Scientists have so far detected at least 550 planets outside the solar system – and another 2,000-plus await confirmation. But how to pick out the ones that may be Earth-like havens for life? Here's what one team looks for in assessing any planet's potential habitability and its similarity to Earth's properties.
Planets in the habitable zones of a certain kind of star smaller than the sun might show key signatures of life in their atmospheres but actually be lifeless.
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