When we look up into the starry sky at night, we only see a small portion of what's really up there. Red dwarfs comprise nearly 75% of all the stars in the Milky Way, yet they remain invisible to the naked eye. Given their predominance, astronomers and astrobiologists are keen to learn more about these small, cool stars, and their potential to host habitable planets. Now, new research from the Harvard-Smithsonian Center for Astrophysics has offered some clues, suggesting that as many as 6% of all red dwarfs host Earth-sized planets within their habitable zones — a calculation that brings the total number of red dwarf alien Earths across the galaxy to 4.5 billion.
Top image: Artist's impression of a sunset from the super-Earth Gliese 667Cc courtesy ESO/L.Calçada. The large sun is the red dwarf, 667C.