A write-up of the star Galen Alpha, part of the setting for Tyranny of the Daleks. This is for the Doctor Who Roleplaying Game from Cubicle 7.
Designation: Galen Alpha
Spectral Type: G1V main-sequence star
Mass: 1.04 × Sol
Radius: 1.07 × Sol
Luminosity: 1.18 × Sol
Surface Temperature: 5820 K
Age: 3.07 billion years
Rotation Period: 24.0 days
Distance from Galen Beta: 0.542 light-years
Surface Gravity: 0.249 km/s²
Core Temperature: 15.3 million K
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| Galen Alpha, with Galen Beta visible about half a light year distant. Also shown are the orbits of some of Galen Alpha's planets |
Overview
Galen Alpha is a sun of quiet majesty, a G1V main-sequence star burning with a steady gold-white radiance similar to Earth’s own Sun. At 1.04 solar masses and 1.18 times its luminosity, it is just slightly more powerful and somewhat younger than Sol, a warm and vigorous stellar engine nearing the midpoint of its life. Yet, unlike humanity’s familiar star, Galen Alpha shines across an interstellar void almost devoid of neighbours, in one of the Galaxy’s most remote and tranquil regions.
Orbiting serenely in this isolation, Galen Alpha and its distant companion, the faint red dwarf Galen Beta, form a binary system whose gravitational bond stretches across half a light-year, making it one of the widest stable stellar pairings known to the Galactic Federation. Their lonely partnership defines the Galen System, a rare island of light in a sea of cosmic darkness.
Origins of the Galen System
The Galen System lies within the Thayrn Assemblage, a small and isolated group of only nine stars scattered across a fifty light year radius at or rather beyond the remote end of the Carina–Sagittarius arm, on the far side of the galaxy from Earth's Solar System. Beyond this pocket of stars, space becomes extraordinarily empty: the nearest other systems lie at least sixty light years farther out towards the last reaches of the spiral arm, and even these are themselves lonely outposts on the thinning edge of the galactic disk. The interstellar medium in this region is exceptionally sparse, making the existence of any star cluster here a surprising anomaly.
After the Milky Way settled into its mature form billions of years ago, the galactic frontier where the Thayrn Assemblage now resides contained only a thin, diffuse cloud of hydrogen. The material was so insubstantial that no substantial molecular clouds formed, and therefore no stars. For around a billion years, this region remained dark and entirely empty.
Around eleven billion years ago, a large galaxy known as “Kraken” was drawn into the Milky Way and disrupted in a collision between the two galaxies. Tidal forces from the crash scattered streams of stars and dust throughout the outer halo, including into this far-flung sector. For the first time, heavier elements, including some exotic molecular forms uncommon in the inner Galaxy, drifted into the region. Though this enrichment raised the metallicity slightly, the density was still far too low for star formation.
The decisive moment came much later. Roughly 3.5 billion years ago, the shock front of a distant gamma-ray burst swept through the remote outskirts of the Carina–Sagittarius arm. Though the GRB itself had occurred many thousands of light years away, far enough not to sterilise worlds, its pressure wave pushed additional enriched material into this frontier, compressing the interstellar medium into higher-density pockets.
One such pocket collapsed into a molecular cloud around a hundred light years across. Compared to the great star-forming complexes near the galactic centre, this cloud was thin and inefficient, but it was dense enough to ignite a brief and localised episode of star birth.
This triggered collapse formed a small handful of protostars in a compact region at the cloud’s centre. Because they formed together and possessed nearly identical initial velocities, they have remained loosely associated ever since, a fragile cluster adrift at the galaxy’s edge. These stars became the Thayrn Assemblage.
Among them were Galen Alpha and its low-mass companion Galen Beta.
Some of these protostars retained protoplanetary discs; Galen Alpha’s disc was unusually massive for such a remote environment. From it formed a rich and diverse planetary system, including the garden world Galentor (Galen Alpha II).
Stellar Character and Behaviour
Spectroscopically classified as G1V, Galen Alpha’s light falls midway between the warm yellow of Sol and the paler hue of an F-type star. Its photosphere burns at 5820 Kelvin, giving the star a faintly whiter cast than the Sun when viewed directly through a filtered optical array. The stellar surface seethes with granulation and slow convection, driving a cycle of magnetism and solar weather that is relatively gentle compared to younger or more active stars.
Federation spectroheliographs have revealed a periodicity in its starspot cycles of approximately 8.9 years, shorter and less intense than Sol’s eleven-year rhythm. This subdued magnetic activity, combined with the system’s extreme isolation, contributes to the remarkable climatic stability of Galen Alpha II (Galentor), the system’s fertile, life-bearing world.
At its core, Galen Alpha sustains hydrogen fusion at 15.3 million Kelvin, producing a luminosity 18% greater than Sol’s. This mild excess of energy places Galentor in a slightly wider orbital band than Earth but still within the comfortable limits of a temperate biosphere.
A Star Alone
Astronomers from the Federation Stellar Bureau have remarked that Galen Alpha’s environment is among the most sparsely populated in known space. The nearest stellar system lies nearly 27 light-years distant, and beyond that, the local stellar density falls sharply. No interstellar clouds, molecular nebulae, or supernova remnants disturb the surrounding void.
This extraordinary quiet has made Galen Alpha a prime example of a “cosmic refuge”, a star and its worlds evolving in near-perfect isolation for billions of years. Its isolation has shielded its planetary system from the supernova shocks, radiation bursts, and gravitational disturbances that shape the evolution of more crowded regions closer to the Galactic Core.
As one Federation scientist remarked:
“Galen Alpha is a clock that has never been reset, a pure record of stellar evolution in slow motion, undisturbed by the noise of the Galaxy.”
The Binary Bond
The companion star, Galen Beta, lies at the extraordinary distance of around half a light year, a separation of around 34,000 astronomical units. A dim red dwarf, one of the smallest found in the Galactic Federation, it circles its larger sibling in an orbital period measured not in centuries but in millennia. Despite this, the two remain gravitationally bound, their motions locked in an elegant celestial dance that has endured since the system’s birth.
Astronomers speculate that Galen Alpha and Beta formed together from the same protostellar cloud, but that an early interaction with a passing interstellar body flung Beta into its current distant orbit. Its gravitational influence has profoundly shaped the system’s structure, sweeping clean the outer debris and sculpting the cometary reservoirs into fragile shells. Their enormous distance as a binary star means that the presence of Galen Beta makes no discernible difference to Galen Alpha’s planetary system of ten principal planets, numerous moons, comets and asteroids.
Scientific Significance
Galen Alpha’s moderate metallicity, albeit rather lower than that of Sol, offers insights into star formation at the extreme rim of the Milky Way. Its composition indicates that the heavy elements required for planet formation were still relatively abundant in this region three and a half billion years ago, implying earlier episodes of stellar generation farther inward in the Galaxy had already seeded this frontier with the materials of life.
For astrophysicists, the Galen system is thus a paradox: a cradle of planetary richness located in one of the most barren sectors of the Galaxy. How such a system formed and survived so far from the spiral arms remains one of the great puzzles of deep-space astronomy.
A Beacon at the Edge
Seen from afar, Galen Alpha burns like a solitary lantern suspended over a dark ocean, a symbol of endurance and constancy at the farthest limits of the Milky Way. To the explorers and settlers who have crossed the void to reach it, it represents both refuge and reminder: that even at the edge of the known, light persists.
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