Enormous Universe

February 1, 2011

Alkyoneus would dominate the Areiosan night sky as one of the brightest objects visible to the naked eye. This is because Alkyoneus is a planet more massive than Jupiter and its girth carries a strong gravitational field causing perturbations or disruptions in the orbits of its neighboring worlds. This gas giant can act as a shield, diverting dangerous comets and asteroids away from Areios, or the massive planet’s gravity can act as a plow, pushing the rocky debris left from the solar system’s formation onto a collision course with the planet through planetary migration. Areios’ water, for instance, came in part from planetoids left over from the accretion stage of Areios’ formation. Rocky chunks of planet collided and the heat from friction melted those bits together, forming ever bigger planetesimals that lead to full-fledged planets. Alkyoneus was such a big planet that its gravity would keep hold of gases swirling around and it enveloped so much mass that the atmosphere keep building until it was a gas giant planet. Gas giants like Jupiter or Alkyoneus have a mostly-silicate core and layers of gas thousands of kilometers thick that girdle the planet. The composition of Alkyoneus and its atmosphere reflects how close it was to Hemera when it formed. The current theory for the formation of our solar system is explained in the nebular hypothesis; the solar system started out as a swirling ball of gas with a dim star still forming and sucking in mass at the center. As particle grains grew by colliding with each other in a process called accretion, the velocity and direction that these particles were whipping around in became more or less averaged out, so all of the material flattened out into a disk with everything basically moving about on the same plane, in the same direction, at roughly the same speed. A few collisions might redirect the path of individual moons or planets, but eventually most of the matter in the solar system would get incorporated into a planet. The exception to this in our solar system has to do with Jupiter’s gravity; its mighty pull tore apart anything orbiting around where a fifth terrestrial planet could be expected and kept it from forming anything bigger than the asteroid Ceres. In Areios’ solar system, there are a significant number of asteroids in a belt between Areios and Alkyoneus, representing a mass about equal to Earth’s moon.

The asteroids in Earth’s solar system are categorized by their composition. C-type asteroids are carbaceous (carbon-rich) and s-type asteroids are silicatious (silicate-rich), with more c-type asteroids farther from earth and s-type asteroids closer to us. Planets that form close to the star would have much less volatile content; volatiles are things like water or carbon dioxide that would boil away early on in the planet’s formation from the heat given off by its star. Hemera may be dimmer than our Sun, but anything caught too close to its radiation would melt. This is why terrestrial planets are found closer to the Sun in our solar system than the gas giants; as the solar system formed, the Sun wasn’t a fully-functional main sequence star and the composition of the nebula swirling around it was homogeneous. So as the Sun condensed and started to heat up, it melted the frozen ices closest to the Sun, leaving behind silicates and metals, which have a higher boiling point than ice. A star’s luminosity decreases with distance, so the radiation that reaches the middle to outer portions of the solar system wouldn’t melt the ices as much, so ices and volatile chemicals would make up a greater proportion of the planets farther out.

Once the planets formed, Alkyoneus’ gravity started to hold on to more gas vented from the crust or sucked in from the nebula surrounding the planet and the weight of the atmosphere crushed any hydrogen gas closer to the core into a metallic form. On the periodic table hydrogen is above lithium and the alkali metals, suggesting that because they’re in the same period, they would have similar properties. Hydrogen only behaves like a metal under the most extreme pressures, but when it’s condensed into a metallic form, the hydrogen nuclei form a tightly packed grid and the electrons are no longer confined to any individual proton, like in a sea of electrons. From the metallic hydrogen core, Alkyoneus’ atmosphere has bands of cold dense gases and other streams of hotter and faster moving gases. Alkyoneus’ atmosphere is made up of hydrogen, helium, and traces of methane, ammonia, cyanide, carbon monoxide and noble gases. There is more than enough organic material to start life, but there are concerns about buoyancy; any life has to stay in a layer of the atmosphere that’s not too hot or too cold, so altitude within the clouds has to be carefully maintained because if a creature rises too high or sinks too low, they could freeze, broil, or be torn apart by fierce winds. To maintain the right depth, a creature would need an organ like an air bladder (akin to the swim bladder on a fish that keeps it from sinking or floating to the top of the water), but primitive life couldn’t have a complex feature like this, so if a single-celled organism can’t have a swim bladder, it’s hard to imagine a complex creature ever being able to evolve.

Alkyoneus

A depiction of the gas giant Alkyoneus and its seven moons, the Alkyonides

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