spacetoday.net: Astronomers plot galactic habitable zone

Posted: Fri, Jan 2, 2004, 6:06 PM ET (2306 GMT)
Astronomers have determined that up to one-tenth of the stars in the Milky Way galaxy lie in a habitable zone that would permit that to have planets that could harbor life. The research, by Australian astronomers and published in Friday's issue of the journal Science, determined that a ring-shaped habitable zone opened in the galaxy 25,000 light-years from its core eight billion years ago. The ring has since expanded and now includes stars as young as four billion years old. The zone's size and location is based on a number of factors, including the presence of heavy elements needed to form planets and stars located a safe distance from supernovae.