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Science 2 January 2004:
Vol. 303. no. 5654, pp. 59 - 62
DOI: 10.1126/science.1092322
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Reports

The Galactic Habitable Zone and the Age Distribution of Complex Life in the Milky Way

Charles H. Lineweaver,1,2* Yeshe Fenner,3* Brad K. Gibson3*

We modeled the evolution of the Milky Way Galaxy to trace the distribution in space and time of four prerequisites for complex life: the presence of a host star, enough heavy elements to form terrestrial planets, sufficient time for biological evolution, and an environment free of life-extinguishing supernovae. We identified the Galactic habitable zone (GHZ) as an annular region between 7 and 9 kiloparsecs from the Galactic center that widens with time and is composed of stars that formed between 8 and 4 billion years ago. This GHZ yields an age distribution for the complex life that may inhabit our Galaxy. We found that 75% of the stars in the GHZ are older than the Sun.

1 Department of Astrophysics, University of New South Wales (NSW), Sydney, NSW 2052, Australia.
2 Australian Centre for Astrobiology, Macquarie University, NSW 2109, Australia.
3 Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122, Australia.

* To whom correspondence should be addressed. E-mail: charley{at}bat.phys.unsw.edu.au (C.H.L.); yfenner{at}astro.swin.edu.au (Y.F.)

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Science. ISSN 0036-8075 (print), 1095-9203 (online)