Caelus

Caelus (Eris) is the most massive and second largest dwarf planet in the Sol system. It is 2,326 kilometers (1,445.3 mi) in diameter and is 27% more massive than Saturn, although Saturn is larger in radius and volume. Caelus has 0.27% the mass of Terra. This dwarf planet only has one, small moon, and is outside of the Titan Belt, flung out and detached from the early Sol system by Neptune. Its farthest distance from Sol is 97.6 AU, three times that of Saturn. Caelus is named after the Roman titan who is the god of the sky, and father of the titans.

## Composition

### Surface

The surface of Caelus is similiar to that of Saturn, having methane ice on its surface. Due to the eccentric orbit of Caelus, its surface temperature varies between 30 and 56 K (−243.2 and −217.2 °C). Unlike reddish-brown Saturn and Triton, Caelus is ice-white. This is due to the methane deposits condensing onto its surface, covering up any red deposits of tholin.

### Structure

Caelus is around the same size as Saturn. It also has an albedo of 0.96, higher than that of any other large body in the Sol System except Rumina, a moon of Saturn. The high albedo is due to the surface ices being replenished because of temperature fluctuations as Caelus's eccentric orbit takes it closer and farther from Sol. Caelus is 27 percent more massive than Pluto. Caelus has a density of 2.52g/cm^3, substantially denser than Saturn, and thus must be composed largely of rocky materials.

## Orbit and rotation

Caelus has an orbital period of 558 years. Its maximum possible distance from the Sol is 97.65 AU, and its closest is 37.91 AU. Caelus's orbit is highly eccentric, and brings Caelus to within 37.9 AU of the Sun. This is within the orbit of Saturn, but still safe from direct interaction with Neptune (29.8–30.4 AU). Caelus is actually in a 17:5 resonance with Neptune. Unlike the eight planets, whose orbits all lie roughly in the same plane, Caelus's orbit is highly inclined relative to the equator of Sol: It is tilted at an angle of about 51 degrees to the equator of Sol.

## Moons

### Dies

Dies is the only moon of the dwarf planet Caelus. It is named after the Roman titaness of day and the mother of Caelus. Its diameter is about 420 km in diameter and is much, much redder than Caelus. Its orbital period is 15.774 Terra days. It is similiar to the moons of Saturn in terms of economic importance. However, due to the extreme distance of the Caelian system from Terra, it is even less populated and has less economic importance overall. Dies has a sustainable population of 70,912 people.

## Civilization

### Initial settlement

Since Caelus is even further from Terra than Saturn, and also not having any extremely valuable resources, Caelus makes for a less desirable target for potential colonists. Like many bodies of similiar composition, Caelus had to be colonized in a similiar way. Rotating gravity had to be provided and crucial chemicals for human life were mined from the crust to sustain the early colony. Using solar power this far out is insane and either fission or fusion nuclear power is used for energy instead.

### Economy and human geography

There are no extremely valuable resources on Caelus, with the exception of essential nitrogen and water in spaceflight. In addition to the far distance from Terra, Caelus does not have very high economic valuable. However, it serves as the second most important hub of the outer Sol system due to its relatively high population for an object so far from Terra and having no notable resources. Caelus has a sustainable population of about 20.4 million people.