NASA’s Kepler spacecraft has discovered two planets whose size and orbits make them the exoplanets, i.e. planets outside our solar system, most similar to Earth yet. Both planets are located 1,200 light-years from here, in the northern constellation Lyra. “Looming brightly in each other’s skies, the two planets circle their star at distances of 37 million and 65 million miles, about as far apart as Mercury and Venus in our solar system. Most significantly, their orbits place them both in the ‘Goldilocks’ zone of lukewarm temperatures suitable for liquid water, the crucial ingredient for Life as We Know It.”
What’s the Big Idea?
While the Kepler mission does not tell us which planets might be inhabitable by humans—due to their far proximity from Earth, reliable data on their composition is impossible to come by—the mission does inform us about the possible normalcy of planets like our own. “Kepler, launched in March 2009, hunts planets by staring at 150,000 stars in a patch of Milky Way sky, monitoring their brightnesses and looking for blips caused when planets pass in front of their home stars. To date the spacecraft has identified 115 planets and has a list of 2,740 other candidates.”