The Archurion Nebula is one of the "Eternal Realms," a collection of the Ambrosia Galaxy's three largest nebulae, each spanning three thousand light-years in diameter. It is located near the absolute center of the Endless Horizon and contains around 2,400,000 star systems, as well as serving as the birthplace to innumerable sapient species and civilizations.
The Archurion Nebula stands as one of the most notable and important celestial objects across the whole of the Ambrosia Galaxy. Serving as one of the three "Eternal Realms" the Archurion Nebula has been both the setting and the prize of countless conflicts waged across its massive amethyst borders, with civilizations ranging from the Etymology of ancient times, to more recent superpowers such as the Ambrosia Alliance of United Systems. The reason why the nebula is coveted by many is due to numerous reasons, ranging from the overall quality of her worlds' in terms of resource and habitability, to the many Thavmiums found only within her borders and nowhere else in the Ambrosia Galaxy.
Along with being long sought by outside forces, the Archurion Nebula has also served as the cradle of some of Ambrosia's greatest and largest civilizations to ever arise. The most notable would be the Theogony, who arose from within her borders and would soon expand their empire to most of the known galaxy, as well as numerous others, a trait it shares with its two-sisters.
Like each member of the Eternal Realms, the Archurion Nebula is absolutely massive, spanning a mind-boggling three thousand light-years in diameter, making it easily visible from outside of Ambrosia's respective galactic borders, appearing like a massive violet mist in a sea of amaranth starlight.
Due to its massive size, it remains unknown as to how exactly the Archurion Nebula formed, as well as how old the nebula is, as no known form of dating has been able to reveal any definitive age of the structure, traits also shared by each member of the Eternal Realms. As a result, it is believed by most that Archurion and its sister nebulae formed at the exact moment the galaxy itself did.
The layout of Archurion is fairly standard when comparing it to other, less impressive nebulae within the Ambrosia Galaxy, appearing like a typical H II region, albeit on a massive scale. The gasses that make up the nebula continually grow more dispersed the further outward from the center one goes, eventually until' the normal galactic dust overtakes it, While the more inward you are, the thicker and more compact the cosmic gas of the nebula becomes, so much so that nearly all of Ambrosia's normal galactic dust is completely overtaken by its own respective dust.
The hue of the nebula's gasses also depends as to where one is located. Towards the centermost sections of the nebula, the violet hue of the nebula starts to become more blue in coloration. While at the edges of the nebula, a pricing violet color is experienced. In-between these two extremes, an almost heliotrope color of lighter purple is created due to the two different mediums mixing together.
At the center of the Archurion Nebula lies a large globular cluster of stars, containing around ninety-five thousand and eleven stars closely bound together by extremely strong gravities (due to the large masses involved). Within this region, many bright stars are located, such as A-Class main sequence stars, giving the star cluster an overall bright orange coloring from outside of its borders, leading some astronomers to speculate that the Archurion Nebula may have once been a small dwarf galaxy. While only accounting for around four percent of the stars within the nebula, a large amount of species to arise from within Archurion have came from worlds located inside of the star cluster, allowing them to progress through the typical technological stages much quicker then those located on more isolated stars. Surprisingly, there are very little high-mass stars in the cluster.
Surrounding the star cluster, millions of independent stars are located all throughout the nebula's structure. These stars can range from anything from brown dwarves and sub brown dwarves, to more impressive stellar masses such as blue, yellow or red hypergiants, O type stars and even neutron stars and black holes. It is within the outer regions of the nebula do most of the newer star formations occur, as there is less gravitational influence caused by nearby stars that may otherwise prevent a protostar from completely finishing formation. In small areas in the outer layers, small open star clusters have formed due to some stars entering within each other's gravity's, forming small barycenter star communities, though these only have maximum star population of around a hundred separate stellar members.
It is also here where the high mass stars we would expect to find in such a stellar nursery occur. So far, 74 high-mass O type stars have been discovered around the outer regions of the nebula, most of which are tightly grouped with other high-mass stars.. A Luminous Blue Variable can also be found and is one of the brightest stars in the nebula, 15 Wolf-Rayet stars can also be found, 12 of which belong to small clusters and associations, typical of WRs.
Due to the Archurion Nebula's massive size, the entire view from within the nebula gives off a vibrantly violet effect, overtaking the normally amaranth hue the Ambrosia Galaxy's galactic arms give off, making it appear as if one is in a completely different galaxy. Due to this, several species located deep within the Archurion Nebula would not actually know the galaxy's true coloring until' they reached the technological capabilities to leave the nebula, giving most a realization of how much lager the greater Ambrosia Galaxy is compared to their realm of origin.
Affectionately referred to as the "Violet Effect," the effect given off will vary depending on how far within the nebula one is, with the violet coloring obviously becoming much more apparent from deeper into the nebula's center, while if one was at the outer fringes of the nebula, the normal Ambrosia coloring can be made out interspliced with the violet from the nebula.
Porphyrion Stars stand as one of the most notable features of the Archurion Nebula, as they are only found from within their borders with one known exception. They are extremely hot stars believed to have been formed entirely, or nearly entirely from the Amethysttium that makes up their realm of origin, giving them a distinctive violet-coloring, making them at odds from most typical colors a star can naturally take. Due to being only found from within the Ambrosia Galaxy, the Porphyrion Stars are member of the "Thavastéri," a classification of anomalous types of stars found nowhere else in the Local Universe. Despite being exclusive to the Archurion Nebula, the Porphyrion Stars are very few in number, with only around fifty known Porphyrion Stars in existence.
They give off an extreme amount of heat due to the hyperactive nature of the respective gasses that they have formed from. with the hottest Porphyrion Star known giving off a massive one million, two hundred and forty degree Celsius, while colder ones clock in at a temperature of around six hundred thousand degrees Celsius. causing nearly every celestial body to be in orbit around said Porphyrion Star to be bathed in massive amounts of heat and solar radiation. As a result, only worlds located far from their parent Porphyrion Stars have a chance of developing most common forms of life, however due to this extreme heat, many Porphyrion Star systems are home to more exotic lifeforms.
As they are extremely hot, most Porphyrion stars are very small and very dense, in order to not completely explode from being very bright. A usual low-mass Porphyrion star usually only has a radius of about 50,000 km, comparable to the very smallest red dwarfs and the very largest white dwarfs. However, its luminosity would be comparable to that of a blue hypergiant, shining 800,000 times more than the Sun, similar to extreme WO stars. Porphyrion stars also have their own spectral class on the MK system - the P class. (P stands for porphyrion, obviously)