"aquablue" wrote in message ...
the reason I ask is: marcy says that she estimates that 12% of sun like
stars would have a similar solar system arangement to ours -- thus may have
capacity for earth like planets harboring life.

That's about right, according to all the estimates I've seen
(which have ranged from 10-12%). The percentage may be
higher because large portions of the Milky Way are blocked
from our view, and because we currently have somewhat
myopic definitions of "sun-like stars" and "earth-like planets".

Rick