Solakku

Currently unofficial lore, and in progress.

Solakku

Solakku, viewed through a filter
Characteristics
Evolutionary stage	Main Sequence
Spectral type	kA5hA8mF4
B−V color index	0.27
Details
Mass	1.92 M☉
Radius	2.174 R☉
Luminosity	15.87 L☉
Temperature	7803 K
Metallicity [Fe/H]	0.192 dex
Age	2.33 billion years
Orbit
Mean distance from Milky Way core	8200 light-years
Galactic period	45 million years
Velocity	340 km/s about Galactic Center

Solakku is the star at the centre of the avali home system. It is chemically peculiar and roughly classifiable as an A-type main-sequence star. It orbits the galactic enter at a distance of 8,200 light-years on average and is approximately 6.88 astronomical units (1.029×10⁹ km) away from Avalon. This corresponds to about 57 light-minutes.

Solakku forms a binary star system together with its red dwarf companion Crest. Alone, Solakku contains 92.85% of the total mass of this system and together with Crest, the two stars hold 99.81% of the total mass.

Like other main-sequence stars, Solakku produces energy through nuclear fusion of Hydrogen into Helium and emits most of this energy through light, in its case mostly visible light.

Composition

Solakku consists mainly of hydrogen and helium, though the composition is different between what is observable in the photosphere and what is present in the core. As it is already at least 77% through its total lifespan, Solakku’s core consists of 82% helium, with the remaining 18% being mostly hydrogen.

The measured photosphere composition is 78.3% hydrogen and 19.1% helium. Metals account for the remaining 2.6%, most notably 0.26% iron and traces of Calcium. This is an unusual high metallicity for an A-type star, making it an Am-type chemically peculiar star. This makes classification difficult. Visually, Solakku is an A8 star, but the calcium indicates A5 and the metallic lines F4, leading to its unusual spectral type kA5hA8mF4.

As elements heavier than hydrogen usually sink into the star over time due to gravity as the density of the core increases, it can generally be assumed that the metalicity of Solakku in its inner layers is even higher than what the photospheric composition would suggest. Internal metalicity explains the unusually low luminosity for a star of Solakku’s mass and age. The presence of metals increases the opacity of the star’s inner layers, that is by how much energy is inhibited from reaching the surface, which has a cooling effect on the outside, while increasing core temperature.

Structure

Structurally, Solakku consist of several zones, separated by short transition layers. The main layers are the core, convective zone, radiative zone and atmosphere, which is itself split into the photosphere, chromosphere and corona.

Core

The core of Solakku makes up about 20% of its radius and is the only place inside the star where nuclear fusion is possible due to the immense pressures and temperatures, which are estimated to be as high as 21 million kelvin.

Fusion takes place through both the proton-proton chain as well as the CNO cycle. Both of these processes convert hydrogen into helium at a combined rate of 9.849×10¹² kg/s, of which 6.759×10¹⁰ kg/s (0.7%) are converted into energy and 1.378×10⁸ kg/s (0.0014%) are released as neutrinos, the mass of which is equal to roughly 2% of Solakku’s total energy output.

Convective zone

Illustration of different stars’ internal structure based on mass. Solakku on the left has an inner convective zone and an outer radiative zone.

As the CNO cycle requires higher temperatures and produces more energy, it only occurs closer to the center of the core and produces more heat, while the proton-proton chain dominates the outer core, but produces less heat.

This, combined with the generally high energy output of the core, generates a temperature gradient which is of the right steepness to cause convection within the star, which extends up to 50% of Solakku’s radius. This process aids in heat transfer, moving energy away from the hot core and towards the upper layers of the star.

Radiative zone

Further away from the core, temperatures and pressures fall rapidly, forming steep gradients in both. The rapid change in density in particular is what ultimately makes convection impossible. The result is a layer which is in thermal equilibrium with relatively little plasma currents occurring inside.

This layer extends up to the surface of Solakku and transfers energy passively through thermal conduction or radiative diffusion, the latter of which gives this layer its name. Energy is only moved slowly through these processes, arriving at the final, observable surface temperature of Solakku. Along the way, it is inhibited by larger nuclei of various metals, slowing the transfer and leading to a cooler surface temperature.

Atmosphere

The atmosphere of Solakku consists of a photosphere, chromosphere and corona. The first of these is usually several hundred to a few thousand kilometres thick, a tiny fraction of Solakku’s full radius. The photosphere is defined as the visible surface of the star, or the deepest layer that is not opaque to visible light. Thermal photons produced here are able to escape to become starlight. The spectrum of this light can be approximated as that of a black-body radiating at 7803 K, the measured surface temperature of Solakku.

