Tidal Heating Shrinks Goldilocks Zone Around Red Dwarfs

scibri writes "An overlooked factor could shrink the habitable zone for planets around M-class dwarf stars by as much as 50%. For these smaller, cooler stars, the habitable zone was thought to extend to relatively close orbits. But as you get closer to a star, the tidal force it exerts on a planet increases. Since planets do not have perfectly circular orbits, tidal forces cause the planet to flex and unflex each time it moves closer to or further from its star; kneading its interior to produce massive quantities of frictional heat — enough to scour the planet of any liquid water. Because M-class dwarf stars are the most numerous in the galaxy, and close-in planets are easier to spot than more distant ones, such stars have been a major target for planet hunters seeking Earth-like worlds. But now it seems we may have been looking in the wrong place for Earth's twin."

Re:arguement should cut both ways

[bored_engineer]

In the context of red dwarfs, it's about distance. Gravity falls off with the square of the distance from the source. So, as the distance increases, the influence of the primary would fall off, thereby reducing the tidal heating. I suppose that it could heat a planet orbiting a brown dwarf, but a brown dwarf would have no (or little) emissions in the visible spectrum. Perhaps something besides terrestrial life could find it habitable, but I don't think we would be able to live there.

Re:Moons around large planets as well?

[justin12345]

You're confusing red dwarves with white dwarves. Red dwarves form small, white dwarves are the stellar cores of G type stars after they have blown off most of their mass during their red giant phase.