Earth-like planets orbiting small, cool stars may be common

Nature : At this week’s annual meeting of the American Astronomical Society in Long Beach, California, Courtney Dressing of Harvard University announced the results of a recent study of data from NASA’s Kepler space telescope. Dressing and colleagues have been focusing on M dwarfsâmdash;cool, low-mass stars that are abundant in our galaxy. Planets orbiting stars cannot be seen directly; they can only be surmised from the dimming of the star as the planet passes in front of it. The researchers estimated that 6% of the M dwarfs in Kepler‘s field of view could harbor Earth-like planets. It’s easier to look for planets orbiting M dwarfs than larger stars for two reasons. Because M dwarfs are relatively cool, their habitable zoneâmdash;the region where the temperature allows liquid water to exist on an orbiting planet’s surfaceâmdash;lies close to the star. Any Earth-like planets would then orbit multiple times per year rather than just once, thus providing astronomers more opportunity to study them. Also, because M dwarfs are relatively small, an Earth-like planet blocks a greater proportion of its star’s light, making it easier to detect.