Hemithea is a binary red dwarf system situated in Orithyia and is home to Orithyian Triple Alliance.
Stars
The two stars orbit each others in 105.532 earth years. The primary is of M0 V spectrum with a mass of 0.534 M☉ and a radius of 0.66063 R☉ at 6.91 au. The secundary is of M2.5 V spectrum with a mass of 0.32251 M☉ and a radius of 0.36072 R☉ at 11.43 au.
Homeworlds
Belletana
Belletana, the fourth planet of the star Hemithea A, is a warm D-class world and the homeworld of the Belletanians. With a surface gravity of just 0.42279 g and a radius of 2,901.1 km, it is a small, low-mass planet at only 0.08747 Earth masses. Belletana is tidally locked and orbits at a semi-major axis of 0.14 AU, completing a revolution every 25.992 Earth days. It has a slight orbital eccentricity of 0.027 and a minimal axial tilt of 3°53′28.08″, contributing to the world’s lack of seasonal variation. The climate on Belletana is consistently warm, with an average surface temperature of 70.1 °C. Its dense atmosphere measures 4.93 atm and is composed primarily of carbon dioxide (99.7%) with a small fraction of oxygen (0.258%). Belletana supports organic, terrestrial multicellular life and is currently populated by approximately 1.7 billion Belletanians. The planet is governed by the Orithyian Triple Alliance, and it serves as the location of the alliance’s senate. One natural moon orbits the planet.
Thurgock
Thurgock, the fifth planet of Hemithea A, is a temperate E-class world and the native home of the Thurgock species. Like its neighbor Belletana, Thurgock is tidally locked and experiences no seasonal variation due to its zero-degree axial tilt. However, its environment is vastly different — frigid and dry, with an average surface temperature of -22.7 °C. Thurgock has a mass of 0.42219 Earth masses and a radius of 5,870.42 km, resulting in a surface gravity of 0.49837 g. It orbits at 0.27 AU and completes a year in 72.018 Earth days, with a nearly circular orbit marked by an eccentricity of 0.015. The planet has a very thin atmosphere at 0.127 atm, primarily consisting of carbon dioxide (84.6%) and oxygen (14.6%). Despite the cold, Thurgock supports both terrestrial and marine organic multicellular life. Its current population is about 1.85 billion Thurgock. The planet is under the control of the Orithyian Triple Alliance and hosts the executive branch of the alliance government. Thurgock has three moons.
Pavone
Pavone, the sixth planet of Hemithea A, is a cold D-class world and the ancestral home of the Pavonirs. Unlike the tidally locked Belletana and Thurgock, Pavone rotates once every 22 hours, 59 minutes, and 2.29 seconds. It is considerably more massive, at 2.0083 Earth masses, with a radius of 9,998.42 km and a resulting surface gravity of 0.81731 g. The planet orbits at 0.49 AU with a period of 170.402 Earth days and an orbital eccentricity of 0.03. Its axial tilt is a sharp 48°27′50.83″, resulting in both mild and extreme seasonal shifts depending on the region. The climate is intensely cold, with an average temperature of -86.0 °C. Its thin atmosphere measures 0.339 atm and is composed of 99.8% carbon dioxide and 0.156% oxygen. Pavone supports organic terrestrial multicellular life and is inhabited by around 2.23 billion Pavonirs. Like its sister planets, Pavone is administered by the Orithyian Triple Alliance and has a notable satellite system consisting of six natural moons.