Life in our Galaxy

For advanced life to evolve on a planet in the Milky Way, that planet can be neither too near nor too far from the galactic center. It has to be far enough from the center to avoid being affected by the supernova explosions that regularly occur there. On the other hand, such a planet would probably need many elements heavier than hydrogen and helium to produce molecules with diverse biological functions; these heavier elements are most abundant toward the center of the galaxy.

The Sun is about 26,000 light-years from the center of the Milky Way, about halfway out. In 2004, a team led by Charles Lineweaver at the University of New South Wales in Sydney showed that advanced life could only evolve in a ring between 22,000 and 30,000 light-years from the center of the galaxy, just 10 percent of the total area of the Milky Way.