View source for Star types

{{WIP}}

[[Starship Simulator]] features a diverse range of star types within its procedurally generated [[Milky Way]] galaxy, based on the real-world '''stellar classification''' system and astrophysical principles. The type of star significantly influences the formation, characteristics, and potential habitability of its surrounding planetary system, as well as how it appears visually and on [[Sensors]]. The game generates main sequence stars (O, B, A, F, G, K, M), brown dwarfs (L, T, Y), and stellar remnants (White Dwarfs, Neutron Stars, Black Holes). Groundwork for other types like T-Tauri and Wolf-Rayet stars has also been implemented.

== Stellar Classification ==
The game uses the standard '''OBAFGKM''' spectral sequence for main-sequence stars, ordered from hottest (O) to coolest (M), along with '''L''', '''T''', and '''Y''' classes for brown dwarfs. This sequence primarily indicates the star's surface temperature.

To provide more detail, the full classification adds a number (0-9) and a Roman numeral (I-VII):
*'''Number (0-9):''' This digit subdivides each spectral class, indicating temperature within that class. '''0''' is the hottest sub-type, and '''9''' is the coolest. For example, a G0 star is hotter than a G2 star, which is hotter than a G9 star.
*'''Roman Numeral (Luminosity Class):''' This indicates the star's size and evolutionary stage, relating to its intrinsic brightness. Common classes are:
** '''V:''' Main Sequence (Dwarf stars) - Actively fusing hydrogen in their core (e.g., [[Sol]] is G2'''V''').
** '''IV:''' Subgiant - Starting to evolve off the main sequence.
** '''III:''' Giant - Evolved, larger stars.
** '''II:''' Bright Giant.
** '''I:''' Supergiant (often subdivided into Ia, Iab, Ib) - Very large, luminous, massive stars.
** '''VI / sd:''' Subdwarf.
** '''VII / D:''' White Dwarf (stellar remnant).

''A common [[wikipedia:Stellar_classification#Mnemonics|mnemonic]] used to remember the main sequence order (O, B, A, F, G, K, M) is "'''O'''h, '''B'''e '''A''' '''F'''ine '''G'''irl/'''G'''uy, '''K'''iss '''M'''e!". Extensions sometimes include the brown dwarf classes: "...Kiss '''M'''e, '''L'''ovingly, '''T'''oday, '''Y'''ay!".''

[[Dev Builds|Development Build 0.225.0.30]] introduced support for 80 stellar sub-classes within the game, ranging from O0V (~50,000 K) down to Y9 (~250 K), allowing for these finer distinctions within each major class.

== Main Sequence Stars ==
These are stars in the main phase of their life cycle (Luminosity Class '''V'''), actively fusing hydrogen into helium in their cores. They represent the vast majority of stars observed.

=== O-Type ===
* '''Colour:''' Blue-Violet
* '''Temperature:''' > 30,000 K (O0V ~50,000 K)
* '''Mass / Luminosity:''' Highest mass (> 16 M☉) and extremely luminous (thousands of times brighter than Sol).
* '''Lifespan:''' Very short (millions of years).
* '''Commonality:''' Extremely rare (< 0.0001%).
* '''Location:''' Found almost exclusively in active star-forming regions (Open Clusters) within the Thin Disc's spiral arms.
* '''System Notes:''' Intense ultraviolet radiation and powerful stellar winds make close-in habitability virtually impossible. Their short lives often preclude the development of complex life. Systems may have fewer rocky planets due to potentially lower initial metallicity in some formation regions, or planets may be stripped of atmospheres. Often end their lives in supernovae, potentially forming Neutron Stars or Black Holes.

=== B-Type ===
* '''Colour:''' Blue-White
* '''Temperature:''' 10,000 K - 30,000 K
* '''Mass / Luminosity:''' High mass (2 - 16 M☉) and very luminous.
* '''Lifespan:''' Short (tens to hundreds of millions of years).
* '''Commonality:''' Rare (~0.1%).
* '''Location:''' Predominantly found in younger regions of the Thin Disc arms, often associated with O-type stars.
* '''System Notes:''' High radiation levels still pose challenges for close-in habitability. Likely to host gas giants and potentially some rocky worlds if metallicity allows. End life as White Dwarfs or potentially via supernova for the most massive examples.

