Earth-like worlds may be closer and more plentiful than anyone imagined.
Astronomers reported Wednesday that the closest Earth-like planet may be just 13 light years away. That planet hasn't been found yet, but should be there based on the team's study of red dwarf stars. Galactically speaking, it's a stroll across the park.
"We now know the rate of occurrence of habitable planets around the most common stars in our galaxy," said study co-author David Charbonneau. "That rate implies that it will be significantly easier to search for life beyond the solar system than we previously thought."
Small, cool red dwarfs are the most common stars in our galaxy, numbering 75 billion.
Despite their dimness, these stars are good places to look for Earth-like planets, according to a release. Red dwarfs make up three out of every four stars in our galaxy for a total of at least 75 billion. The signal of a transiting planet is larger since the star itself is smaller, so an Earth-sized world blocks more of the star's disk. And since a planet has to orbit a cool star closer in order to be in the habitable zone, it's more likely to transit from our point of view.
The Harvard-Smithsonian Center for Astrophysics team estimates 6 percent of red dwarf stars have Earth-like planets. To qualify, the planet must be roughly the size of Earth and get as much light from its star, as Earth does from the sun.
This high rate of occurrence should simplify the search for extraterrestrial life.
The authors of the study say locating nearby, Earth-like worlds may require a dedicated small space telescope, or a large network of ground-based telescopes.
"You don't need an Earth clone to have life," said Harvard astronomer and lead author Courtney Dressing.
The three habitable-zone planetary candidates identified in this study are Kepler Object of Interest (KOI) 1422.02, which is 90 percent the size of Earth in a 20-day orbit; KOI 2626.01, 1.4 times the size of Earth in a 38-day orbit; and KOI 854.01, 1.7 times the size of Earth in a 56-day orbit. All three are located about 300 to 600 light-years away and orbit stars with temperatures between 5,700 and 5,900 degrees Fahrenheit. (For comparison, our Sun's surface is 10,000 degrees F.)
These results will be published in The Astrophysical Journal.