The Delvi Star System

((Unless stated, all images displayed on this world are made by me, Chrispy_0))

Article Contents

The Delvi System consists of one star (Fevaultar), four rocky inner planets (Tula, Collena, Sephar, Senon), and five gaseous outer planets. Rather typical of any star system of this type. The system is unique for having 3 planets that are within the habitable zone, that can also fully support life, and for having a double planet with stable orbits. All three planets have developed life independently of each other. There is a fourth world, a moon of Baultar, that has developed a fourth form of life independently. Only Collena developed Sentient life. The Regalti Species lives here, and they have created an interplanetary civilization with over a hundred billion people. They live almost entirely in space, and have mostly abandoned their original homeworld of Collena.
  Author's Note
is a symbol indicating the measurement is in reference to the Sun. 1M for example means 1 solar Mass, meaning it is equal to the mass of the Sun. In this respect, I have several other symbols to indicate other measurements. E Indicates the measurement is in reference to the Earth. C indicates the measurement is in reference to the planent Collena. J indicates the measurement is in reference to Jupiter. This is to make the numbers easier to understand instead of using very large numbers or an excessive number of exponents.
In the Cairn Sector , 400 light-years from the center.

  • 115 Billion Regalti
  • 1.2 Billion Vusinor
  • 354 million Maorians
  • 1 Billion from other sentient species
  • Fevaultar

    Mass: 1.05 M
    Radius: 1.11 R
    Rotational Period: 26 Edays
    Surface Temperature: 5914K
    Composition: 72.9% Hydrogen, 25.72% Helium, 1.38% Other

    Fevaultar is the largest object in the Delvi system, comprising over 99% of the system's mass. It is a high metallicity white-yellow dwarf star, and is 4.75 billion Eyears old. It is expected to live another 4.5 billion years before it swells into a red giant, swallowing Tula and Collena-Sephar, before it ultimately collapses into a White dwarf.

    Fevaultar is a unique star in that it has three planets within its habitable zone, and all three planets around Fevaultar (Collena, Sephar, Senon) are planets that can support life. Usually all these planets would have been sterilized by a large asteroid impact or gamma ray burst, or their atmospheres would be just a little too thick or thin, or the planets would have been just a little too large or small, or their parent star itself would have had an outburst of radiation that would have fried the atmospheres. There are too many factors to count. The Devli System in this regard, has managed to stay incredibly stable.

    For comparison, the Sun is a very similar star in terms of size, composition, and age to Fevaultar. The Vusinor Venjint system also has a similar star. The only difference is that Fevaultar is slightly brighter, larger, and more massive. These three systems share many similarities, such as habitable worlds, an asteroid belt separating inner, rocky planets, from outer, gaseous ones, and having a shell of comets surrounding it in a giant cloud stretching a trillion kilometers away.
    The Sun by NASA/SDO (AIA)
    Fevaultar looks very similar to this image of the sun, and if there was any difference at all, it would be slightly whiter and brighter, otherwise an image of the sun wouldn't be that distinguishable from an image of Fevaultar, or any other yellow dwarf star.


    Mass: 0.155 ME
    Radius: 3365 km
    Density: 5.81 g/cm^3
    Surface Temperature: 147*C
    Surface Gravity: 0.55 earth
    Escape Velocity: 6.07 km/s
    Speed: 44 km/s
    Distance: 0.48au (71,962,000km)
    Rotational Period: 36 Edays
    Orbital Period: 119E
    Obliquity: 7.3 degrees
    Composition: 52% Iron, 48% Silicates
    by Chrispy_0
    Tula is an extremely dense, extremely hot planet. It is the closest orbiting body to Fevaultar and is one of the densest objects in the star system (not including the cores of the gas giants or the core of Fevaultar itself). The Planet has been continuously mined for raw materials for building in space for almost four centuries, and is expected to last another few hundred thousand years before the mass of the planet is completed converted for ships and space habitats. Most of the materials are being used to construct a sort of Dyson Swarm where the vast majority of the Regalti in this system live.

    Collena and Sephar

    by Chrispy_0
    by Chrispy_0

    While Sephar is often called Collena's Moon, the two are infact a double planet, orbiting each other around a barycenter well away from the surface of either world. (For the purposes of this page, Collena is considered the planet, and its orbital information is in respect to the star, and Sephar is considered a moon, and its orbital information is in respect to the barycenter around which both planets orbit.)

    Sephar has a much denser elemental composition than Collena and it is speculated that it was once much cloer to the sun, that changed its position in the early history of this star system. Collena and Sephar possibly even collided, then ended up orbiting each other. Both planets have substantial hydrospheres. and are able to easily support life. Regalti live on both worlds and both are considered their home worlds.


