With the launch of NASA's Kepler Mission next year, scientists hope to find Earth-size planets in the habitable zone of far away stars:
The search for life beyond Earth is the search for a good place to live, a habitable planet, in orbit about a long-lived star where life may arise and evolve. The first place we looked was at stars like our own Sun, a middle-sized, middle-aged star. G-Stars like the Sun are stable for about 10 billion years, which is a good long time for planets to form, and life to evolve. We also expected to find solar systems like our own with small terrestrial planets near the star, and larger gaseous planets farther out. This particular pre-conception was discarded with the discovery of hot Jupiters on 4-day orbits about their stars.
The idea that other, less-massive, dimmer stars than the Sun could also host habitable worlds has long been debated. A particular class, M-Stars, are of interest simply because there are so many of them-they are the most common star in the galaxy. They're the cool stars that inhabit our neighborhood.
There's considerable interest in the question of whether M-Stars could host habitable planets. Would the planets be tidally locked with one face always directed toward the M-Star? Would flares wipe out life on the local planet? If M-Stars could host habitable planets, life may be much more widespread that we've previously thought. Thus, M-Stars are of interest to astrobiologists including SETI scientists who are searching for life beyond Earth.