PiMath.de Probabilities in the Galaxy
for Life, Intelligence und Cvilization

A Distribution Model

Klaus Piontzik

 German Version    
German Version    

1.8 - Planet Categories

The Planetary Habitability Laboratory (PHL) is a research project by the University of Puerto Rico at Arecibo with the aim of estimating the habitability of the solar system and exoplanets.

A classification of planets emerged from this project. First, the star orbit is divided into three zones: warm, habitable and cold. Planets are divided into two types of rock planets (terrestrial) and gas giants (Jovian).

The following PHL size classes exist:

Mini earths (mini terrans) are about Mercury in size, up to 0.4 earth radii and up to 0.1 earth masses.

Subearthes (subterrans) are about the size of Mars, between 0.1 and 0.5 earth radii and 0.4 to 0.8 earth masses

Planets with a size of 0.8 to 1.5 earth radii and 0.5 to 5 earth masses are called earth-like (terrans). In this system, the earth can be classified as a warm terran.

Super earths (Superterrans) have a radius between 1.5 and 2.5 earth radii and the mass is 5 to 10 times the earth.

The Neptune-like planets (Neptunians) are approximately Neptune in size and have a mass of 10 to 50 Earth masses and are 2.5 to 6 times the size of the Earth.

All celestial bodies that are about Jupiter size or larger are classified as Jupiter-like (Jovians).

There are several catalogs for exoplanets or habitable planets. The next chapter mainly deals with the data from the "Habitable Exoplanets Catalog", as well as the classification of planets according to the "Planetary Habitability Laboratory".

According to the PHL size classes, there is a planet category that is called “earth-like” (Terrans). In the model presented here, this planet category is classified as approximately terran great.

Terrans = Terran great

In addition, two further subcategories are created, the distant earth-like planets (Terran like) and the "Earth 2" (Terran earth).

The exact description and definition of the new categories is dealt with in the next chapter.


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