
Approximately earthgreat planets
are planets about the size of the earth with at
least one earth mass. Almost all planets of
approximately the size of the earth found so far
lie in a range of 1.3 to 4.8 earth masses. Most
of these planets are slightly larger than Earth,
or at most twice as large. 
According
to the "Habitable Exoplanets Catalog" of
September 2015, 10 of 31 habitable planets are about the
size of the earth. This corresponds to a share of 32.258
%. The probability factor is F_{g}
= 0.322,58 = 10:31.
According to the "Habitable Exoplanets Catalog"
of December 2017, 22 out of 53 habitable planets are
about the size of the earth. This corresponds to a share
of 41.509 %. The probability factor is F_{g}
= 0.415,094 = 22:53.
iIf you calculate the mean value from both information,
you get:

F_{gm} = 0.368,837 ±
0.046
F_{gm} =
1,212:3,286 


2.4.1 Theorem 
36.883% of all habitable
planets, in sunlike star systems, are probably
approximately earthgreat. 
Then, from equation 1.6.1 for solarlike star systems
that have habitable planets, a relationship can also be
extrapolated for approximately earthgreatplanets.
Related to all star systems A in our
galaxy, the number N_{hg} of solarlike star systems,
with habitable, approximately earthgreat planets,
results to:
2.4.2 Equation 
N_{hg}
= N_{h }·
F_{g}
N_{hg}=
A · F_{sph }·
F_{g}
N_{hg}=
A · F_{s }·
F_{p }·
F_{h}
· F_{g} 

Starting point are 100300 billion solar systems in the
galaxy. Insert into equation 2.4.2:
2.4.3 Theorem 
There could be 2.458 to 7.376
million, approximately earthgreat, habitable
planets in solarlike star systems, in the
galaxy. 
The probability for habitable planets, about the size of
the earth, in solarlike star systems, in the galaxy, is
then:
2.4.4 Definition 
F_{hg}
= F_{sph}
· F_{g} 
F_{hg} = F_{sph}·F_{g}
F_{hg}= 1:15,000 · 1,212:3,286
F_{hg}= 0.000,024,589 = 1:40,668
Among about 40,668 sunlike star systems
there is one, with at least one habitable, approximately
earthgreat planet.
