
Among the approximately earthgreat
planets there are still a number of planets which
have a mass of earth about the size of the earth
and which have a certain similarity to the earth
in the orbit time around their central star, as
well as in the rotation time. Such planets are
referred to here as approximately earthlike
planets. 
According
to the "Habitable Exoplanets Catalog" of September 2015, 4
out of 10 habitable planets about the
size of the earth can be described as distant earthlike.
This corresponds to a share of 40 %. The probability
factor is F_{a} = 0.4 = 2:5.
According to the "Habitable Exoplanets Catalog" of December
2017, 5 of 13 selected
habitable planets about the size of the Earth can be
described as distant earthlike.
This corresponds to a share of 38.4 %. The probability
factor is F_{a} = 0.384,615 = 5:13.
If you calculate the mean value from both information,
you get:

F_{gm} = 0.392,307
± 0.007
F_{gm} = 51:130 


2.5.1 Theorem 
39.23 % of all
habitable planets, in sunlike star
systems, are probably approximately
earthlike. 

hen equation 2.4.2 can be used to extrapolate a
relationship for approximately earthlike planets
Related to all star systems A in our
galaxy, the number N_{ha} of the solarlike star
systems, with habitable, approximately earthlike
planets, results to:
2.5.2 Equation 
N_{ha}
= N_{hg}
· F_{a}
N_{ha}=
A · F_{sph }·
F_{g }·
F_{a}
N_{ha}=
A · F_{s }·
F_{p }·
F_{h }·
F_{g }·
F_{a} 

Starting point are 100300 billion solar systems, in the
galaxy, and inserting into equation 2.5.2 provides:
2.5.3 Theorem 
There could be between 0.964
and 2.893 million approximately earthlike
habitable planets in solarlike star systems, in
our galaxy. 
The probability for habitable, approximately earthlike
planets, in solarlike star systems, in the galaxy, is
then:
2.5.4 Definition 
F_{ha}
= F_{hg}
· F_{a}
F_{ha}=
F_{sph }·
F_{g}
· F_{a}
F_{ha}=
F_{s }·
F_{p}
· F_{h }·
F_{g }·
F_{a} 
F_{ha} = F_{sph}·F_{g}·F_{a}
F_{ha}= 1:15,000 · 1,212:3,286 · 51:130
F_{ha}= 1:103,664
As a result, only about every 103,664th
sunlike star system produces a approximately earthlike
planet in the habitable zone.
