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.


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 Probabilities in the Galaxy

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The Autor - Klaus Piontzik