In distant galaxies exist stars that are smaller and cooler than our own Sun. These so-called red dwarf or M dwarf stars also live 10 times as long as stars like ours and are the most numerous in our galaxy, outnumbering stars like ours 10 to 1. Because of their longevity and quantity, they have become a prime target for the constantly evolving search for life outside our planet.
However, there are a few things about these solar systems that may make it difficult for water, the primary indicator of habitability, to exist. Some planets in these systems reside very close to red dwarf stars and rotate with them in synchronicity. This casts one side of these exoplanets into perpetual, icy darkness, never seeing the sun's light, while the other side of the globe is continuously exposed to the red dwarf’s scorching heat. From what we know about the habitability of the one planet we know supports life — Earth — balance is key, and it’s unlikely the harsh climates of either side of these planets would give way to the conditions necessary to sustain life.
