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“What we didn’t know five years ago is that perhaps 10 to 20 per cent of stars around us have Earth-size planets in the habitable zone…Describing their own estimates as “conservative,” the NASA planet hunters calculate that 100 million worlds within the Milky Way galaxy are able to sustain complex alien life forms. The estimate accounts for the 17 billion Earth-sized worlds scientists believe to be orbiting the galaxy’s 100 billion stars”

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(Source: aqqindex)