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Every exoplanet was propagated with gmForParent(undefined) — the Sun's gravitational parameter — so the whole catalogue orbited as though each host were exactly one solar mass. Most hosts are red dwarfs far lighter than that, and a heavier central mass pulls harder and shortens the period, so their planets were whirling round much too fast: TRAPPIST-1 is 0.09 solar masses, and its planets were completing an orbit in roughly a third of the true time. pl_orbper was already in the TAP query and was being discarded on the way into the record. It is now kept, along with st_mass. A period and a semi-major axis together pin the host's gravitational parameter exactly, via GM = n^2 a^3 — no stellar model, no assumption, just the inverse of the orbitalPeriodDays helper that was already there. resolveGravitationalParameter picks the best available source: the measured period, else the published host mass, else one solar mass as before. A derived value implying something outside 0.01-150 solar masses is rejected and falls through, since a period and axis taken from disagreeing solutions would otherwise send a planet spinning at a visibly absurd rate. Note the direction of the error, which is the opposite of what it looks like: assuming a *heavier* host than reality makes a planet orbit *faster*. A test pins it, and caught me stating it backwards first. The NASA Exoplanet Archive is unreachable from this environment (egress policy returns 403 on CONNECT), so exoplanets.json cannot be regenerated here and still carries no periods. Behaviour is therefore unchanged until `npm run etl` is run somewhere with archive access, at which point every planet with a published period starts moving correctly with no further code changes. build.ts reports how many records gained a period, and rejects non-positive ones. Tests: 171 passing, up from 151, including a new end-to-end check that TRAPPIST-1 b with its real period completes exactly one orbit in 1.51088 days and sits a full diameter away at half that. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01WaySiNst4HhDXBHnMy8p5G
star-map
An interactive 3D star map in the spirit of Star Citizen's in-game starmap, but populated with real astronomical data instead of fictional systems. Browse the solar neighbourhood, fly into a star's system to see its planets on their real orbits, and drill into a single body for the NASA figures behind it.
This repo also hosts a small Claude Code plugin marketplace — see Plugins below.
Running it
npm install
npm start # dev server on http://localhost:4200
npm run build # production bundle into dist/
Requires the Node version in package.json's Angular toolchain range (Node 22.22.3+ or 24.15+).
npm test # unit/component tests (Vitest, jsdom)
npm run e2e # end-to-end tests (Playwright + Chromium) — see e2e/README.md
npm run etl # refresh the astronomical datasets — see below
npm run etl:typecheck # type-check the ETL scripts (they build separately from the app)
npm run e2e:typecheck
What's in it
Galaxy view — every HYG-catalogue star within 50 parsecs as instanced camera-facing billboards, positioned from real RA/Dec/parallax, coloured by spectral index and sized by magnitude. Names label the stars nearest the camera. Behind them sits a backdrop of notable deep-sky objects and a Milky Way panorama.
System view — selecting a star flies the camera continuously into its system rather than cutting to a new scene. The Sun gets the real solar-system bodies from JPL Horizons; other stars get their confirmed exoplanets. Orbits are drawn as ellipses and bodies are propagated along them by a Kepler solver against the current epoch.
Body detail — a dedicated close-up scene and info panel for one planet, moon or exoplanet, with real photography where NASA/ESA/USGS imagery exists.
Search — name search across stars, solar-system bodies and exoplanets, navigating to the same place an in-scene click would.
Architecture notes
- Rendering runs on Three.js
WebGPURenderer, which falls back to a WebGL2 backend automatically. The render loop runs outside Angular's change detection. - Stars are billboards, not points. The WebGPU backend caps point primitives at a single
pixel, so a points cloud renders every star as an identical dot regardless of magnitude. The
star field is instanced quads on a
SpriteNodeMaterialinstead, which behaves the same on both backends. Their size is angular rather than world-space — real stars are unresolvable point sources, so apparent size should follow brightness, not distance. - Two coordinate scales. The galaxy view works in parsecs and the system view in AU — about eight orders of magnitude apart, which wrecks float precision if rendered in one unit space. The camera rig recentres the active star to the origin ("floating origin") and swaps the unit scale and near/far planes at the transition point.
