Complex life might require a very narrow habitable zone

Since the Kepler Space Telescope was launched into space, the number of known planets beyond the solar system (exoplanets) has grown exponentially. At present, 3,917 planets have been confirmed in 2,918 star systems, while 3,368 await confirmation. Of these, about 50 orbit within their star’s circumstellar habitable zone (aka the “Goldilocks Zone”), the distance at which liquid water can exist on a planet’s surface.