    Mass: 0.995 ME
    Radius: 6,948 km
    Density: 4.24 g/cm^3
    Surface Temperature: 13.2*C
    Surface Gravity: 0.842 earth
    Escape Velocity: 10.7 km/s
    Speed: 27.1 km/s
    Distance: 1.26au (188,000,000km)
    Rotational Period: 28 Ehours (1 Cday)
    Orbital Period: 498 Edays (414 CDays)
    Obliquity: 22.2 degrees
    Composition: 25.05% Iron, 73.5% Silicates, 1.45% other

    Map: Link
    Population: 1 Billion


    Mass: 0.28 ME
    Radius: 3,507km
    Density: 9.28 g/cm^3
    Surface Temperature: 14.9*C
    Surface Gravity: 0.92 earth, 9.09 m/s^2
    Escape Velocity: 7.98 km/s
    Speed: 0.953 km/s (orbiting Collena)
    Distance: 512,529 km (from Collena)
    Rotational Period: 19.3 Ehours
    Orbital Period: 30.33333 Edays (26 Cdays)
    Obliquity: 22.2 degrees
    Composition: 32.9% Iron, 66.1% silicates, 1% other

    Map: (Work in Progress)
    Population: 800 million


    Mass: 1.1 ME
    Radius: 6557km
    Density: 5.55g/cm^3
    Surface Temperature: 19.7*C
    Surface Gravity: 1.04 earth
    Escape Velocity: 11.6 km/s
    Speed: 20.7 km/s
    Distance: 326,811,750 km
    Rotational Period: 38.4 Ehours
    Orbital Period: 3.15 Eyears
    Obliquity: 28.9 dgrees
    Composition: 21.7% Iron, 78.1% silicates, 0.2% other

    Population: About 500 Million

    Third planet from Fevaultar, Senon is a planet with a dense, oxygen rich atmosphere. Despite being much more distant to the star than Collena, Senon is currently a warmer world, though it has had frequent stretches of ice ages. Senon has three moons, each a tenth of the mass of the planet. They orbit in a 1:1, 2:1, and 4:1 resonance with Senon, creating periodic surges of oceanic tides.

    by Chrispy_0
    Life independently evolved on Senon, Collena, and Sephar at the same time. On Senon, the large ice ages regularly wiped out land based life, but the thick atmosphere guarantees that when the ice ages end, the planet warms quickly and life surges back on land. There's almost a dozen separate instances of sea life crawling out of the ocean and evolving lungs or other forms of respiration. About half of these occurences came from a fish-like ancestor, one of them involved larvae forms of coral crawling on land, then rooting in the ground and turning into giant coral trees. The other five instances found were from arthropods.

    Currently the planet is at the end of its last ice age cycle, which lasted almost twenty million years. The Regalti found vast swaths of empty fertile land when they first explored the world. It was settled but because this was just as the Exodus from Collena was starting, most Regalti stayed in space instead of settling a new planet. the population never reached more than half a billion people, and today, large swaths of the planet are currently used to support the hundred billion people living in space with food and animal products. Most of the planet remains undeveloped and unexplored.

    Senon's Moons




    Closest moon to Senon with a rotational period of 15 days. It is icy, and has a subterranean ocean. It is lifeless. The ocean water, though salty, is quite pure, and the entire moon is designated as a reservoir for the Regalti living in space. It is estimated that with proper recycling, the moon can supply over five million years worth of water to trillions of people. This moon is tidally locked with Senon.


    Middle moon of Senon with a rotational period of 30 days. It is a rocky world with no atmosphere and a large iron core. Its pristine white surface is ruined in many parts by craters and still active volcanoes, which remain active due to tidal forces between Atar, Senon, and the other two moons.


    Farthest moon of Senon with a rotational period of 60 days. It is a dark, red, sandy world that is no longer volcanically active. It has no atmosphere, but possibly did in the distant past. This world was thought to be able to support life, but after centuries of searching, none was ever found.


