Extrasolar Planets - A General Introduction - Exoplaneten.de - The Exoplanet Directory

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Classes of Exoplanets

Extrasolar Planets

September 2015


Exoplanets are so diverse that it is difficult to find a universal and convincing classification. Many authors use a classification based on the mass of the object, its distance to the central star and the temperature range derived therefrom as well as the presumed composition. This results in names such as hot jupiter-like planet, mini-Neptune, ocean planet, Earth-like planet, and many more. However, this classification has the disadvantage that it anticipates too many assumed properties and forces the objects into a highly simplified grid. This is well exemplified by 51 Pegasi b: This planet is often referred to as "hot Jupiter," but what similarities actually exist between 51 Pegasi b and the planet we know as Jupiter? One is an already well-measured gas giant in the colder zones of our solar system, the other is an object of similar mass, but in terms of size, composition and weather phenomena, it should be drastically different from Jupiter because 51 Pegasi b receives so much more energy from its star than Jupiter does from the Sun.


On this website, the above-mentioned terms are used as well. They are now standard practice in the literature and must not be missing in a serious presentation. The presentation of ​​the planets, however, is based on their distance from Earth, starting with the nearest objects. It should be borne in mind that the distance indications extend in all three spatial directions. Two planets, which are 500 light years away from Earth, are not necessarily in direct neighborhood, but can be 1,000 light years apart in extreme cases.

The following categories of extrasolar planets are mentioned in the literature:

Jupiter-like planets and "Super-Jovians"
"Hot Jupiters"
Neptune-like planets
"Mini-Neptunes"
"Super-Earths"
Terrestrial or "Earth-like" planets"
Terrestrial ocean planets

Rogue planets


 
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