Eclectic Universe

January 17, 2011

Hemera’s solar system formed when a molecular gas cloud called a nebula compacted into its center and formed a denser mass of dust. As material got attracted to the center of this cloud, it released heat through transforming gravity’s potential energy into the kinetic energy of motion. When gravitational forces began the collapse, the cloud’s slower rotation picked up under the conservation of angular momentum. As the center of this cloud started to attract more mass, the gravitational pull that this mass became stronger and the mass was able to pull into more mass and release more energy by this transformation. This process went on until the gravity of this gas ball became so massive that it started to crush the hydrogen in the center until it has dense enough and hot enough to form helium. Once this object was hot enough to undergo nuclear fusion of hydrogen into helium, it became a main sequence star.

As the solar system was forming, grains of rock and gas were swirling in an orbit around Hemera; these bits would collide frequently and sometimes these particles would smash into each other and form larger particulates. Eventually, these collisions would cause the orbits of all of the particles to roughly take on an average speed and direction, so the solar system would flatten out into a plane where all of the chunks of planetesimals would orbit around in. Eventually, those tiny grains of dust accreted into large rocky protoplanets, satellites ranging from the size of a continent to roughly the size of Mars. These planetesimals would collide with one another and form the planets we see now. Areios experienced one extraordinary collision that formed two of its three moons. A collision with a mercury-sized object called Dione created two silica-rich moons that orbit around the planet. The impact sent over 100 moonlet fragments into orbit around the planet and eventually formed three moons; one of them was cast out into deep space after six weeks. These two remaining moons, Otus and Ephialtes, are revolving farther and farther from the planet each year and this slows down the orbit of Areios over billions of years. Eventually, both of these moons will escape Areios’ gravitational pull and roll off into space. A third moon Eriboea was snagged in a later capture event that nestled it in between the first and third moons created by the impact event. Spiraling inward retrograde to the first and third moons, this moon will one day collide with Areios’ Roche limit and be ground up in a planetary ring. When that debris gets dislodged by gravity and some rains down on the planet, it would spell doom for anything unlucky enough to be alive at the time.

In Hemera’s solar system, we see a similar process of accretion that leads to two planets being formed; one is a massive gas planet that orbits far out into the Solar System; Alkyoneus, more massive than Jupiter, captured seven planetesimals into a lunar orbit before they could be smashed in a collision. These seven moons called the Alkynonides would large enough to be planets with satellites of their own, were they not captured by the gas giant’s formidable gravity. These planetesimals have plate tectonics, volcanism and a thin atmosphere, but orbit too far from the Sun to have liquid water on their surface. The radiation blasted from the gas giant irradiates anything on the surface, making it difficult for life to start. With no oceans or thick atmosphere to protect life from the harmful radiation, and it seems unlikely that life would spawn around Alkyoneus. The Alkyonides are in a part of deep space that’s far from the habitable zone where liquid water can exist on the surface of a planet. But liquid water could exist on these moons underneath the crust, warmed by the volcanism of the internal heat generated within the planet.

Our final stop is a tiny speck out in the far reaches of the solar system; this lonely planet is much like our Pluto, covered in a layer of ice along with its own little frozen satellite. Perses and the satellite Hekate were once part of the Alkyonides, but early on in the formation of the solar system, Perses and its satellite were dislodged from orbit and were lost in space until they finally reached a stable orbit at the very fringes of the solar system. Perses was the smallest of the Alkyonides, but still managed to snare a comet for a moon; when it was flung into a orbit at the outer regions of space, a comet settled in an orbit around Perses. Although Perses was once tectonically and volcanically active, it no longer produces a magnetic field or has any significant atmosphere. Now it just hangs out in the dead of space, the last stop in the solar system before the great beyond of the stars.

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