the difference in spectrum between a red dwarf and a Sunlike star.  Compared to the Sun, red dwarfs give off a higher percentage of their EM radiation in longer wavelengths like red and infrared, wavelengths that aren’t reflected as much by snow and ice as shorter wavelengths are.  So while in our system, a planet covered in snow and ice would reflect a lot of heat back into space and thus reinforce its own freezing (runaway glaciation), in a red-dwarf system it would retain a higher percentage of the star’s heat and could stay unfrozen at a larger proportional distance than we’d thought.  This could make red-dwarf habitable zones 10-30 percent wider than we thought, and increase the potential number of habitable planets around them.  Sure, those HZs are pretty narrow to begin with, but red dwarfs constitute maybe 70-80 percent of the galaxy’s stars, so it adds up.

Be sure to read the comments.  There’s a lot of interesting discussion about other factors that would go into habitability around a red dwarf.  It’s a lively and ever-evolving subject in astrophysics today.

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