Life on Red Dwarf Stars

Factors Affecting the Likelihood of Life around Red Dwarf Stars

• Red dwarf systems are unlikely to be habitable due to low stellar flux, high probability of tidal locking, and small circumstellar habitable zones.

• The longevity and ubiquity of red dwarfs could provide ample opportunity for the possibility of habitability to be realized.

• Intense tidal heating caused by proximity to red dwarf stars is a major impediment to life developing in these systems.

• Extreme temperature differences created by one side of habitable-zone planets permanently facing the star, and the other perpetually turned away, reduces the probability of life around red dwarfs.

• The evolution of red dwarf stars would mean a zone where water was not liquid but in its gaseous state, rendering terrestrial planets uninhabitable.

• Tidal locking makes the planet rotate on its axis once every revolution around the star, creating great extremes of temperature.

• Climate models indicate that cloud formation on tidally locked planets would minimize the temperature difference between the day and the night side, greatly improving habitability prospects for red dwarf planets.

• Flares and star-spots experienced by red dwarfs could be very damaging for life, but if the planet had a magnetic field, it could deflect particles from the atmosphere.

• Red dwarfs account for about 85% of stars in the Milky Way, and there are expected to be tens of billions of super-Earth planets in the habitable zones of red dwarf stars in the Milky Way.

• Red dwarfs produce light energy for a very, very long time, and could exist for trillions of years, providing ample time for life to evolve and survive.

• Moons of gas giants within a habitable zone could overcome tidal locking issues since they would become tidally locked to their primary, not their star.

• The total amount of habitable zone around all red dwarfs combined is likely equal to the total amount around Sun-like stars given their ubiquity.Habitable Zone around Red Dwarf Stars

• Gliese 581 is a red dwarf star that could have liquid water at its terminator.

• Planets orbiting red dwarf stars can support an atmosphere due to their mass.

• In the future, red dwarfs may become blue dwarfs, which could allow for life to appear and evolve on previously frozen planets.

• Water retention is possible in the habitable zone of ultra-cool dwarfs, with a sweet spot in the 0.08 – 0.11 M⊙ range.

• Water worlds orbiting M-dwarfs could lose their oceans over time due to intense radiation environments.

• A second habitable zone could exist further out from the star where methane is liquid, allowing for methane-based life.

• Studies estimate that Earth-sized worlds are around 30-45% likely to exist around ultra-cool dwarf stars.

• TRAPPIST-1 (c. 0.084 M⊙) is likely to have planets similar in size to Earth.

• Fictional examples of aliens in red dwarf star systems exist.

• For more information, see the references and further reading sections.