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So far, telescopes have been able to detect just over 300 planets outside our Solar System. Very few of these would be capable of supporting life, however. Most are gas giants like our Jupiter, and many orbit so close to their parent stars that any microbes would have to survive roasting temperatures.
But, based on the limited numbers of planets found so far, Dr Boss has estimated that each Sun-like star has on average one "Earth-like" planet. This simple calculation means there would be huge numbers capable of supporting life.
"Not only are they probably habitable but they probably are also going to be inhabited," Dr Boss told BBC News. (BBC News)