Abstract
Simple heuristic models and recent numerical simulations show that the probability of habitable planet formation increases with stellar mass. We combine those results with the distribution of main-sequence stellar masses to obtain the distribution of stars most likely to possess habitable planets as a function of stellar lifetime. We then impose the self-selection condition that intelligent observers can only find themselves around a star with a lifetime greater than the time required for that observer to have evolved, T i. This allows us to obtain the stellar timescale number distribution for a given value of T i. Our results show that for habitable planets with a civilization that evolved at time T i = 4.5 Gyr the median stellar lifetime is 13 Gyr, corresponding approximately to a stellar type of G5, with two-thirds of the stars having lifetimes between 7 and 30 Gyr, corresponding approximately to spectral types G0–K5. For other values of T i the median stellar lifetime changes by less than 50%. Key Words: Astrobiology—Bioastronomy—Complex life—Extraterrestrial life—SETI. Astrobiology 9, 617–621.
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