Particle densities drop off rapidly in the Chromosphere and Corona, though temperatures increase to over 20,000 K in the Chromosphere and millions of K in the Corona. It is possible to briefly observe the Corona once a day on Avalon, but only from the Valaya-facing side, when Solakku itself has just been eclipsed by the ice giant, with the Corona appearing as a faint white whisp trailing the star.

The radius of the Corona, and thus the Atmosphere as a whole, is variable from point to point, depending on speed and particle density of the stellar winds making up the Corona, but can be up to 24 times the radius of Solakku, past the orbit of Infernum. Infernum constantly casts a shadow in the stellar wind and disrupts its shape gravitationally and with its magnetic field, visible in the Corona as apparent smears, gaps and thin whisps.

Stellar radiation

Sunlight

Solakku mostly emits light of higher wavelengths due to its high temperature, leading to an apparent color of blue-tinged white. As well as providing visibility during daytime, this light is the primary energy source for life on Avalon, directly powering photosynthesis.

However, Solakku also radiates ultraviolet photons, which are attenuated by Avalon’s ozone layer. UV Radiation that reaches the surface can have positive biological effects, but higher wavelengths of it are dangerous and can be considered mutagens in some contexts. These emissions are therefore directly responsible for a number of biological adaptions seen particularly in lower latitudes on Avalon, where light has a more direct path through the ozone layer.

The light energy emitted by Solakku equals a total output power of 6.075×10²⁷ watts, but due to the inverse-square law, only about 456 W/⁠m² reaches Avalon. This value is known as the stellar flux and represents the amount of energy reaching Avalon’s position. The exact amount that reaches the surface may be lower and depends on atmospheric factors and latitude, but also on the exact positions of Valaya and Avalon in their respective orbits.

Stellar activity

Solakku generates a constant stream of charged particles at variable rates, known as stellar wind, which makes up the corona. This stellar wind, driven by radiative pressure, is not uniform, but varies in strength over latitude and longitude above Solakku. It consist primarily of electrons, protons and alpha particles which have been accelerated to up to 850 km/s, but also contains hydrogen atoms and atomic nuclei of various metals.

Otherwise, Solakku is particularly quiescent. As heat transfer is radiative in its outer zone, there are no convection cells to shift the plasma making up Solakku’s surface. On lower-mass stars, convection causes plasma currents and powerful magnetic fields, powering extreme events such as stellar flares, but this does not occur on Solakku.

Instead, interactions between Infernum and Solakku have a profound effect. Due to Infernum’s low orbit and high mass, its gravity will pull at the plasma below it, creating a tidal wave trailing Infernum. As this wave moves faster than the rotation period of Solakku, it crashes into the slower-moving plasma and drags it along, leaving behind a trail of vortices and other shock-induced currents. These plasma currents in turn create magnetic fields, which may combine to create further observable effects, such as plasma loops, which occur when plasma is confined within one of these fields and lifted above Solakku’s surface.

These rogue fields inevitably reconnect with each other, or the magnetic field of Solakku as a whole, releasing bursts of energy in the form of radiation all across the electromagnetic spectrum, up to ultraviolet light and X-Rays. These stellar flares occur regularly on Solakku’s surface, directly below Infernum’s orbit. However, they are relatively weak compared to ones on lower-mass stars, where they are driven by much stronger convection currents. Rarely, a multitude of these events occur in close proximity and combine, releasing a single, more powerful flare.

Effects

Stellar wind is almost entirely warded off by the combined magnetospheres of Avalon and Valaya, though these same fields may concentrate the charged particles received from the stellar wind into Van Allen belts, which block spacecraft from parking inside whole ranges of orbits. Other celestial bodies with magnetospheres also exhibit these effects. On bodies without a magnetic field, the stellar winds may reach the surface and chemically transform it, such as with the formation of Tholins.

Avalon’s atmosphere, especially the ozone layer, is responsible for attenuating or even completely filtering the dangerous ultraviolet and X-Ray radiation of stellar flares. Additionally, Infernum’s orbit is at a high inclination, misaligning most flares with the positions of the other planets, except for two brief time periods in each planet’s orbit, where it passes through Infernum’s orbital plane. The majority of energy released by these flares is thus only rarely aimed directly at any celestial body. Only Magnus and Solvis are the most at risk, due to their proximity to Solakku and relatively frequent passes through the aforementioned plane.

