Galaxy Generation

Galaxy Generation, Stellar Aging & Validation

Cosmos Genesis generates complete galaxies — from morphological structure to individual star systems, stellar lifecycles, and planetary habitability — using a multi-phase distributed pipeline grounded in peer-reviewed astrophysics. Generation runs may be followed by an on-demand physics validation suite, triggered manually from the Validation panel, that measures accuracy against published benchmarks.

Deterministically random. Every generation run is fully reproducible: all star positions, masses, orbital elements, cluster memberships, and physics properties are derived from a single integer seed via a deterministic . Providing the same seed and galaxy name always produces bit-for-bit identical output.

Public reference. This page explains what Cosmos Genesis does and the science it's based on. Implementation details, such as exact algorithms, tuning values and infrastructure, are kept in our internal documentation.

Generation Pipeline

A ten-phase distributed pipeline produces a physically accurate stellar population for galaxies at any scale, with results streamed to the galaxy explorer while generation is still running.

Every star system is spatially indexed at generation time to sub-parsec resolution, so proximity queries — nearby stars, nearest object, blast-radius lookups — touch only the relevant local region rather than scanning the full galaxy. The same spatial index underlies both the physics simulation and the GPU-streamed tile layout.

The phases below each list the scientific claim made, the published standard it follows, and the measurable output or threshold that validates it.

Phase 0

Galaxy Morphology

The pipeline begins by writing a single galaxy record and computing all morphology parameters. A morphological class (spiral, elliptical, lenticular, or irregular) is assigned1 and the resonance structure governing all subsequent phases is derived from the rotation curve. Spiral galaxies receive inner and outer Lindblad resonances and a corotation radius.2 Disk ellipticity is seeded deterministically from the galaxy name and seed, ensuring reproducible geometry across pipeline runs. Galaxy status is set to generating for the remainder of the pipeline run.

Claims & Measurements

Morphological typesSpiral · Elliptical · Lenticular · Irregular
Resonance outputsInner Lindblad resonance, outer Lindblad resonance, corotation radius
Determinism guaranteeAll downstream phases are fully deterministic from seed + galaxy name

Phase 1

Star Systems

The largest phase: each star system is assigned a mass drawn from the Kroupa (2001)3 initial mass function, a stellar age drawn from an exponentially declining star-formation history consistent with the Milky Way's known star-formation timeline, and a 3D position from the galaxy's morphology density profile with a radially declining metallicity gradient consistent with observed abundance gradients. Evolutionary stage, luminosity, radius, and effective temperature are computed from those ages using published stellar evolution thresholds (Hurley 2000)4. Habitable zone boundaries, asteroseismic frequencies, binary companions (~45% of systems), radiation zones, and EM signatures are all written in this phase.

Claims & Measurements

IMF modelKroupa (2001)3 broken power-law initial mass function
Star formation historyExponentially declining SFH consistent with the Milky Way star-formation timeline
Metallicity gradientRadially declining, consistent with observed Milky Way abundance gradients
Habitable zone modelKopparapu et al. (2013)5 stellar flux limits
Stellar seismologyAsteroseismic oscillation frequencies — Kjeldsen & Bedding (1995)6
Binary fraction~45 % of systems with companions; ~5 % trinary; orbital periods from Kepler's Third Law

Phase 2

Many-body gravity (N-body) Relaxation

Analytical initial conditions produce unphysical velocity distributions. Phase 2 corrects this with an N-body relaxation step7 that brings the stellar velocity distribution into dynamical equilibrium before positions are finalized.8 Toomre Q velocity dispersions (σ_R, σ_θ, σ_z) are then layered on top using profiles calibrated to observed disk kinematics. Running this step early — immediately after star placement — means Phase 3 can publish velocity-accurate tiles for GPU streaming without waiting for the full pipeline.

Claims & Measurements

Equilibration targetVirial equilibrium — |2T/W + 1| < 5 % convergence criterion
Toomre Q dispersionsRadial, azimuthal, and vertical velocity dispersions calibrated to observed disk-galaxy kinematics

Phase 3

Tile Export

Phase 3 backfills Phase 2 equilibrium velocities into the star system records and immediately publishes precomputed star-field tiles for GPU-accelerated streaming. Moving tile export here — before clusters, stellar death, and planetary generation — means the frontend can begin star field streaming while the remaining phases are still running.

Claims & Measurements

AvailabilityTiles published at ~50 % pipeline completion, not end

Phase 4

Star Clusters

Open and globular clusters are generated with masses, ages, core radii, tidal radii, velocity dispersions, and metallicities derived from empirical distributions. Each star system that falls within a cluster's tidal radius is linked to that cluster. Cluster types include OPEN, GLOBULAR, SUPER_STAR_CLUSTER, and STELLAR_ASSOCIATION, with generation-type–aware population scaling.

