This Earth-sized planet, known as Kepler-186f, is the first to be found within the so-called Goldilocks (not too hot, not too cold Juuuust nice) or habitable zone, where the conditions are just right in terms of the balance between atmospheric pressure and temperature for water to exist as a liquid.
Although it has been estimated that at least 40 billion Earth-sized planets orbit within the Milky Way, this discovery was the needle in the haystack that seems to indicate that Earth may not be unique.
Also known is the fact that four other planets also orbit its star. Should the star prove to be similar in terms of size and properties to our own sun, it becomes increasingly likely that life could be found on the planet.
“We know of just one planet where life exists – Earth. When we search for life outside our solar system we focus on finding planets with characteristics that mimic that of Earth,” said Elisa Quintana, research scientist at the SETI Institute at NASA’s Ames Research Center in Moffett Field, Calif., and lead author of the paper published today in the journal Science. “Finding a habitable zone planet comparable to Earth in size is a major step forward.”
Unfortunately, the star it orbits is only half the mass of our sun and the planet would only receive a third of the energy that we receive from our own sun. Further, its orbit takes about 130 days, about a third of ours.