Astrobiology Workshop, Macquarie University July 12-13 2001

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The Age Distribution of Terrestrial Planets in the Universe :

Charles Lineweaver (University of New South Wales)

Using a straight-forward but novel combination of the most recent observations of the metallicities of extrasolar planet host stars, the star formation rate and the metallicity evolution of the Universe I obtain an age distribution for terrestrial planets in the Universe. Three-quarters of the earth-like planets in the Universe are older than the Earth. Their average age is 1.8 +/- 0.9 billion years older than the Earth. If life forms readily on earth-like planets -- as suggested by the rapid appearance of life on Earth -- this analysis gives us an age distribution for life on such planets and a rare clue about how we compare to other life which may inhabit the Universe. I will be updating this research result which is now in press at Icarus. (see also astro-ph/0012399)