Astronomers have discovered two alien planets around the same star whose orbits come so close together that each rises in the night sky of its sister world like an exotic full moon.
The newfound planets are 1,200 light-years from Earth and an unprecedented find, researchers said. They differ greatly in size and composition but come within just 1.2 million miles (1.9 million kilometers) of each other, closer than any other pair of planets known, according to a new study.
One of the newly discovered alien planets, called Kepler-36b, appears to be a rocky "super-Earth" 4.5 times as massive as our planet. The other, Kepler-36c, is a gaseous, Neptune-size world about eight times as massive as Earth. The two planets meet up every 97 days in a conjunction that would make each dramatically visible in the other's sky.
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