April 19, 2013
NASA’s Kepler planet-finding space telescope has discovered three “super Earths” orbiting in the habitable zone of two distant stars, including the one nearest the Earth in size yet discovered.
The planet designated Kepler-62f measures 40% larger than Earth, and is believed to have a rocky composition.
It and its larger, habitable-zone companion, Kepler-62e, orbit a star dimmer and older than the Sun called a K2 dwarf that is 1,200 light years from Earth in the constellation Lyra.
A third exoplanet — Kepler-69c — has been confirmed in the habitable zone of a Sun-like star in the constellation Cygnus some 2,700 light years from Earth.
It measures 70% larger than Earth, and has a 242-day orbit that approximates that of Venus.
“We know of only one star that hosts a planet with life — the Sun,” says Thomas Barclay, the Kepler scientist at the Bay Ares Environmental Research Institute in Sonoma, Calif., who was lead author on a Kepler-69 system paper published Thursday in the Astrophysical Journal. “Finding a planet in the habitable zone around a star like our Sun is a significant milestone toward finding truly Earth-like planets.”
But Barclay stresses that “we wouldn’t describe these as Earth-like planets ... We simply don’t know if other Earth-like planets are out there yet. We haven’t found any.”
To date Kepler has detected about 2,740 candidate exoplanets by measuring the extremely faint dip in starlight reaching its instruments when a planet passes in front of a star. Of those, 122 plus the seven total planets counted around Kepler-62 and -69 have been confirmed by other telescopes as true exoplanets.