Claims & Measurements

Open cluster mass range300 – 10⁵ M☉ (log-uniform)
Globular cluster mass range10⁴ – 10⁷ M☉ (log-uniform)
Tidal radius modelKing-model empirical ratio from core radius

Phase 5

Stellar Death & Atmospheric Effects

Stars that have exceeded 1.5× their main-sequence lifetime4 are assigned a remnant type — white dwarf (M < 8 M☉, Kalirai 20089 initial-final mass relation (IFMR)), neutron star (8–25 M☉), or black hole (M ≥ 25 M☉, Fryer 2012 rapid mechanism). NS progenitors produce supernovae; 30% of neutron stars become pulsars and 5% become magnetars (mutually exclusive). Black hole hypernovae produce gamma-ray bursts at 5% on-axis probability. Atmospheric damage from each event propagates to every planetary system within its blast or lethal radius. Recent events also write supernova remnants and planetary nebulae.

Claims & Measurements

Remnant accuracy> 99 % correct per standard stellar evolution mass thresholds
SN blast radiusScales with progenitor mass — calibrated to Chevalier (1982)10 supernova remnant models
Ionization radius0.5–5 LY for planetary nebulae
Backpropagation accuracy≥ 99.9 % damage severity correct; all affected systems within radius

Phase 6

Planetary Systems

Planets are assigned to every non-remnant star system: planet count follows a distribution consistent with observed Kepler multi-planet systems (Borucki et al. 2011)11, semi-major axes span log-space lane assignments with Gaussian jitter, and the Weiss & Marcy (2014)12 mass-radius relation determines radii. Tidal locking, equilibrium temperature, and eccentricity are computed per planet. Gas giants receive moons (up to 20), magnetospheres with radiation belts, and decametric EM signatures. Phase 3 atmosphere damage is merged into affected planetary systems at write time.

Claims & Measurements

Planet count modelLog-normal count distribution consistent with observed Kepler multi-planet systems — Borucki et al. (2011)11
Mass-radius relationPiecewise power-law — Weiss & Marcy (2014)12
Magnetosphere modelMagnetosphere strength for gas giants calibrated against solar-system analogs (Earth, Jupiter)

Phase 7

Small Bodies

Protoplanetary disks are generated for young stars whose age falls below a mass-dependent disk lifetime threshold consistent with observed T Tauri disk survival times (Hartmann et al. 1998)13. Asteroid belts (main belt at 0.4–0.9× snow line, Kuiper analog at 30–100 astronomical units (AU)) and Oort clouds (inner 2000–5000 AU, outer 50 000–200 000 AU) are added probabilistically to older systems. Comets are generated per Oort-cloud system with isotropic inclinations and perihelion passages inside 5 AU.

Claims & Measurements

Disk lifetimeMass-dependent threshold consistent with observed T Tauri disk lifetimes — Hartmann et al. (1998)13
Oort cloud boundariesInner 2 000–5 000 AU; outer 50 000–200 000 AU

Phase 8

Interstellar medium (ISM) Phenomena

Interstellar medium objects complete the galaxy. Dust clouds span four morphological classes (DIFFUSE, BOK_GLOBULE, DARK_NEBULA, REFLECTION_NEBULA) with triaxial ellipsoid geometry and MRN grain distributions. Molecular clouds use the Schmidt-Kennicutt star-formation rate relation.14 HII regions receive Strömgren radii computed from ionizing photon flux. Active galactic nuclei (15–30% of galaxies) are assigned Eddington fractions, active galactic nucleus (AGN) classes (Seyfert 1/2, LINER, Blazar), and optionally relativistic jet pairs. Cosmic strings are placed at 0.1% probability per galaxy.

Claims & Measurements

Molecular cloud star formation rate (SFR)Schmidt-Kennicutt: Σ_SFR ∝ Σ_gas^1.4
HII region radiusStrömgren sphere: R_s = (3Q_ion / 4π α_B n_e²)^(1/3)
AGN probability15–30 % of full galaxies; M_BH from M–σ proxy

Phase 9

Output & Finalization

Phase 9 finalizes galaxy status from GENERATING to COMPLETE, embeds final record counts in performance metrics, and publishes a compressed visualization summary for fast client-side galaxy rendering. Tile export completed in Phase 3, so tiles are already live.

Claims & Measurements

Galaxy status updateGENERATING → COMPLETE
Client artifactsCompressed visualization summary and tile manifest (tiles written in Phase 3)

Stellar Evolution

Each star's current evolutionary state is computed during Phase 1 using its SFH-assigned age and published stellar physics formulas — no separate post-processing pass is required. The pipeline computes the full evolutionary lifecycle position for every star at generation time.

