Speculation on this point has been ongoing since humanity's realization that other stars existed . Only in the past year, however, have answers and discoveries been realized. The above plot summarizes the four known cases of normal stars having planets. The later two cases were discovered by astronomers led by Geoff Marcy and Paul Butler as part of a greater project inspecting 120 stars for orbiting planets. Interestingly enough, the planets around the later two stars have temperatures in the right range to allow liquid water - and hence may have conditions ripe for the development of life .
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