=== A-Type ===
* '''Colour:''' White
* '''Temperature:''' 7,500 K - 10,000 K
* '''Mass / Luminosity:''' Moderately high mass (~1.4 - 2 M☉), significantly brighter than Sol.
* '''Lifespan:''' Moderately short (hundreds of millions to ~1 billion years).
* '''Commonality:''' Uncommon (~0.6%).
* '''Location:''' Common throughout the Thin Disc.
* '''System Notes:''' [[Habitable Zone]] is wider and further out than Sol's. Planets may form readily, but the star's lifespan is shorter than Sol's, potentially limiting complex life evolution time. End life as White Dwarfs. Sirius is a notable real-world example.

=== F-Type ===
* '''Colour:''' Yellow-White
* '''Temperature:''' 6,000 K - 7,500 K
* '''Mass / Luminosity:''' Slightly more massive than Sol (~1.0 - 1.4 M☉), brighter than Sol.
* '''Lifespan:''' Long (few billion years).
* '''Commonality:''' Common (~3%).
* '''Location:''' Abundant throughout the Thin Disc.
* '''System Notes:''' Considered good candidates for habitable planets, with habitable zones slightly further out than Sol's. Offer a long stable period for potential life development. End life as White Dwarfs. Polaris (the North Star) is an example.

=== G-Type ===
* '''Colour:''' Yellow
* '''Temperature:''' 5,200 K - 6,000 K
* '''Mass / Luminosity:''' Sol-like mass (~0.8 - 1.0 M☉) and luminosity.
* '''Lifespan:''' Very long (~10 billion years).
* '''Commonality:''' Fairly common (~7.6%).
* '''Location:''' Abundant throughout the Thin Disc.
* '''System Notes:''' Considered prime candidates for Earth-like worlds due to stable energy output and long lifespans. Earth's [[Sol]] (G2V) is the benchmark. The [[Habitable Zone]] is well-defined. End life as White Dwarfs.

=== K-Type ===
* '''Colour:''' Orange
* '''Temperature:''' 3,700 K - 5,200 K
* '''Mass / Luminosity:''' Less massive than Sol (~0.45 - 0.8 M☉), dimmer than Sol.
* '''Lifespan:''' Extremely long (tens of billions of years).
* '''Commonality:''' Very common (~12%).
* '''Location:''' Found throughout the galaxy, including older populations in the Thick Disc and Bulge.
* '''System Notes:''' [[Habitable Zone]] is closer to the star, increasing the likelihood of planets being tidally locked. Lower UV radiation but potentially higher flare activity compared to G-types. Their extremely long lifespans offer vast timescales for life to potentially develop. End life as White Dwarfs (eventually). Arcturus is an example.

=== M-Type ===
* '''Colour:''' Red
* '''Temperature:''' < 3,700 K
* '''Mass / Luminosity:''' Low mass (~0.08 - 0.45 M☉), very dim.
* '''Lifespan:''' Exceptionally long (trillions of years).
* '''Commonality:''' Most common type of star (~76%).
* '''Location:''' Ubiquitous across all galactic regions and populations.
* '''System Notes:''' [[Habitable Zone]] is very close, making planets highly susceptible to tidal locking and intense stellar flare activity, which may challenge surface habitability despite the star's longevity. Form predominantly rocky planets if metallicity permits. Visibility from the [[Bridge]] window was toned down in dev builds for realism. Proxima Centauri is a nearby example. Will eventually become White Dwarfs after potentially trillions of years.

== Brown Dwarfs ==
Sub-stellar objects lacking sufficient mass to ignite sustained hydrogen fusion. They represent a link between the smallest stars and the largest planets. Groundwork added in Build 0.225.0.16, implementation in Build 0.225.0.25.

