Before The Purge, there were about 10 million planets that could naturally maintain life. These planets were scattered all throughout the galaxy with the highest concentration of them being in the first three districts closest to the center of the galaxy. These three districts were referred to as 'The Rings of Life' as together they contained about half of the galaxy's habitable planets. District 10, the farthest from the center, had less than 300 worlds and was often called 'The Abyss'.
After The Purge, the number of livable planets diminished greatly. 20% of the planets were destroyed completely, leaving nothing but asteroid fields and space dust in their gravity wells. Another 65% were transformed from abundant life-giving orbs, to barren wastelands covered with scars acquired from orbital bombardment. Some of these wastelands were unlivable, while others contained survivors, though many of the survivors died during the first years after The Purge. In total, The Purge was responsible for the destruction or mutilation of 85% of the Biiractan's survivable terrains. The first decades after the tragedy were spent rebuilding communications between star systems and trying to figure out how many had actually survived.
Planets are divided into 4 classes, and 3 sizes.
(Size 1) Dwarf: A planet with a diameter of 11,ooo km or less. These planets are low gravity worlds that are home to many of the galaxy's smaller and shorter sentient races. They account for about 15% of the Biiractan's inhabitable planets (Pre-Purge).
(Size 2) Average: An average planet has a diameter between 12,000 and 15,000 km. Most livable worlds (80% Pre-Purge) in the galaxy fall in the average category (hence the name) and galactic time measurements are derived from these category of planets. Some planets that are not part of the Union use their own measurements for things like time and weight.
(Size 3) Giant: If a planet is 16,000 km in diameter or greater, it is considered a giant. Giant planets are high gravity and species originating on giant planets often need specialized pressure suits when traveling through space or onto different worlds. In the same way, people visiting from an average size or dwarf planet need special accommodations when traveling to a giant planet.
Planets classes have to do with atmosphere type.
Class 1: The most common life-supporting planets in the Biiractan galaxy are Average Class 1 planets, which have been given the nickname 'normal' planets. Class 1 planets have atmospheres that are mostly made up of Nitrogen and Oxygen, which most species in the galaxy can breathe comfortably in, although this nitrogen / oxygen combination is poisonous to some species, requiring them to wear breathing apparatuses when out of their native atmosphere.
Class 2: The second most common atmosphere type seen in the galaxy is a blend of Nitrogen, Carbon Dioxide, and Oxygen. Class 2 planets are normally covered in dense vegetation often having trees that reach up taller than city skyscrapers. It is not rare to find eco-cities built into the natural tree structures. The vegetation is so dense and the trees so tall, that the greenery can be seen from space.
Class 3: Planet's with Class 3 atmospheres usually contain little to no vegetation. Only certain species of plants and animals can survive in the Methane/Helium gas that comprises a Class 3 atmosphere. Many native's of Class three planets are experts in building underground cities, since the atmosphere's are harsh and not ideal for surface living. Class three planets account for about 12% of hospitable worlds in the Biiractan.
Class 4: The smallest number of inhabitable atmosphere's belong in Class 4. These atmospheres are comprised of a wide array of different gases and often micro-metallic substances. There are only three different species of sentient life that can survive naturally in these conditions. Other organics come to these planets for harvesting the precious metals that are often found below the brutally toxic clouds.
Gas Giants in the Biiractan are not part of the class or size system because they're not ideal for civilization and most go ignored although a few have been discovered that have valuable resources, however the exploration of such planets is dangerous and expensive. Many independent pioneers seeking to find their fortune by discovering a valuable resource on such planets often never return from their expeditions.
