Planetary classification

Planetary classification is a scheme for classifying planets according to mass, surface, and composition.

It is estimated that there are 820 billion planets in the orbiting 180 billion stars, corresponding to the average of 4.55 planets per star. Based on the probability of being shut out in baseball scoring 4.55 runs per game, 95% of all stars would have planets. There are ~524 billion terrestrial planets (639‰) and ~296 billion giant planets (361‰) in the. There are nearly 4000 known planets as of 2018, which is five billionth of all planets in our galaxy.

Mass
Planetary mass classification is the classification of s by. The mass ranges from 1 to 13 es. This classification uses the letter codes in order of decreasing mass. There are three broad types of planets by mass: -mass planet (class J), -mass planet (class N), and -mass planet (class E) with subclasses a (super-), b (mid-) and c (sub-) in order of decreasing mass.

s are non-stellar objects that revolve around s including the that have suitable mass range that s without fusing  in their cores. Brown dwarf (hyperjovian) and dwarf planet (hypoterrestrial) were originally included. It was removed because these are not planets. Brown dwarf is not considered a planet because they are massive enough to fuse deuterium in their core, somewhat like stars, and dwarf planet because it is not massive enough to clear the neighborhood.

Of all known non- planets, super-Jupiters are most abundant despite it is the rarest mass class of planet in the galaxy due to the fact that super-Jupiters are most easily detected. Midplanets are the most common type of known planets overall. There are only few dozen known mid-Earths and sub-Earths due to difficulties in detecting them. Mid-Earth is the Milky Way's most abundant mass class of planet with sub-Earth close behind. Planets massing less than 20 M$⊕$ make up about 73% of all planets with remainder 27% are more massive than 20 M$⊕$.

Orbit
Planetary orbit classification is the planet classification according to their orbital distance from the parent star.

Surface
Planetary surface classification is the classification of planets about what's on the surface, such as deserts, forests, and oceans. More than one surface class can be identified for one planet.

Composition
This scheme is about what the planet is dominantly made of, such as carbon, methane, or water. Like the surface classification, more than one composition class can be identified for one planet, albeit more rarely.