Planetary Classification
A planet is a celestial body in orbit around a star or stellar remnants, that has sufficient mass for
self-gravity and is nearly spherical in shape.  A planet must not share its orbital region with other
bodies of significant size (except for its own satellites), and must be below the threshold for
thermonuclear fusion of deuterium.    

If a celestial body meets those requirements, it is considered a planet; at that point, the planet is
further classified by its atmosphere and surface conditions into one of twenty-two categories.
Class A planets are very small, barren
worlds rife with volcanic activity.  This
activity traps carbon dioxide in the
atmosphere and keeps temperatures
on Class A planets very hot, no matter
the location in a star system.  When
the volcanic activity ceases, the
planet "dies" and is then considered a
Class C planet.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

0-2 billion years old
1,000 - 10,000 km
Hot Zone/Ecosphere/Cold Zone
Partially molten, very hot
Carbon dioxide, hydrogen
Cools to become Class C
None
Gothos
Class A - Geothermal
Class B - Geomorteus
Class B planets are generally small
worlds located within a star system's
Hot Zone.  Highly unsuited for
humanoid life, Class B planets have
thin atmospheres composed primarily
of helium and sodium.  The surface is
molten and highly unstable;
temperatures range from 450° in the
daylight, to nearly -200° at night.  No
life forms have ever been observed on
Class B planetoids.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

0-10 billion years old
1,000 - 10,000 km
Hot Zone
Partially molten
Extremely tenuous
N/A
None
Mercury, Nebhilum
Class C - Geoinactive
When all volcanic activity on a Class A
planet ceases, it is considered Class C.
 Essentially dead, these small worlds
have cold, barren surfaces and
possess no geological activity.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years old
1,000 - 10,000 km
Hot Zone/Ecosphere/Cold Zone
Barren
None
N/A
None
Psi 2000
Class D - Dwarf
Also known as Plutonian objects,
these tiny worlds are composed
primarily of ice and are generally not
considered true planets.  Many moons
and asteroids are considered Class D,
as are the larger objects in a star
system's Kuiper Belt.  Most are not
suitable for humanoid life, though
many can be colonized via pressure
domes.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years old
100 - 4,000 km
Hot Zone/Ecosphere/Cold Zone
Barren and cratered
None or very tenuous
N/A
None
Pluto, Ceres, Eredas-Il
Class E - Geoplastic
Class E planets represent the earliest
stage in the evolution of a habitable
planet.  The core and crust is
completely molten, making the planets
susceptible to solar winds and
radiation and subject to extremely
high surface temperatures.  The
atmosphere is very thin, composed of
hydrogen and helium.  As the surface  
cools, the core and crust begin to
harden, and the planet evolves into a
Class F world.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

0-2 billion years old
10,000 - 15,000 km
Ecosphere
Molten, high surface temp.
Hydrogen compounds
Cools to become Class F
Carbon cycle
Excalbia
Class F - Geometallic
A Class E planet makes the transition
to Class F once the crust and core
have begun to harden.  Volcanic
activity is also commonplace on Class F
worlds; the steam expelled from
volcanic eruptions eventually
condenses into water, giving rise to
shallow seas in which simple bacteria
thrive.  When the planet's core is
sufficiently cool, the volcanic activity
ceases and the planet is considered
Class G.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

1-3 billion years old
10,000 - 15,000 km
Ecosphere
Volcanic, barren
Carbon dioxide, ammonia, methane
Cools to become Class G
Bacteria
Janus IV
Class G - Geocrystalline
After the core of a Class F planet is
sufficiently cool, volcanic activity
lessens and the planet is considered
Class G.  Oxygen and nitrogen are
present in some abundance in the
atmosphere, giving rise to increasingly
complex organisms such as primitive
vegetation like algae, and animals
similar to sponges and jellyfish.  As the
surface cools, a Class G planet can
evolve into a Class H, K, L, M, N, O, or
P class world.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