- No backend. Every dataset is baked at build time into
src/assets/data/and served as a static asset. Nothing queries an astronomy API at runtime.
Data pipeline
npm run etl runs tools/etl/build.ts, which fetches each source, writes the static assets,
then validates the combined output. Raw responses are cached under tools/etl/.cache/, so
re-runs are cheap and offline-friendly; set ETL_FORCE_REFRESH=1 to bypass the cache.
| Script | Source | Output |
|---|---|---|
fetchStars.ts |
HYG database (Hipparcos/Yale/Gliese) | stars.bin, stars-index.json |
fetchSolarSystem.ts |
JPL Horizons / SSD | bodies.json |
fetchExoplanets.ts |
NASA Exoplanet Archive (TAP) | exoplanets.json |
fetchDeepSky.ts |
OpenNGC | deepsky.json |
Star positions ship as a packed Float32Array (stars.bin) rather than JSON to keep the
initial payload and parse cost down; stars-index.json carries everything else in the same
order.
ETL_STAR_DISTANCE_PC (default 50) sets the star-field distance cutoff.
On deep-sky distances
OpenNGC publishes no distance column, so distance has to be inferred — and the inference fails for precisely the best-known objects. M31, M33 and M42 are Local Group members whose redshift is negative or absent, and the catalogue's parallax for a galaxy comes from a cross-matched foreground star (it lists 6 mas for M31, implying 167 pc for something 780,000 pc away).
So deep-sky records store a unit direction on the celestial sphere rather than a position:
the line of sight is always known precisely, and the objects are drawn as a fixed-radius
backdrop shell where true distance would be unusable anyway. distancePc is optional metadata,
derived from parallax for galactic objects or the Hubble law for genuinely distant galaxies,
and left null — with its distanceMethod — whenever neither is trustworthy. Roughly 330 of
the 463 cataloged objects get a distance; the rest honestly report none.
Layout
src/app/
core/engine/ Three.js renderer, render loop, resize
core/data/ static-asset loading and caching
features/galaxy-system/ shared galaxy+system scene, camera rig, star field,
deep-sky backdrop, orbits, labels
features/body-detail/ close-up scene and info panel
features/search/ name search across every dataset
shared/astro/ coordinates, Kepler propagator, deep-sky classification
shared/models/ record contracts shared by the app and the ETL
shared/rendering/ skybox, glow sprites, texture catalog
shared/state/ navigation store (Angular signals)
tools/etl/ build-time data pipeline
e2e/ Playwright end-to-end tests
The design document behind all of this is .junie/plans/nasa-star-map.md.
Plugins
This repo doubles as a Claude Code plugin marketplace. Adding it and installing a plugin defaults to user scope, meaning the plugin becomes available in every project on your machine, not just the one you happen to be in:
/plugin marketplace add avalon-vanguard/star-map
/plugin install caveman@star-map
Scope can be overridden at install time if you want it tied to a single repo instead:
# Shared with collaborators via that repo's .claude/settings.json
/plugin install caveman@star-map --scope project
# Just for you, in that one repo only (gitignored)
/plugin install caveman@star-map --scope local
See Claude Code plugin installation scopes
for details on user / project / local scope.
- caveman —
/cs:cavemanultra-compressed communication mode.- Command:
commands/cs/caveman.md - Agent:
agents/cs-caveman-mode.md - Skill:
skills/caveman/SKILL.md
- Command:
Data credits
Star catalogue: HYG database (Hipparcos, Yale
Bright Star, Gliese). Solar-system ephemerides: NASA/JPL Horizons. Exoplanets: NASA Exoplanet
Archive. Deep-sky objects: OpenNGC. Body and skybox
imagery: NASA/JPL/USGS public domain and Solar System Scope (CC BY 4.0) — per-file provenance
is recorded in src/app/shared/rendering/texture-catalog.ts.