Scouting Out Life-Friendly Stars

Charles Lineweaver of the University of New South Wales in Australia and his colleagues modeled the evolution of our galaxy and analyzed the requirements for the so-called galactic habitable zone (GHZ). The team traced the distribution of four prerequisites for life: the presence of a host star, sufficient heavy metals to form terrestrial planets, enough time for biological evolution and a location that is safe from deadly supernovae. The findings, published today in the journal Science, indicate that the GHZ is a slowly spreading region located about 25,000 light-years from the galaxy's center. The stars encompassed by it formed between four billion and eight billion years ago; three quarters of them are a billion years older than the sun.