|If one assumes
that other star systems, with non sun-like stars, have the
same or similar planetary frequency, then equation 7.1.1
can be modified in such a way that it applies to any star
FX is the probability for the occurrence of a set
of stars that have a certain property, namely the spectral class.
A = 200 300 billion is
the number of stars
in the galaxy.
This concept can be applied to all stars for which
observational data are available .
Looking at the planets, an equation for the probability
of a habitable planet, in any system, can be set up:
Fph = 201:14,000 · 10:603 = 1:4,200
Among 4,200 star systems is one that possesses planets
and among them at least one habitable planet exists.
Then for the set of all systems Nphx of a spectral class with
planets and at least one in the habitable zone:
For the set of all solar systems NphxGal in the galaxy, with planets
and at least one in the habitable zone:
= ∑ Nphx
The following applies:
= ∑ Nphx = ∑ (A·FX·Fp·Fh)
Since A remains the same
for all spectral classes, A can be drawn from the sum:
= ∑ Nphx = A·∑ (FX·Fp·Fh)
a first assumption that Fp and Fh remain the same
for all spectral classes, they can also be drawn from the
= ∑ Nphx ≈ A·Fp·Fh·∑
sum over all spectral classes (for the probabilities FX) yields the
entirety of the stars in the galaxy, so:
It is thus a
= ∑ Nphx
||The amount of all star
systems, in the galaxy, with planets and at least
one in the habitable zone, is 47.619 to 71.428
It is important here that all factors can be determined
empirically by appropriate instruments of observation.