Both types of emissions have a profound impact on space travel, however. Spacecraft situated close to Avalon, Valaya or any celestial body with or within a magnetosphere are still protected from stellar winds, but interplanetary space possesses a dangerously high background radiation count caused by stellar wind. Both computer systems and crewed modules aboard spacecraft traversing this space must thus be built to mitigate or block the effects of stellar wind emissions.

The more powerful stellar flares pose an acute danger within a specific area, aligned with Infernum’s orbital plane and close to the star. If one strikes a spacecraft, it may cause electrical malfunctions on space probes and severe radiation exposure to lifeforms on crewed vessels. The energies of stellar flares are not inhibited by Solvis’ magnetosphere and can thus reach any spacecraft outside of its atmosphere.

However, the possible damage that may be caused in these scenarios is significantly less than flares in lower mass stars, such as Crest. Most modern crewed spacecraft are constructed to handle other stars’ stellar activity as well, meaning they can easily protect against Solakku’s flares. Historically, however, stellar wind and stellar flares lead to major difficulties in non-FTL deep-space exploration.

Life phases

Formation

Solakku formed approximately 2.6 billion years ago through gravitational collapse of a molecular cloud, beginning its life cycle. This occurred most likely at the same time as Crest’s formation, as they are projected to have very similar ages. However, Crest does not share all of Solakku’s chemical peculiarities, so the two stars may have formed in different regions of their molecular cloud. Another theory posits that Crest was captured by Solakku and the overlapping ages are merely a coincidence, but this is rather unlikely. The difference in composition is more easily explained by the high difference in mass between the two stars.

Some meteorites orbiting Solakku and captured for study were found to contain traces of decay products of short-lived nuclei which only form in the extreme conditions of supernovae. The amount indicates that a number of these took place near this molecular cloud, the shockwaves of which would’ve triggered the formation of Solakku and enriched the environment with additional metals, potentially explaining Solakku’s chemical peculiarity.

As Solakku was forming, a disk of gas and cloud, known as a protoplanetary disk would’ve also accumulated around it. The particles making it up then slowly accreted into larger chunks over millions of years, which could repeatedly collide and combine to form planets.

Closer in to Solakku, this process would’ve stopped at creating silicate and metal rich terrestrial bodies, such as Magnus and Solvis, but beyond the frost line, temperatures would’ve been cold enough for volatile molecules to freeze into solids and further accumulate on any forming planets, pushing them past the mass required to collect thick envelopes of lighter gases, primarily hydrogen, forming the giant planets Valaya, Edith and, to a much lesser extent, Frost.

The planets then slowly migrated from their initial positions over time due to gravitational interactions, most prominently Infernum, which was transferred from its position beyond the frost line to a close orbit around Solakku. After just a few million years, increasing stellar winds from Solakku would’ve blown all remaining dust and gas away, completing the process.

Main Sequence

Position of Solakku within the Hertzsprung-Russell Diagram, showing it is currently a main-sequence star.

Solakku is just over three quarters through its main-sequence stage, during which hydrogen in its core fuses into helium. Approximately 3.1 billion years will have passed between its formation and transition into the red giant phase. The higher metalicity of Solakku has served to draw out this lifespan, which is longer than its mass might suggest. As the higher opacity caused by the metals reduces the amount of energy which can reach the surface, this also puts a cap on how fast hydrogen can fuse in the core, reducing burn rates and extending the lifespan.

During its main-sequence phase, Solakku has gradually become cooler in its core and surface, but larger in radius, with the overall effect being a increase in luminosity, which is now sitting at just over 45% what it was initially. This luminosity increase has been gradual up to this point, but is approaching a point of accelerating. Current models predict that the increase in energy output will render Avalon uninhabitable in 100 to 200 million years and is already responsible for the slow shrinking of Solvis’ oceans, which are set to evaporate completely in anywhere from 10 to 50 million years.

After hydrogen exhaustion

Solakku is not massive enough to undergo supernova. Instead, core hydrogen fusion will cease in 770 million years, with the core contracting rapidly without the energy released by fusion to push against gravity. This contraction will lower a substantial amount of mass down the gravity well, releasing a massive amount of potential energy. This energy is transferred into the outer layers of the star, causing it to increase dramatically in radius and luminosity after a brief decrease in brightness, up to 25 R_☉ and 220 L_☉. At the same time, its temperature falls due to the increase in surface area, to as low as 4800 K, making it appear visually pale orange. Solakku has entered its red giant phase.

