I’ve put off writing about Wesley Traub’s paper on the frequency
of planets in the habitable zone because I knew Adam Crowl had
reservations about Traub’s method. We talked about this at the
100 Year Starship Symposium, which led to Adam’s agreeing to
writing this piece for Centauri Dreams. How you define a
habitable zone is, of course, a critical matter, especially when
you’re dealing with a topic as compelling as extrasolar planets
that can support life. Adam places Traub’s work in the context
of earlier attempts at defining the habitable zone and finds HZ
estimates different from Traub’s, though one is surprisingly
similar to a much earlier study. by Adam Crowl The recent paper
by Wesley Traub [reference below] has estimated the frequency of
terrestrial (“Earth-like”) planets in the Habitable Zone (HZ) of
their stars based on statistical analysis of the recent Kepler
data release, but the frequency computed, of ~34(+/-14)% around
FGK stars, is dubious due to the assumption of wide HZ limits.
Before I discu