Probabilities in the Galaxy
A Distribution Model for habitable Planets
Copyright © Klaus Piontzik

 German Version    
German Version    

1.6 - G-Stars with habitable Planets

habitable Zone

The habitable zone[9] is the distance range in which a planet must be located from its central star so that water can occur permanently in liquid form, as a prerequisite for life. The exact position of a habitable zone in a solar system depends on the star type, i.e. on the radiation and the temperature of the star. The habitable zone can, simplified, be calculated from the luminosity of a star. The average radius of this zone of any star can be calculated using the following equation:

Formula habitable Zone

d is the average radius of the habitable zone in AU
LStar is the bolometric luminosity of a star
LSun is the bolometric luminosity of the sun

In astronomy, bolometric brightness is a measure of the total luminosity of a celestial body, i. the luminosity integrated over the entire electromagnetic spectrum. With a star twice as bright as the sun, the average radius is 1.4 AU.

AU = astronomical unit = 149,597,870 Km = distance sun-earth

From 603 planetary systems observed by Kepler, planets in habitable zones could be detected in 10 systems. This corresponds to 1.658 % of the investigated planetary systems. The probability factor is therefore:

Fh = 0.016.58 = 10:603

Related to all star systems A in our galaxy, the number Nh of solar-like star systems with habitable planets results to:

1.6.1 Equation Nh = A Fs Fp Fh

Insert the factors into equation 1.6.1:

1.6.2 Theorem The number of solar-like star systems, with habitable planets, in our galaxy is probably 6.666 to 20 million.


 to previous page back home next  next page


A new version of the book is under construction. It will be published until April 2020
The new version will have 256 sites and it will be cheaper.
176 Sites
84 coloured Illustrations
9 Tables

Production und Publishing:
Books on Demand GmbH, Norderstedt

ISBN 9-783-7528-5524-1

Price: 22 Euro