Halcyon

The ocean planet Halcyon is a vibrant hub of Neptunian culture. It is a heavily-terraformed planet whose transhuman inhabitants live in a variety of island cities, deep-ocean homesteads, and floating tribes. It has been continuously inhabited for over 8000 years, though its current population is difficult to describe exactly, thanks to the ubiquity of gestalt minds, swarm bodies, and other nonstandard approaches to individuality.

Physical Characteristics

• Primary: Aeolus (G0, 1.22 MS)
• Average Orbital Radius (pre-colonization): 198.6 × 10⁶ km (1.32 AU)
• Average Orbital Radius (current): 159.5 × 10⁶ km (1.066 AU)
• Orbital Period (pre-colonization): 503.92 d
• Orbital Period (current): 364 d (exactly)
• Rotational Period (pre-colonization): 204.3 h
• Rotational Period (current): 24 h (exactly)
• Mass: 0.92 M_E
• Radius: 1.13 r_E
• Surface Gravity: 0.72 g
• Ocean coverage: 99.97%
• Land surface area: ~200,000² km (~12× the surface area of the Hawaiian Islands)
• Axial Tilt: 31 degrees

Halcyon is the fourth of five planets from its primary, Aeolus. The Aeolus system is unusual for being rich in extraplanetary mass. The only high-mass planet in the system is the fifth planet, Enarete. All the mass beyond Enarete is tied up in icy asteroids and minor planets, essentially a Kuiper-belt-like structure that spans the equivalent of the orbits of Jupiter through Uranus.

Enarete has a mass of 3.5 Jupiters, and has essentially cleared the inner system of rogue asteroids and comets, but the inner planets (Calyce, Pisidice, Perimede, and Halcyon itself) show evidence of significant impacts, indicative of a Heavy Bombardment Period lasting almost 2 Ga, several times longer than Earth’s own. The combination of the ice-rich nature of the system and the prolonged period of bombardment resulted in Halcyon having a significant axial tilt for a planet without a natural satellite and a very high water content. Despite that high water content and a relatively biocompatible surface temperature, Halcyon seems to have never developed indigenous life, possibly because the lack of tides and land surface prevented the complex mix of factors required for biopoiesis.

History

Halcyon was selected for colonization 14 <acronym title="kiloyears">ka</acronym> ago by the nascent Neptunian culture which was in search of a homeworld. It fit all their criteria perfectly, an Earthlike planet with a very high ocean surface area but no native life to make accommodations for. The factors that were least Earthlike, namely the orbital and rotational periods and associated surface temperature conditions, were easily rectified via gravitic engineering.

The process of changing the orbit and rotation of the planet took several ka, and were accomplished using a smartmatter gravitic array. The array encircled the planet, increasing its orbital and rotational speeds while keeping the orbit stable. As this slow process progressed, life-seeding began, starting with simple archaea and bacteria that would not be significantly affected by the changing day and year cycles.

The day and year were eventually stabilized to an idealized Earth norm, exactly 24 standard hours per day, and exactly 364 standard days per year, to most-effectively implement the Neptunian Calendar. At that point, the smartmatter array was reconfigured into an artificial satellite, with its gravitic beam tuned to produce tides on the planet below. The artificial moon was named Ceyx and set up with a five-day revolution around Halcyon, again to fit with previously-established Neptunian calendar principles.

Ceyx

Ceyx is one of the most striking features of the Halcyonian sky. With its faster revolution, it is much closer to Halcyon than Luna is to Earth, but its distributed nature allows its apparent size to be tuned precisely. It appears as a fuzzy disc about three times the size of Luna from Earth, and is several times brighter, thanks not only to its proximity, but to the higher albedo of its components. The smartmatter components are actually powered by Aeolus’ light, but the frequencies they absorb shift smoothly over its five-day cycle, to properly balance and buffer the energy input. The result of this is that the ‘phases’ of Ceyx are displayed via a cycle through the visible spectrum, rather than by a change of observed shape.