During this time, hydrogen fusion re-ignites in a shell around the dead core, however, this shell is thin. As the star’s core was convective during its main-sequence, the unfused hydrogen and the fusion products were mixed evenly, leading to hydrogen depletion everywhere in the core almost simultaneously.

Due to Solakku’s high mass and metalicity, it takes only a few million years for enough heat to build up to ignite helium fusion in a helium flash, from which point onwards it will fuse helium to carbon and oxygen using the triple-alpha process. Initially, Solakku now contracts again as it is no longer being inflated by the release of potential energy and cools further, reaching thermal equilibrium again. Its temperature will reach as low as 4100 K while its radius falls below 160 R_☉.

This helium-burning phase will last at least 300 million years, during which carbon and oxygen steadily accumulate in the center of the store, forming a growing dead core. It is also likely that the convection zones will extend all the way to the surface during this time, deforming the shape of Solakku and powering intense stellar activity, such as massive flares. Towards the end of this phase, as even helium burning is increasingly restricted to a shell around an inert core, Solakku will repeat its earlier inflation, but at an even greater scale. This is known as the asymptotic giant phase, during which the star’s radius will rise to over 0.75 AU, with an accompanying increase in luminosity to over 4000 L_☉.

All these steps in Solakku’s evolution past the main-sequence, especially the asymptotic giant phase, will cause massive damage to what is left of Solakku’s planetary system at this point, due to intense luminosity heating most of the celestial bodies past the melting points of most metals. Solvis, Avalon, Nevu and perhaps Valaya will be stripped of their atmospheres and all liquids that are not molten rock, if this has not occurred already. Magnus will be completely lost sometime during the asymptotic giant phase, when Solakku’s radius grows past the planet’s orbit. However, Tusoya may briefly become habitable starting at the red giant phase, with volatiles on its surface melting and a thick atmosphere forming.

After less than 10 million years of the asymptotic giant phase, Solakku will enter the final active phase of its life. Almost all the helium left over from the main-sequence has been turned into other elements and helium fusion can now longer take place consistently. Instead, the remaining hydrogen fusing in a shell around the core repeatedly has to build up helium until a threshold is reached where all the buildup fuses explosively all at once, generating intense pulses of energy.

During the following 1 to 2 million years, these pulses rip away material from the outer layers of the star, shedding it into a planetary nebula. Solakku is expected to loose at least 60% of its mass through this process, dropping in luminosity and core temperature the whole time, until, finally, neither helium nor hydrogen fusion can be sustained inside any longer. With nothing holding it back, Solakku will fully collapse into a carbon-oxygen white dwarf, heating up to over 100,000 K in the process, but compressed into a space just larger then the radius of Solvis. This inert object with an incredibly low luminosity will now spend the next trillions of years slowly cooling.

Location

Stars and star systems within 5 light-years of Solakku.

Solakku is situated relatively close to the galactic core, orbiting the center point of the galaxy at a distance of just around 8,200 light-years. This means it is situated in a dense stellar neighborhood, with around 20 stars less than 5 light-years distant from it, most of which are less massive, dimmer objects. The closest star not gravitationally bound to Solakku is Karat, at under one light year distant.

Due to this, Solakku encounters flybys of other stars at a somewhat frequent rate, roughly every 15,000 years another star passes within 0.5 light-years of Solakku. Even closer approaches have lower probabilities of occurring, but could disrupt the orbits of Solakku’s planets and Crest. It is likely that this happened at least once in the past, shifting several planets inwards to their current orbits.

However, Solakku’s age is also relatively low for a star, which statistically lowers the amount of such encounters that could probably have happened so far. Currently, only Karat is slated for a relatively close flyby of Solakku in the near future, estimated to pass within 0.6 light-years in 5,000 years.

The following table lists all known stars within a radius of 5 light-years around Solakku. An interactive map is accessible at this link. Only the primary element of each system is shown.