3-4 billion years old
10,000 - 15,000 km
Ecosphere
Rocky, mostly barren
Carbon dioxide, oxygen, nitrogen
Cools to Class H, K, L, M, N O, P
Vegetation, simple organisms
Delta Vega
Class H - Desert
A planet is considered Class H if less
than 20% of its surface is water.  
Though many Class H worlds are
covered in sand, it is not required to
be considered a desert; it must,
however, receive little in the way of
precipitation.  Drought-resistant
plants and animals are common on
Class H worlds, and many are
inhabited by humanoid populations.  
Most Class H worlds are hot and arid,
but conditions can vary greatly.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

4-10 billion years old
8,000 - 15,000 km
Ecosphere
Hot, arid; >20% surface water
Oxygen, nitrogen, argon, metals
N/A
Drought-resistant plants/animals
Dimovius, Nimbus III, Corneria,
Ocampa
Class I - Ice Giant (Uranian)
Also known as Uranian planets, these
gaseous giants have vastly different
compositions from other giant worlds;
the core is mostly rock and ice
surrounded by a tenuous layers of
methane, water, and ammonia.  
Additionally, the magnetic field is
sharply inclined to the axis of
rotation.  Class I planets typically form
on the fringe of a star system.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years old
30,000 - 100,000 km
Cold Zone
Rock, ice, methane, ammonia
Hydrogen, helium
N/A
None
Uranus, Neptune, Q'tahL
Class J - Gas Giant (Jovian)
Class J planets are massive spheres of
liquid and gaseous hydrogen, with
small cores of metallic hydrogen.  
Their atmospheres are extremely
turbulent, with wind speeds in the
most severe storms reaching 600 kph.
Many Class J planets also possess
impressive ring systems, composed
primarily of rock, dust, and ice.  They
form in the Cold Zone of a star
system, though typically much closer
than Class I planets.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years old
50,000 - 500,000 km
Cold Zone
Liquid metallic hydrogen
Hydrogen, helium
N/A
None
Jupiter, Saturn
Class K - Adaptable
Though similar in appearance to Class
H worlds, Class K planets lack the
robust atmosphere of their desert
counterparts.  Though rare, primitive
single-celled organisms have been
known to exist, though more complex
life never evolves.  Humanoid
colonization is, however, possible
through the use of pressure domes
and in some cases, terraforming.  

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

4-10 billion years old
5,000 - 10,000 km
Ecosphere
Barren, little surface water
Thin, mostly carbon dioxide
N/A
Primitive single-cell organisms
Mars, Mudd
Class L - Marginal
Class L planets are typically rocky,
forested worlds devoid of animal life.  
They are, however, well-suited for
humanoid colonization and are prime
candidates for terraforming.  Water is
typically scarce, and if less than 20%
of the surface is covered in water,
the planet is considered Class H.  

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

4-10 billion years
10,000-15,000 km
Ecosphere
Rocky; little surface water
Argon, oxygen, trace elements
N/A
Limited to vegetation
Alarin III, Ciden II, Indri VII
Class M - Terrestrial
Class M planets are robust and varied
worlds composed primarily of silicate
rocks, and are highly suited for
humanoid life. To be considered Class
M, between 20% and 80% of the
surface must be covered in water; it
must have a breathable oxygen-
nitrogen atmosphere and temperate
climate.  

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

10,000-15,000 km
Ecosphere
Abundant surface water;
temperate climate
Nitrogen, oxygen, argon,
N/A
Vegetation, animal, & humanoid
Earth, Cardassia, Kalidar, Vulcan
Class N - Reducing
Though frequently found in the
Ecosphere, Class N planets are not
conducive to life.  The terrain is
barren, with surface temperatures in
excess of 500° and an atmospheric
pressure more than 90 times that
of a Class-M world.  Additionally, the
atmosphere is very dense and
composed of carbon dioxide; water
exists only in the form of
thick,vaporous clouds that shroud
most of the planet.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

3-10 billion years
10,000-15,000 km
Ecosphere
Barren; high temperatures
carbon dioxide and sulfides
N/A
None
Venus
Class O - Pelagic
Any planet with more than 80% of the
surface covered in water is
considered Class O.  These worlds are
usually very warm and possess vast
cetacean populations in addition to
tropical vegetation and animal life.  
Though rare, humanoid populations
have also formed on Class O planets.  