=== L-Type ===
* '''Temperature:''' ~1,300 K - ~2,400 K
* '''Characteristics:''' Formed like stars but never achieved stable fusion. Emit primarily in infrared. Hotter than T-types, may show lithium lines in spectra.
* '''Notes:''' Very dim visually. Holo display colour clamped in-game (Build 0.225.0.49) and low visibility from bridge (Build 0.225.0.66).

=== T-Type ===
* '''Temperature:''' ~700 K - ~1,300 K
* '''Characteristics:''' Cooler than L-types, with methane absorption bands prominent in their spectra, distinguishing them from M-type stars. Sometimes described as having a magenta appearance in-game (Build 0.225.0.26).
* '''Notes:''' Extremely dim visually, emit mostly infrared. Low visibility and adjusted holo display colour in-game.

=== Y-Type ===
* '''Temperature:''' < ~700 K (down to ~250 K for Y9)
* '''Characteristics:''' The coolest category of star-like objects, essentially failed stars or giant planets radiating remnant heat. Water ice clouds may form in their atmospheres.
* '''Notes:''' Emit almost entirely in infrared. Very difficult to detect. Low visibility and adjusted holo display colour in-game.

== Stellar Remnants ==
The compact objects left behind after stars exhaust their nuclear fuel and cease fusion.

=== White Dwarf ===
* '''Luminosity Class:''' VII or D
* '''Characteristics:''' The dense (~Earth-sized, ~0.6 Solar mass) remnant core of a low-to-medium mass star (like types A through M). Extremely hot initially, but cools slowly over billions of years as it radiates stored thermal energy. Composed mostly of carbon and oxygen.
* '''Notes:''' Data for millions of real white dwarfs included in the game's stellar database (Build 0.225.0.27).

=== Neutron Star ===
* '''Characteristics:''' An incredibly dense object (~city-sized, ~1.4-2 Solar masses) composed almost entirely of neutrons, supported by neutron degeneracy pressure. Formed during the supernova of a massive star not quite massive enough to become a black hole. Often possess extremely strong magnetic fields and rapid rotation (pulsars).
* '''Notes:''' Groundwork for implementation added (Build 0.225.0.16).

=== Black Hole ===
* '''Characteristics:''' An object with gravity so intense that nothing, not even light, can escape from within its event horizon. Formed from the collapse of the most massive stars or through galactic center processes ([[Sagittarius A*]]). Defined by mass, spin, and charge.
* '''Notes:''' Groundwork added (Build 0.225.0.16). Specific behaviour refined in-game including mass ranges, radii, and surrounding planets (tend to be icy due to immense Roche limits) (Build 0.225.0.31). Holo display rendering fixed (Build 0.225.0.44).

== Other Types ==
Groundwork has been laid for additional stellar or sub-stellar objects, indicating they are planned features:
* '''T-Tauri Stars:''' Pre-main-sequence stars, representing a very early stage in stellar evolution before stable hydrogen fusion begins. Often variable and associated with strong stellar winds and accretion disks.
* '''Wolf-Rayet Stars:''' Very massive, hot stars nearing the end of their lives, characterized by powerful stellar winds that strip away their outer hydrogen layers, revealing helium and heavier elements. Precursors to some types of supernovae.
* '''Rogue Planets:''' Planetary-mass objects that have been ejected from their original star systems and drift freely through interstellar space.

== In-Game Significance ==
A star's type directly impacts multiple aspects of gameplay and exploration:
* '''Visuals & Sensors:''' Determines the star's appearance, colour, and spectral signature, affecting visual identification and [[Sensors]] readings (including UI colour coding and spectral analysis graphics). The full classification (e.g., G2V) provides more detailed information.
* '''System Environment:''' Dictates the [[Habitable Zone]] location, radiation levels, and overall energy environment of a star system.
* '''Planet Formation:''' Influences the types and composition (metallicity) of planets likely to be found orbiting the star.
* '''Life Potential:''' Star type, age, and stability are key factors in the procedural generation of life and civilizations.
* '''Navigation & Hazards:''' May affect [[Alcubierre Drive|FTL]] travel near the star or present specific environmental hazards (e.g., radiation, flares, extreme gravity near remnants).

[[Category:Stars]]
[[Category:Galaxy Generation]]