NASA's Kepler Space Telescope detected an Earth-like planet circling a neighbouring star in our galaxy's Goldilocks zone. Kepler-186f is located in the Cygnus constellation around 500 light-years from Earth. The habitable zone, also known as the Goldilocks zone, is the region of space around a star where planetary-mass objects with sufficient atmospheric pressure can support liquid water on their surfaces. While it is estimated that there are at least 40 billion Earth-sized planets surrounding our Milky Way Galaxy, this is the first Earth-sized planet identified in another star's habitable zone. In addition to Kepler-186f, the Kepler-186f system contains four more planets that orbit a neighbouring star. This indicates that if the planet's neighbouring star is similar to our Sun, the possibility of life on this planet increases enormously. "We know of only one planet on which life may exist - Earth." "When we seek for life outside our solar system, we focus on finding planets with traits similar to Earth," said Elisa Quintana, research scientist at NASA's Ames Research Center in Moffett Field, Calif., and main author of the work published in the journal Science. "Discovering a habitable zone planet the size of Earth is a significant breakthrough." Kepler-186f's nearby star has half the mass and size of our solar system's Sun and receives only one-third of the energy that we do. Kepler-186f orbits its star every 130 days.