Kepler-186 Earth-sized planet found in orbit, friendly to life
Scientists have found an Earth-sized world orbiting in a life-friendly zone around a distant star.
The discovery, announced on Thursday, is the closest scientists have come so far to finding a true Earth twin. The star, known as Kepler-186 and located about 500 light years away in the constellation Cygnus, is smaller and redder than the sun.
The star’s outermost planet, designated Kepler-186f, receives about one-third the radiation from its parent star as Earth gets from the sun, meaning that high noon on this world would be roughly akin to Earth an hour before sunset, said astronomer Thomas Barclay, with NASA’s Ames Research Center in Moffett Field, California.
The planet is the right distance from its host star for water — if any exists — to be liquid on the surface, a condition that scientists suspect is necessary for life.
NASA launched its Kepler space telescope in 2009 to search about 150,000 target stars for signs of any planets passing by, or transiting, relative to the telescope’s point of view. Kepler was sidelined by a positioning system failure last year.
Analysis of archived Kepler data continues. From Kepler’s observational perch, a planet about the size and location of Earth orbiting a sun-like star would blot out only about 80 to 100 photons out of every million as it transits.
The pattern is repeated every 365 days and at least three transits would be needed to rule out other possibilities, so the search takes time.
Scientists don’t know anything about the atmosphere of Kepler-186f, but it will be a target for future telescopes that can scan for telltale chemicals that may be linked to life.