A Home in the Milky Way

What fraction of
stars in our Galaxy
might play host
to planets that
can support multicellular
life?
Lineweaver et al.
calculate
the probable extent
of hospitable
space for complex life in the Galaxy, called the Galactic
habitable zone (GHZ). Their criteria include distance
from deadly supernovae, enough heavy elements to
form terrestrial planets, and enough time for life to
evolve. Based on these criteria, the GHZ is an annular
region between 7 to 9 kiloparsecs from the Galactic center
and contains about 10% of the Milky Way stars with
ages between 4 to 8 billion years old.