View source for Solakku

{{unofficial}}

{{Starbox begin
| name = Solakku
}}
{{Starbox image
| image = [[File:Solakku from space.png|250px]]
| caption = Solakku, viewed through a solar filter
}}
{{Starbox character
| type = [https://en.wikipedia.org/wiki/Main_sequence Main Sequence]
| class = kA5hA8mF4
| b-v = 0.27
}}
{{Starbox detail
| age = 2.33 billion
| mass = 1.92
| radius = 2.174
| luminosity = 15.87
| temperature = 7803
| metal_fe = 0.192
}}
{{Starbox orbit
| gperiod = 45 million
| gvelocity = 340
| mkdist = 8200
}}
{{end}}

Solakku is the star at the centre of the avali home system. It is chemically peculiar and roughly classifiable as an A-type [https://en.wikipedia.org/wiki/Main_sequence main-sequence] star. It orbits the galactic enter at a distance of 8200&nbsp;[https://en.wikipedia.org/wiki/Light-year light-years] on average and is approximately {{convert|6.88|au|km}} away from [[Avalon]]. This corresponds to about 57&nbsp;[https://en.wikipedia.org/wiki/Light-minute light-minutes].

Solakku forms a binary solar system together with its [https://en.wikipedia.org/wiki/Red_dwarf 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 [https://en.wikipedia.org/wiki/Nuclear_fusion nuclear fusion] of Hydrogen into Helium and emits most of this energy through light, in its case mostly visible light and infrared.

= 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 [https://en.wikipedia.org/wiki/Chemically_peculiar_star 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&nbsp;million kelvin.

Fusion takes place through both the [https://en.wikipedia.org/wiki/Proton%E2%80%93proton_chain proton-proton chain] as well as the [https://en.wikipedia.org/wiki/CNO_cycle CNO cycle]. Both of these processes convert hydrogen into helium at a combined rate of {{Val|9.849|e=12|u=kg/s}}, of which {{Val|6.759|e=10|u=kg/s}} (0.7%) are converted into energy and {{Val|1.378|e=8|u=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 ==

[[File:Heat Transfer in Stars.svg|thumb|300px|Illustration of different stars’ internal structure based on mass. Solakku on the left has an inner convective zone and an outer radiative zone.|alt=See caption]]

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 steep enough to cause [https://en.wikipedia.org/wiki/Convection 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.

{{clear}}

== 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.

This layer extends up to the surface of Solakku and transfers energy passively through [https://en.wikipedia.org/wiki/Thermal_conduction thermal conduction] or [https://en.wikipedia.org/wiki/Radiation 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.

== Atmosphere ==

The atmosphere of Solakku consists of a photosphere, chromosphere and corona. The photosphere is defined as the visible surface of the star, or the deepest layer that is no opaque to visible light. Thermal photons produced here are able to escape to become sunlight. This zone is usually several hundred to a few thousand kilometres thick, a tiny fraction of Solakku’s full radius.

The spectrum of the light emitted here can be approximated as that of a [https://en.wikipedia.org/wiki/Black-body black-body] radiating at 7803&nbsp;K, the measured surface temperature of Solakku.

Particle densities drop of rapidly in the Chromosphere and Corona, though temperatures increase to over 20,000&nbsp;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 solar winds making up the Corona, but can be up to 24 times the radius of Solakku, past the orbit of [[Infernum]].

= Solar 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 [https://en.wikipedia.org/wiki/Ultraviolet 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 can be 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 {{val|6.075|e=27|u=watts}}, but due to the [https://en.wikipedia.org/wiki/Inverse-square_law inverse-square law], only about {{val|456|u=W/&NoBreak;m<sup>2</sup>}} reaches Avalon.
This value is known as the solar 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.

== Solar activity ==

Solakku generates a constant stream of charged particles at variable rates, known as solar wind, which makes up the corona. This solar 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 800 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. The complex magnetic fields formed as a result are usually the driving force of powerful events such as solar flares in lower-mass stars, 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 [https://en.wikipedia.org/wiki/Magnetic_reconnection 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 solar 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.

=== Effects ===

Solar wind is almost entirely warded off by the combined [https://en.wikipedia.org/wiki/Magnetosphere magnetospheres] of Avalon and Valaya, though these same fields may concentrate the charged particles received from the solar wind into [https://en.wikipedia.org/wiki/Van_Allen_radiation_belt 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 solar winds may reach the surface and chemically transform it, such as with the formation of [https://en.wikipedia.org/wiki/Tholin Tholins].

Avalon’s atmosphere, especially the ozone layer, is responsible for attenuating or even completely filtering the dangerous ultraviolet and X-Ray radiation of solar flares. Additionally, Valaya’s orbital inclination currently situates it and Avalon slightly away from Infernum’s orbital plane. The majority of energy released by these flares is thus only rarely aimed directly at it. This also true to varying degree for most planets within the Solakku system, with Magnus and Solvis being the most at risk.

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 solar winds, but interplanetary space possesses a dangerously high background radiation count caused by solar wind. Both computer systems and crewed modules aboard spacecraft traversing this space must thus be built to mitigate or block the effects of solar wind emissions.

Solar flares pose an acute danger within a specific area, aligned with Infernum’s orbital plane. If one strikes a spacecraft, it may cause electrical malfunctions on space probes and severe radiation exposure to lifeforms on crewed vessels, especially on closer orbits, such as around Solvis. The energies of solar flares are not inhibited by Solvis’ magnetosphere and can thus reach any spacecraft outside of its atmosphere.

However, the possible damage they 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’ solar activity as well, meaning they can easily protect against Solakku’s flares. Historically, however, solar wind and solar flares lead to major difficulties in non-FTL deep-space exploration.

