NASA researchers have published confirmation this week that the Kepler mission will be able to reveal the presence of Earth-sized planets around Sun-like stars. The mission’s first scientific results appear today in the journal Science.
Lead author William Borucki, of NASA Ames Research Center in Moffett Field, California, and his colleagues announced that Kepler has detected the giant extrasolar planet HAT-P-7b, one of the roughly two dozen exoplanets that have been discovered by ground-based observations and the CoRoT mission as they “transited” in front of their stars, periodically dimming the starlight.
Many more exoplanets — more than 300 now — have been detected by the so-called “wobble” or radial velocity method, where a planet’s gravitational tug influences the motion of its star.
HAT-P-7b is comparable to Jupiter in size and orbits a star analogous to our Sun. It showed up in 10 days’ worth of Kepler data on the intensity of light from over 50,000 stars.
“The detection of the occultation without systematic error correction demonstrates that Kepler is operating at the level required to detect Earth-size planets,” the authors write.
The $500 million Kepler mission launched in March 2009 and will spend three and a half years surveying more than 100,000 sun-like stars in Cygnus-Lyra.
By staring at one large patch of sky for the duration of its lifetime, Kepler will be able to watch planets periodically transit their stars over multiple cycles, allowing astronomers to confirm the presence of planets and use the Hubble and Spitzer space telescopes, along with ground-based telescopes, to characterize their atmospheres and orbits. Earth-size planets in habitable zones would theoretically take about a year to complete one orbit, so Kepler will monitor those stars for at least three years to confirm the planets‘ presence.
Astronomers estimate that if even one percent of stars host Earth-like planets, there would be a million Earths in the Milky Way alone. If that’s true, hundreds of Earths should exist in Kepler’s target population of 100,000 stars.