Lifecycle Stages

Main Sequence→Subgiant→Red Giant→Asymptotic giant branch (AGB)→White Dwarf→Neutron Star→Black Hole

Stage Progression (age relative to main-sequence lifetime)

  • →Main Sequence — hydrogen core fusion; lifetime set by stellar mass4
  • →Subgiant Branch — post-main-sequence expansion begins
  • →Red Giant Branch — envelope expansion and increased luminosity
  • →Asymptotic Giant Branch — advanced giant-phase evolution
  • →Remnants — end state assigned by progenitor mass (see Stellar Death, Phase 5)

Properties Derived from Age & Mass

  • →Luminosity — derived from stellar mass via the empirical mass-luminosity relation for main-sequence stars4
  • →Radius and effective temperature — derived from luminosity via the Stefan-Boltzmann law
  • →Mass loss — stellar wind calibrated to Vink et al. (2001)15 for massive stars
  • →Stellar rotation — slows over time via magnetic braking, consistent with observed spin-down of main-sequence stars

Generation Validation Suite

Five physics validators run on demand via the Validation panel. Each produces a PASS / WARN / FAIL status against a published benchmark. Overall generation PASS requires the three critical validators to pass.

The chi-square goodness-of-fit on the initial mass function (IMF validator) is the primary measurable accuracy claim: it directly tests whether the generated spectral-type frequency distribution matches observations across seven stellar classes.

ValidatorWhat We CheckPublished Benchmark
Initial mass function (IMF)critical
Chi-square goodness-of-fit vs. Kroupa (2001)3 spectral type distribution across seven stellar classesM-type 70 %, O-type 0.5 %
Age Distributioncritical
Chi-square on stellar age bins against an exponentially declining star-formation history consistent with the Milky Way's known timeline4 age bins vs. observed Milky Way star formation history (SFH)
Physical Correlationscritical
Pearson r on log(mass) vs. log(luminosity) and log(mass) vs. log(radius) for main-sequence stars; age-feature correlations (protoplanetary disks vs. system age)Mass–luminosity r > 0.85; Mass–radius r > 0.85
Stellar Death
Supernova rate per century, blast and ionization radii, progenitor mass → remnant class mapping (white dwarf / neutron star / black hole)SN rate 1–3 / century16 (Tammann et al. 1994)17; remnant types > 99 % correct
Backpropagation
Distance-dependent atmosphere loss from supernova and GRB events; damage severity thresholds; all affected systems within blast or lethal radius≥ 99.9 % damage severity correct; all affected systems within radius

Overall PASS requires all four critical checks to pass: IMF, Age Distribution, and the two Physical Correlations sub-checks (mass–luminosity and mass–radius). Stellar Death and Backpropagation may produce WARN without failing the generation run.

Full Reference List

All physics models are grounded in or validated against published peer-reviewed literature. Reviewers can independently verify each methodology from the citations below.

  1. 1.de Vaucouleurs (1959) — Classification and morphology of external galaxies — Handbuch der Physik 53 ↩
  2. 2.Binney & Tremaine (1987, 2008) — Galactic Dynamics — Princeton University Press ↩
  3. 3.Kroupa (2001) — Variation of the initial mass function — MNRAS 322:231 ↩
  4. 4.Hurley et al. (2000) — Comprehensive analytic formulae for stellar evolution — MNRAS 315:543 ↩
  5. 5.Kopparapu (2013) — Habitable zones around main-sequence stars — Astrophysical Journal Letters 765 ↩
  6. 6.Kjeldsen & Bedding (1995) — Amplitudes of stellar oscillations — Astronomy & Astrophysics 293 ↩
  7. 7.Aarseth (2003) — Gravitational N-body simulations — Cambridge University Press ↩
  8. 8.Heggie & Hut (2003) — The Gravitational Million-Body Problem — Cambridge University Press ↩
  9. 9.Kalirai et al. (2008) — The initial-final mass relationship — Astrophysical Journal 676 ↩
  10. 10.Chevalier (1982) — Self-similar solutions for the interaction of stellar ejecta with an external medium — ApJ 258 ↩
  11. 11.Borucki et al. (2011) — Characteristics of planetary candidates from Kepler — Astrophysical Journal 736 ↩
  12. 12.Weiss & Marcy (2014) — The mass-radius relation for 65 exoplanets smaller than 4 Earth radii — Astrophysical Journal Letters 783 ↩
  13. 13.Hartmann et al. (1998) — Accretion and the evolution of T Tauri disks — Astrophysical Journal 495 ↩
  14. 14.Kennicutt (1998) — The global Schmidt law in star-forming galaxies — Astrophysical Journal 498 ↩
  15. 15.Vink et al. (2001) — Mass-loss rates of very luminous massive stars — Astronomy & Astrophysics 369 ↩
  16. 16.Li et al. (2011) — Nearby supernova rates from the Lick Observatory Supernova Search — MNRAS 412 ↩
  17. 17.Tammann et al. (1994) — Supernova statistics and rates — Astrophysical Journal Supplement 92 ↩
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