= Life phases =

== Formation ==

Solakku formed approximately 2.6&nbsp;billion years ago through [https://en.wikipedia.org/wiki/Gravitational_collapse gravitational collapse] of a [https://en.wikipedia.org/wiki/Molecular_cloud 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 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.

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 [https://en.wikipedia.org/wiki/Protoplanetary_disk 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 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, solar winds from Solakku would’ve blown all remaining dust and gas away, completing the process. 

== Main Sequence ==

[[File:Hr diagramm solakku new.png|300px|thumb|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&nbsp;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 opaqueness 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&nbsp;to&nbsp;200&nbsp;million years.

{{clear}}

== 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&nbsp;{{Solar radius}} and 220&nbsp;{{Solar luminosity}}. At the same time, its temperature falls due to the increase in surface area, to as low as 4800&nbsp;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 incredibly 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 to deplete 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 [https://en.wikipedia.org/wiki/Helium_flash helium flash], from which point onwards it will fuse almost exclusively helium to carbon and oxygen using the [https://en.wikipedia.org/wiki/Triple-alpha_process 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&nbsp;K while its radius falls below 160&nbsp;{{Solar radius}}.

This helium-burning phase will last at least 300 million years, during which carbon and oxygen steadily accumulate in the core. Its 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 solar 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 [https://en.wikipedia.org/wiki/Asymptotic_giant_branch asymptotic giant phase], during which the star’s radius will rise to over 0.75&nbsp;AU, with an accompanying increase in luminosity to over 4000&nbsp;{{Solar luminosity}}.

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 they haven’t already. [[Magnus]] will be completely lost sometime during the asymptotic giant phase, when Solakku’s radius grows past the planet’s orbit.
However, [[Musoya]] 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&nbsp;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&nbsp;million years, these pulses rip away material from the outer layers of the star, shedding it into a [https://en.wikipedia.org/wiki/Planetary_nebula 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 [https://en.wikipedia.org/wiki/White_dwarf white dwarf], heating up to over {{val|100000|u=K|fmt=commas}} 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 =

[[File:Screenshot from 2025-06-03 17-58-11.png|thumb|Stars and star systems within 5&nbsp;light-years of Solakku.|500px]]

Solakku is situated relatively close to the galactic core, orbiting the galactic core at a distance of just around {{val|8200|u=light-years|fmt=commas}}. 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 {{val|15000|u=years|fmt=commas}} another star passes within 0.5&nbsp;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;nbsp;light-years in {{val|5000|u=years|fmt=commas}}.

The following table lists all known stars within a radius of 5&nbsp;light-years around Solakku. An interactive map is accessible [https://avalikin.wiki/interactive/star-map/star-map.html at this link].
Only the primary element of each system is shown.

{| {{Table}}
! Designation !! Distance (ly) !! Stellar class
|-
! Solakku
| 0
| style="background-color:#{{Color temperature|7803|hexval}}"|kA5hA8mF4
|-
! [[Karat]]
| 0.96
| style="background-color:#{{Color temperature|11730|hexval}}"|DA4.4
|-
! Wanderer
| 1.02
| style="background-color:#{{Color temperature|6888|hexval}}"|F2V
|-
! Ak-Vi
| 1.43
| style="background-color:#{{Color temperature|4378|hexval}}"|K6V
|-
! Arkut
| 1.89
| style="background-color:#{{Color temperature|9123|hexval}}"|A2V
|-
! ISC-233
| 2.41
| style="background-color:#{{Color temperature|1127|hexval}}"|T1.5
|-
! Thoje
| 2.51
| style="background-color:#{{Color temperature|6028|hexval}}"|G0V
|-
! Tsija’s Star
| 2.93
| style="background-color:#{{Color temperature|2789|hexval}}"|M7V
|-
! Rivalu
| 3.16
| style="background-color:#{{Color temperature|4377|hexval}}"|K6V
|-
! ISC-57
| 3.27
| style="background-color:#{{Color temperature|1722|hexval}}"|L4
|-
! 57 Sharu
| 3.34
| style="background-color:#{{Color temperature|2400|hexval}}"|M9V
|-
! Tarik 27-C
| 3.38
| style="background-color:#{{Color temperature|4222|hexval}}"|K7V
|-
! ISC-22
| 3.43
| style="background-color:#{{Color temperature|3070|hexval}}"|M5V
|-
! ISC-87
| 3.87
| style="background-color:#{{Color temperature|1922|hexval}}"|L2.5
|-
! ISC-89
| 4.05
| style="background-color:#{{Color temperature|828|hexval}}"|T6.5
|-
! ISC-168
| 4.20
| style="background-color:#{{Color temperature|4100|hexval}}"|K7V
|-
! Tarik 23
| 4.23
| style="background-color:#{{Color temperature|2690|hexval}}"|M7V
|-
! Evits 3
| 4.24
| style="background-color:#{{Color temperature|5788|hexval}}"|G2V
|-
! Evits 9
| 4.37
| style="background-color:#{{Color temperature|3567|hexval}}"|M2V
|-
! [[Amber Light]]
| 4.37
| style="background-color:#{{Color temperature|3689|hexval}}"|M1 III
|-
! Atsavara
| 4.45
| style="background-color:#{{Color temperature|6689|hexval}}"|F4V
|-
! Tarik 59
| 4.57
| style="background-color:#{{Color temperature|5180|hexval}}"|DZ11.8
|-
! Arakvus
| 4.95
| style="background-color:#{{Color temperature|9877|hexval}}"|A0V
|}

= Star system =

TODO: section on planetary system with relevant links to individual bodies

TODO: embed relevant links to wikipedia articles in text