Astronomers have long assumed they’d have to look far and wide and deep into our galaxy before they found a single Earth-like planet. But now it looks like there may be many – quite nearby, perhaps as close as 13 light years – virtually in our own cosmic backyard. Working with data from NASA’s Kepler mission, scientists at the Harvard-Smithsonian Center for Astrophysics have calculated that every 6 in 100 red dwarf stars should have at least one Earth-sized world orbiting in the so-called habitable zone where liquid water can exist. Red dwarfs are the most common type of star. They’re much cooler, a thousand times dimmer, and generally only about one third the size of our Sun. So, if you look up at night, your unaided eye won’t see a single one. For every star you can see, there are at least 3 red dwarfs, which you can’t. But the Kepler telescope and other research instruments easily can. It's almost as if the Universe wants us to discover these worlds: Earth-sized planets are larger, relative to the dwarfs they orbit than they would be to Sun-like stars. So they produce a much stronger light curve - in other words a bigger dips in brightness for Kepler to more easily notice. And even better, because red dwarfs are cooler than our Sun, the Goldilocks Zone, where temperatures are “just right” for life, is much closer in to the stars – which means a year on these speculative planets is much shorter than our year – which means it takes Kepler less time to see multiple passes of these planets and thus confirm their existence. But perhaps most intriguing, red dwarfs have life spans much longer than our Sun. So scientists speculate we might come across life on planets around red dwarfs that is much older that life as we know it on Earth. For SPACE.com, I'm Dave Brody