Database numbering systems -- Used in an effort to reduce confusion in travel, a database with numbered items has been implemented, identifying various entities such as solar systems, individual planets, species, stars, etc.
M Class -- Inhabited planets, or planets meeting all standards to support complex humanoid life.
Technology Level -- Used to classify the stage of technology a planet is at. Classification is based upon the highest level found among all species inhabiting the world.    S *Highly advanced, unknown technology surpassing all current established sciences    A *Warp-capable    B *Sub-light travel    C *Rocket/Computing-capable    D *Industrial    E *Stone or earlier
This wouldn't let me edit the original post so here are the planetary classifications
Class A - Geothermal
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.
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.
Class C – Geoinactive
When all volcanic activity on a dClass A planet ceases, it is considered Class C. Essentially dead, these small worlds have cold, barren surfaces and possess no geological activity.
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.
Class E – Geoplastic
Class E Planets represent the earliest state 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.
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.
Class G - Geocrystalline
After the core of a Class F planet is sufficiently cool, volcanic activity lesses 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, M, N, O, or P class world.
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 are inhabited by humanoid populations. Most Class H worlds are hot and arid, but conditions can vary greatly.
Class I – Ice Giant
Also known as Uranian planets these gaseous giants have vastly different compositions from other giant worlds; the core is mostly rock and ice surround by 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.
Class J - Gas Giant
Class J planets are massive speheres of liquid and gaseous hydrogen, with small cores of metallic hydrogen. Their atmospheres are stremely turbulent, with wind speeds in the most sever storms reaching 600 kph. Many Class J planets also possess impressive ring systems, composed pirmarily of rock, dust, and ice. They form in the Cold Zone of a star system, though typically much closer than Class I Planets.
Class K – Adaptable
Through 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.
Class L – Marginal
Class L planets are typically rocky, forested worlds devoid of animal life. They are, however, well-suited for candidates for terraforming. Water is typically scarce, and if less that 20% of the surface is covered in water, the planet is considered Class H.
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 breathable oxygen-nitrogen atmosphere and temperate climate.
Class N – Reducing
Though frequently found in the Ecosphere, Class N planets are not conductive to life. The terrain is barren, with surface temperatures in excess of 500 degrees 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.
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.
Class P – Glaciated
Any planet whose surface is more that 80% frozen is considered Class P. Theses glaciated worlds are typically very cold, with temperatures rarely exceeding the freezing point. Though not prime conditions for life, hearty planets and animals are not uncommon.
Class Q – Variable
Theses 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, it is virtually impossible for life to exist on Class Q worlds.
Class R – Rogue
A Class R planet usually forms within a star system, but at some point in its evolution, the planet is expressed, 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.
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.
Class U – Gas Ultragiant
Class U 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.
Class X – Chthonian
Class X planets are the result of a failed Class U 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.
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, temperature are extreme, and atmospheric storms are amongst the most severe in the galaxy, with winds in excess of 500kph.