Designation	Distance (ly)	Stellar class
Solakku	0	kA5hA8mF4
Karat	0.96	DA4.4
Wanderer	1.02	F2V
Ak-Vi	1.43	K6V
Arkut	1.89	A2V
ISC-233	2.41	T1.5
Thoje	2.51	G0V
Tsija’s Star	2.93	M7V
Rivalu	3.16	K6V
ISC-57	3.27	L4
57 Sharu	3.34	M9V
Tarik 27-C	3.38	K7V
ISC-22	3.43	M5V
ISC-87	3.87	L2.5
ISC-89	4.05	T6.5
ISC-168	4.20	K7V
Tarik 23	4.23	M7V
Evits 3	4.24	G2V
Evits 9	4.37	M2V
Amber Light	4.37	M1 III
Atsavara	4.45	F4V
Tarik 59	4.57	DZ11.8
Arakvus	4.95	A0V

Star system

Solakku has seven known planets orbiting it, as well as one other star. This includes five terrestrial planets, two gas giants and one ice giant. There are also numerous bodies generally considered as dwarf planets, an asteroid belt, numerous comets, such as Crravk, and the companion star Crest. Six of these bodies also have natural satellites of their own.

Solakku’s planetary system in particular is roughly separated into two parts, the inner system before the frost line, up to and including Valaya, and the outer system, starting at Edith. The outer system lies past the frost line, where it is cold enough for volatile chemicals to freeze, covering certain celestial bodies in those ices. The asteroid belt is also in this region, in-between Frost and Tusoya, consisting of asteroids made up of silicates and frozen volatiles. This is material left over from the formation of the system that was not used in the formation of any celestial body. The most massive object orbiting within the belt is the dwarf planet Haväa.

Due to the gravitational influence of Crest, there is a limit on how far away a celestial body, such as an asteroid or comet, can orbit from Solakku before inevitably being disrupted by Crest. There is evidence of a thin shell of asteroids surrounding the Solakku-Crest binary as a whole at a distance of at least 600 AU labeled as the Kreivali Sphere. Beyond that, the regular influence of interstellar objects prevents any stable orbits around Solakku.

As Solakku has a higher than average mass and the radii of planetary system orbits usually scale with star mass, distances between Solakku’s planets are vast. Generally, the farther a planet is from Solakku, the larger the distance between its orbit and the orbit of the next nearest object. For example, the distance between Valaya and Edith is around 5 AU, but the distance from Edith to Frost is over 14 AU.
If Solakku was a ball with a diameter of 10 centimetres (3.9 in), Valaya would be a sphere of 0.4 centimetres (0.16 in) positioned at a distance of 620 metres (2,030 ft) away.

The below table lists all planets of Solakku and their largest or most significant natural satellites. Crest’s orbit is also listed for scale.

Name		Mean distance from Solakku	Equatorial Radius	Mass	Orbital Period (Around Solakku) in years	Avg. air temperature (if applicable)
Infernum		0.025 AU	1.67 RJ	3.1 MJ	0.0028	2,910 °C (5,270 °F)
Magnus		0.56 AU	0.494 R🜨	0.075 ME	0.3
Solvis		2.91 AU	0.825 R🜨	0.525 ME	3.5	27.85 °C (82.13 °F)
	Mol		0.1 R🜨	2.327×1021 kg
Valaya		6.88 AU	0.878 RJ	0.686 MJ	13	65.85 °C (150.53 °F)
	Mov		0.14 R🜨	1.606×1022 kg
	Rivala		0.15 R🜨	2.087×1022 kg 0.03 ME
	Ralu		0.35 R🜨	2.804×1023 kg 0.04 ME
	Avalon		0.711 R🜨	0.126 ME		−63.15 °C (−81.67 °F)
	Nevu		0.41 R🜨	0.07 ME		−83.15 °C (−117.67 °F)
	Char		~21.4 km	4.539×1016 kg
Edith		12.58 AU	0.724 RJ	0.18 MJ	32.1	−46.15 °C (−51.07 °F)
	Crinta		~138 km	6.058×1019 kg
	Ghoruh		0.4 R🜨	0.1 ME
	Trultiva		0.13 R🜨	4.696×1021 kg
	Trultosa		0.1 R🜨	6.281×1021 kg
	Kaao		~20 km	7.6×1019 kg
Frost		27.43 AU	1.96 R🜨	4.88 ME	103.6	−164.15 °C (−263.47 °F)
	Res		0.3 R🜨	1.644×1023 kg 0.02 ME
	Thahali		0.27 R🜨	5.423×1022 kg
	Kalltsu		~15 km	2.429×1017 kg
Haväa* *dwarf planet / asteroid belt		56 AU	0.16 R🜨	2.12×1022 kg 0.003 ME	302.7
Tusoya		73.4 AU	0.97 R🜨	0.57 ME	453.7	−214.15 °C (−353.47 °F)
	Arkuvos		0.13 R🜨	8.281×1021 kg
Crest		322 AU	0.17 R☉	0.143 M☉	4022.4