
In previous
observations, star systems with a sunlike
central star were examined. Assuming that other
star systems, i.e. not solarlike systems, also
have frequencies for technological civilizations,
then the DrakeSeager equation 10.3.2 can be
derived: 


12.1.1 Equation 
N_{X}
= A · F_{X}
· F_{ph }·
F_{k}
· F_{Liz} 
Equation 12.1.1 then applies to the star quantities
formed by a solar type or spectral class[1],
respectively.

The suns of
our galaxy are represented in the socalled
HertzsprungRussel diagram[2], arranged according
to colour and luminosity. A total of 13
spectral types exist.
The spectral types O, B, A, F, K,
i.e. the blue, the bluewhite, white, the
whiteyellow and the orange spectral colors make
up about 1% of the total stars.
In addition, there are the brown dwarfs and the
red giants, i.e. the spectral classes L,
T, Y, R, N, S, which also make up 1%
of the total stars.
Two classes have become known so far. This is the
set of sunlike G stars, with a
yellow spectral color and the probability F_{s}
= 0.28 = 7:25.
As well as the number of red dwarfs, i.e. M
stars with a redorange spectral color and a
probability F_{RZ}
= 0.7 = 7:10. Thus, the two spectral
classes make up 98 % of the
total stars in the galaxy. 
