Take the most common type of star in the Milky Way — so-called red dwarf stars that are cooler, smaller and longer-lived than stars like the sun.
Then, survey a sampling for orbiting planets and extrapolate the results. What do you get?
A stunning claim that 40 percent of our galaxy’s 160 billion red dwarf stars have plus-sized Earths orbiting the right distance for liquid water to exist on their surfaces, a condition believed to be necessary for life.
Full Story: ‘Billions’ of habitable worlds in our own Milky Way galaxy?