    Mass: 3.56 MJ
    Radius: 84,361 km
    Density: 2.7 g/cm^3
    Surface Temperature: -170*C
    Surface Gravity: 6.49 earth
    Escape Velocity: 104 km/s
    Speed: 11.7 km/s
    Distance: 6.75au
    Rotational Period: 14 Ehours
    Orbital Period: 17 Eyears
    Obliquity: 10 degrees
    Composition: 86% hydrogen, 6% Helium, 6% Chlorine, 2% other

    Fourth planet from Fevaultar, and comprising a large chunk of the mass that isn't part of Felvater, Baultar is the largest planet in the system and is large enough to have an influence on every other object in the system, including the star. It has thick bands of chlorine gas, hydrogen and helium. It has an extremely powerful magnetic field that reaches past the orbit of the 5th planet from Fevaultar, Kinta, and the 6th planet Mintar. Its position in the star system is quite important as far as life on Collena, Sephar, and Senon are concerned, as well as the numerous space habitats, because Baultar tends to alter the orbits of asteroids and comets away from these worlds.

    Baultar by Chrispy_0
    This planet has over 30 moons, including one that is nearly as large as Collena, three that are larger than Sephar, and three more that are larger than Tula. These moons are almost entirely icy water worlds, too far from Fevaultar to recieve any warmth, or are smaller, rockier, captured asteroids. Two are volcanic hellscapes, being torn apart by tidal forces between Baultar and the moons. There is one more moon, where an alternate form of biochemistry was discovered that uses a number of exotic elements. It is entirely single celled, and is not studied due to the extremely corrosive aspects of the world.

    Baultar's Major Moons




    Largest moon of Baultar, it is nearly the size of Collena. This world is mainly composed of rock, though it does have a significant amount of ice. Around half of this ice is water, and the other half is various forms of frozen acids. Water isn't harvested from this world generally, but the amount of frozen acids that can safely be extracted has contributed greatly to the Regalti's industrial developements in space.


    Second largest moon of Baultar, it is 50% the size of Collena. This moon has a thick atmosphere made of Hydrochloric Acid. Its oceans are made of Florine, water, and Nitric Acid. It's main crust composition is various compounds of sulphur. The world is all around acidic and highly reactive, even explosive, with itself. Tidal forces, combined with the thick atmosphere keep the world warm enough for all these elements to remain in liquid and gaseous states.

    How anything can form life here without dissolving isn't beyond Regalti science, but they make no attempt to study it. Most attempts to land a probe results in the probe melting into a torrent of liquid before it ever reaches the surface, so studies are done from orbit with imaging systems.


    Third largest moon of Baultar. It is one of the closer moons to the planet. As a result, this planet is one of the volcanic hellscapes, being ripped apart by tidal forces. It has by far the most active volcanism in the Delvi system. Huge pieces of crust regularly shatter off the world and break apart, turning into a temporary ring around Baultar as it eventually burns the planet's atmosphere. Cevaultar is rapidly shrinking as a result, and it is estimated the moon will no longer exist in about another hundred thousand years.


    Mass: 24 ME
    Radius: 26,642 km
    Density: 1.81 g/cm^3
    Surface Temperature: -194*C
    Surface Gravity: 1.37 earth
    Escape Velocity: 26.8 km/s
    Speed: 9.17 km/s
    Distance: 11.1 au
    Rotational Period: 12.2 Ehours
    Orbital Period: 36 Eyears
    Obliquity: 3 degree
    Composition: 70% Hydrogen, 28% Iron, 2% other elements

    Fifth Planet from Fevaultar, Kinta is a deceptively low mass gas giant that appears to be quite normal. Its mass isn't anything to write about, especially for a gas giant. It's almost entirely composed of hydrogen, but has an extremely massive Iron core for its size. The interactions between the iron core and the metallic hydrogen just above, combined with solar wind and its placement in Baultar's magnetic field, gives it especially powerful magnetic storms. Normally they appear to be green in color, but have been observed being every other color, sometimes disappearing only to be emitting in a different spectrum of light. Most gas giants have never ending auroras in some way, but none as intense as seen on this world.

    In the past, these magnetic storms have been so powerful, the planet has sometimes appeared as a bright green dot in the sky from Collena, even during the day, and has also been observed to be every other color.
    Kinta globe by Chrispy_0


    Mass: 1.1 MJ
    Radius: 69,384 km
    Density: 1.49 g/cm^3
    Surface Temperature: -212*C
    Surface Gravity: 2.95 earth
    Escape Velocity: 63.4 km/s
    Speed: 8 km/s
    Distance: 14.6 au
    Rotational Period: 8.8 Ehours
    Orbital Period: 54.8 years
    Obliquity: 36 degree
    Composition: 90% Hydrogen, 2% Methane, 2% Ammonia, 2% Water, 2% other elements

