Senrokai
d7e8ea1d4d
Add star-map Angular app, ETL pipeline, and caveman plugin Angular 3D star map (galaxy/system/body views, Three.js rendering, navigation store) plus the NASA ETL tooling that builds the star, exoplanet and solar-system datasets, Playwright e2e suite, and the cs:caveman Claude Code plugin (command, agent, skill). Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com> @
53 lines
2.2 KiB
TypeScript
53 lines
2.2 KiB
TypeScript
/** Astronomical unit conversion and gravitational constants shared by the astro math modules. */
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/** Number of astronomical units in one parsec (IAU exact definition). */
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export const AU_PER_PARSEC = 206264.80624709636;
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/**
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* Reference epoch (Julian date, J2000.0) used when orbital data lacks an explicit epoch —
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* e.g. exoplanets from the NASA Exoplanet Archive only report a handful of elements
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* (semi-major axis, eccentricity, sometimes argument of periapsis), not a mean-anomaly/epoch
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* pair. Defaulting the missing epoch to J2000 still lets the body's real orbital period
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* carry it around a plausible (if not phase-accurate) orbit over time.
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*/
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export const DEFAULT_EPOCH_JD = 2451545.0;
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/**
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* Heliocentric gravitational parameter (GM of the Sun), in AU^3/day^2 — the square of the
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* Gaussian gravitational constant `k = 0.01720209895 rad/day`. Used to derive a body's mean
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* motion from its semi-major axis via Kepler's third law.
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*/
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export const GM_SUN_AU3_PER_DAY2 = 0.01720209895 * 0.01720209895;
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/**
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* Approximate planet/Sun mass ratios for the major planets that host moons in `bodies.json`.
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* Used to derive each planet's gravitational parameter (for propagating its moons) as
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* `GM_SUN_AU3_PER_DAY2 * massRatio`. Precise enough for visualization; not JPL-grade.
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*/
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const PLANET_TO_SUN_MASS_RATIO: Record<string, number> = {
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earth: 3.003e-6,
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mars: 3.227e-7,
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jupiter: 9.545e-4,
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saturn: 2.857e-4,
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uranus: 4.365e-5,
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neptune: 5.151e-5
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};
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/**
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* Gravitational parameter (AU^3/day^2) to use when propagating a body's orbit: the Sun's
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* for planets/dwarfs/exoplanets, or the host planet's (derived from its Sun mass ratio) for
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* moons. Falls back to the Sun's GM if `parentBodyId` isn't a known planet.
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*/
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export function gmForParent(parentBodyId: string | undefined): number {
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if (!parentBodyId) {
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return GM_SUN_AU3_PER_DAY2;
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}
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const massRatio = PLANET_TO_SUN_MASS_RATIO[parentBodyId];
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return massRatio ? GM_SUN_AU3_PER_DAY2 * massRatio : GM_SUN_AU3_PER_DAY2;
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}
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/** Converts a JS `Date` into a Julian date (days), for driving the Kepler propagator "now". */
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export function dateToJulianDate(date: Date = new Date()): number {
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return date.getTime() / 86400000 + 2440587.5;
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}
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