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

3-10 billion years
10,000-15,000 km
Ecosphere
80% water, archipelagos
Nitrogen, oxygen, argon
N/A
Cetacean, humanoid, animal
Azati Prime, Ka'Tula Prime, Zirat
Class P - Glaciated
Any planet whose surface is more
than 80% frozen is considered Class P.  
These glaciated worlds are typically
very cold, with temperatures rarely
exceeding the freezing point.  Though
not prime conditions for life, hearty
plants and animals are not uncommon,
and some species, such as the Aenar
and the Andorians, have evolved on
Class P worlds.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

3-10 billion years
10,000-15,000 km
Ecosphere
80% frozen water, cold
Nitrogen, oxygen
N/A
Vegetation, animal, & humanoid
Andoria, Exo III, Rebena Te Ra,
Rura Penthe
Class Q - Variable
These rare planetoids typically
develop with a highly eccentric orbit,
or near stars with a variable output.  
As such, conditions on the planet's
surface are widely varied.  Deserts
and rain forests exist within a few
kilometers of each other, while
glaciers can simultaneously lie very
near the equator.  Given the constant
instability, is virtually impossible for
life to exist on Class-Q worlds

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years
4,000-15,000 km
Hot Zone/Ecosphere/Cold Zone
Molten, frozen, jungle, etc
Very tenuous to very dense
N/A
None
Genesis Planet
Class R - Rogue
A Class R planet usually forms within a
star system, but at some point in its
evolution, the planet is expelled,
likely the result of a catastrophic
asteroid impact.  The shift radically
changes the planet's evolution; many
planets merely die, but geologically
active planets can sustain a habitable
surface via volcanic outgassing and
geothermal venting.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years
4,000-15,000 km
Interstellar space
Temperate
Primarily volcanic outgassing
N/A
Non-photosynthetic plants, animals
Dakala, Veneihm, Founders'
Homeworld (prior to 2371)
Class S - Gas Supergiant
Aside from their immense size, Class S
planets are very similar to their Class J
counterparts, with liquid metallic
hydrogen cores surrounded by a
hydrogen and helium atmosphere.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years
500,000-100,000,000 km
Cold Zone
Liquid metallic hydrogen
Hydrogen and helium
N/A
None
Tethe-Alla IV
Class U - Gas Ultragiant
Class T planets represent the upper
limits of planetary masses.  Most exist
within a star system's Cold Zone and
are very similar to Class S and J
planets.  However, Class T planets
occasionally form within a star
system's Hot Zone.  If they are
sufficiently massive (13 times more
massive than Jupiter), deuterium
ignites nuclear fusion within the core,
and the planet becomes a red dwarf
star, creating a binary star system.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years
50,000,000 - 120,000,000 km
Hot Zone/Cold Zone
Liquid hydrogen, deuterium
Hydrogen and helium
Can evolve into red dwarf stars
None
Diadem, Tethe-Alla V
Class X - Chthonian
Class X planets are the result of a
failed Class T planet in a star system's
Hot Zone.  Instead of becoming a gas
giant or red dwarf star, a Class X
planet was stripped of its hydrogen/
helium atmosphere.  The result is a
small, barren world similar to a Class B
planet, but with no atmosphere and
an extremely dense, metal-rich core.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years
1,000-10,000 km
Hot Zone
Barren, extremely hot
None
N/A
None
Osirus
Class Y - Demon
Perhaps the most environmentally
unfriendly planets in the galaxy,
Class Y planets are toxic to life in
every way imaginable.  The
atmosphere is saturated with toxic
radiation, temperatures are extreme,
and atmospheric storms are amongst
the most severe in the galaxy, with
winds in excess of 500 kph.

AGE
DIAMETER
LOCATION
SUFRACE
ATMOSPHERE
EVOLUTION
LIFE FORMS
EXAMPLES

2-10 billion years
10,000-15,000 km
Hot Zone
Barren; extremely hot
Turbulent, with toxic radiation
N/A
Mimetic
Planet Hell (Delta Quadrant)