    Sixth Planet from Fevaultar, Mintar would be quite the impressive planet...if it weren't in the same system as Baultar. This planet does have one of the larger ring systems among the gas giants of the system, but there are much more impressive examples elsewhere. The specific composition of this planet makes it appear violet, and its rings are very bright. Very much like Baultar, Mintar influences everything near its orbit, including the other planets. It has 23 moons, including several that are larger than Sephar and Tula.
    by Chrispy_0


    Mass: 18 ME
    Radius: 26,709 km
    Density: 1.35 g/cm^3
    Surface Temperature: -214*C
    Surface Gravity: 1.03 earth
    Escape Velocity: 23.2 km/s
    Speed: 7.13 km/s
    Distance: 18.4 au
    Rotational Period: 21 Ehours
    Orbital Period: 77.6 years
    Obliquity: 63 degree
    Composition: 80% Hydrogen, 10% Helium, 5% Water, 3% Methane, 2% other elements

    Second to last planet from Fevaultar, Halana is an "Ice Giant". It is primarily composed of Hydrogen and Helium, but also a significant amount of water and methane, giving it its blue appearance. It has 13 moons.

    The Vusinor have a significant presence in the Devli system, but only specifically around Halana. They paid the Regalti for the mining rights to several of Halana's moons, and harvesting rights to Halana itself. They use the planet Halana as a Switchboard World to allow for instant communication across their empire. They gave the Regalti access to roughly 25% of the network capability of the planet, which is far, far more bandwidth than the Regalti's current population can take advantage of.


    Mass: 3 ME
    Radius: 17,703 km (3998 km not including atmosphere)
    Density: 0.918 g/cm^3
    Surface Temperature: -223*C
    Surface Gravity: 0.4 earth
    Escape Velocity: 12 km/s
    Speed: 5.69 km/s
    Distance: 28.8 au
    Rotational Period: 8.8 Ehours
    Orbital Period: 152 years
    Obliquity: 26.3 degree
    Composition: 25% Helium, 25% Hydrogen, 20% Nitrogen, 15% Iron, 5% Silicates, 5% Water, 3% Methane, 2% other elements

    Arta is the furthest planet from Fevaultar. It is the coldest planet, and has the longest orbital period. This planet is known to the Regalti as the Idanthi World, which the closest translation to English is "Marshmallow".

    For a long time, Sceintists were baffled by this world because it had the composition of a rocky terrestial world, an icy world, and a gas giant. Theories were finally put forth that thought the world was formed as an inner planet early in the system's history, but was smashed by another world and sent it flying into the outer edges of the system. It's orbit eventually stabilized, after absorbing several planetary masses worth of gases, which gave the planet the strange composition it has today.
    by Chrispy_0
    The Planet's atmosphere is 2.4 ME in size, while the planet itself is only 0.6 ME in size. The inner world is almost never visible, covered in a thick cloud of Nitrogen and Water, the outer radius of this layer almost three times as large as the planet. Swirling clouds of Methane float on top of that, and then there's hydrogen and helium above that.
    The Helium Layer is constantly being blasted away by solar winds as the planet's gravity isn't strong enough to hold it all in place. Estimates say the planet was originally 6-10 ME in size, but the gravitational forces were never enough to keep the mainly helium atmosphere in place, causing it to be blasted away over the billions of years. It will eventually reach a size where the planet's magnetic field will protect its atmosphere from the Solar Winds, but that's still almost a billion years away.

    (To do list...)
    (This is a large system that still has an asteroid belt and a bunch of moons. There's also the subject of the Regalti living in space, in a Dyson Swarm around Fevaultar, which I may kick to another article and keep this article only describing the natural bodies of the star system.)

    Cover image: by Chrispy_0


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    Grandmaster nnie
    Annie Stein
    25 Jun, 2021 08:29

    This is some impressive work! I really appreciate how organized the article is.

    Creator of Solaris & The Morning Realm -— On the Shoulders of Giants entry: Refugees of Mercury
    29 Jun, 2021 01:33

    Thanks. I'm glad you liked it!

    Current project: Kingdoms of Cassel
    25 Jun, 2021 21:53

    Wow this is a really good looking article! A well organised way to represent a start system with some nice drawings for each planet. The mining of Tula makes me think of a Kurzgesagt video where they suggested converting Mercury in a dyson swarm as well :p

    Feel free to check out my latest challenge article the Avaronian Empire if you want to see what I am up to!
    29 Jun, 2021 01:33

    Thanks for the kind words! I had the idea of a Dyson Swarm in progress floating in my head for a while after Isaac Arthur posted a video about Dyson Spheres. I decided to go with it a few years later when I watched the Kurzgesagt video about Dyson Spheres and they talked about mining Mercury to built it.

    Current project: Kingdoms of Cassel