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Match exoplanet hosts on the sky, at both epochs the archive might mean

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The host cross-reference matched in 3D, nearest star within half a parsec.
That is the wrong space for the same reason the star merge learned it: a
direction is measured, a distance is inferred. At 170 pc half a parsec is a
ten-arcminute cone, wide enough to hand the planets of stars our catalogue
does not carry to whatever bright star floats nearest — HATS-6 b sat on
HD 39500, seventy arcseconds away. At 60 pc it is tighter than the routine
disagreement between the archive's Hipparcos distances and our Gaia ones,
which is how four bright giants (7 CMa, HD 81688, omi UMa, xi Aql) lost
their planets and GJ 15 A's landed on a neighbouring entry.

Hosts are now resolved like stars are merged: by name first, then the
nearest star on the sky within a transverse budget — angle times the
archive's distance, 0.01 pc — whose distance does not flatly contradict the
archive's (the merge's own 50 % ratio). The budget is transverse because the
dominant error is proper motion over an epoch difference, a physical
displacement that is the same in parsecs at every distance: as an angle it
is 60" for Proxima and 2" for a host at 100 pc. Measured on the 504 hosts
whose archive name matches a catalogue name outright, true pairs reach
3.4e-3 pc; shifting every host a quarter of a degree finds nothing else
within 0.01 but Proxima's own entry, whose budget at 1.3 pc is wider than
the shift.

The archive never says which epoch a position is for, and they are mixed:
alf Tau and GJ 273 publish J2000, HD 133131 and TOI-2459 publish Gaia's
J2016. So the query asks for sy_pmra/sy_pmdec too, tries each position at
both ends of those sixteen years, and judges a star on whichever is closer.
Guess one epoch and a fast star's planets land on a companion: J2016 puts
Aldebaran's on Gl 171.1B, J2000 puts GJ 15 A's on a Gaia entry 15.9" out.

1 972 of 6 354 planets now sit on a host, 1 548 before: 432 gained, 26 on a
better star (GJ 15 A to Groombridge 34, GJ 676 A off its companion,
HD 19994 to 94 Cet), 8 lost — six false 3D matches to stars the catalogue
never contained, and GJ 273 b/c, whose archive row says 5.92 pc for
Luyten's Star at 3.79: a distance in flat contradiction is exactly what the
ratio guard exists to refuse, and the number to fix is upstream.

The 2 pc "rematch" apparatus is gone. build.ts recomputed every match after
fetchExoplanets had already written the file — at a different tolerance, so
the log reported a match count the data did not contain — and the offline
entry point that persisted it had no caller. One matcher, one set of
constants, used once. The archive cache is now keyed by a hash of the TAP
query, so a response cached before the proper-motion columns cannot serve
rows without them, where a missing cell would quietly read as "does not
move"; the row's astrometry is stored with each planet, which is what made
these tolerances measurable offline in the first place.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016jxMkwA2rbicdGxHosecYi
This commit is contained in:
Senrokai
2026-09-09 14:14:05 +02:00
co-authored by Claude Fable 5
parent dc2ce08694
commit 080bbe16dc
8 changed files with 198 additions and 238 deletions
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src/app/shared/astro/host-star-matching.spec.ts
+95 -29
View File
@@ -1,9 +1,14 @@
import { describe, expect, it } from 'vitest';
import { buildStarNameIndex, normalizeStarName, resolveHostStarId } from './host-star-matching';
import { propagateProperMotion, raDegDecDistanceToXyz } from './coordinates';
import { StarRecord } from '../models/star.model';
// A small fixture standing in for a slice of the HYG star index, used to exercise the
function star(id: number, name: string, raDeg: number, decDeg: number, distancePc: number): StarRecord {
return { id, name, ...raDegDecDistanceToXyz(raDeg, decDeg, distancePc), magnitude: 10, spectralType: 'M', colorIndex: 1.0 };
}
// A small fixture standing in for a slice of the star catalogue, used to exercise the
// exoplanet host-star cross-referencing logic without hitting any real API.
const FIXTURE_STARS: StarRecord[] = [
// The Sun sits at the origin, exactly where a host with a missing distance lands.
@@ -22,46 +27,107 @@ describe('normalizeStarName', () => {
describe('resolveHostStarId', () => {
it('matches by exact (normalized) host star name', () => {
const id = resolveHostStarId({ hostname: 'Proxima Centauri', raDeg: NaN, decDeg: NaN, distancePc: NaN }, FIXTURE_STARS, 0.5);
const id = resolveHostStarId({ hostname: 'Proxima Centauri', raDeg: NaN, decDeg: NaN, distancePc: NaN }, FIXTURE_STARS);
expect(id).toBe(1);
});
it('matches by name regardless of case/spacing differences', () => {
const id = resolveHostStarId({ hostname: 'gj3512', raDeg: NaN, decDeg: NaN, distancePc: NaN }, FIXTURE_STARS, 0.5);
const id = resolveHostStarId({ hostname: 'gj3512', raDeg: NaN, decDeg: NaN, distancePc: NaN }, FIXTURE_STARS);
expect(id).toBe(3);
});
it('falls back to nearest-neighbour position matching when the name is unknown', () => {
// Slightly off from Sirius's exact position, within tolerance.
const id = resolveHostStarId({ hostname: 'Sirius A', raDeg: 101.29, decDeg: -16.72, distancePc: 2.64 }, FIXTURE_STARS, 0.5);
expect(id).toBe(2);
});
it('returns null when no name match and no star is within tolerance', () => {
const id = resolveHostStarId({ hostname: 'Unknown Star XYZ', raDeg: 0, decDeg: 0, distancePc: 100 }, FIXTURE_STARS, 0.5);
expect(id).toBeNull();
});
it('returns null when there is no name match and no position is available', () => {
const id = resolveHostStarId({ hostname: 'Unknown Star XYZ', raDeg: NaN, decDeg: NaN, distancePc: NaN }, FIXTURE_STARS, 0.5);
const id = resolveHostStarId({ hostname: 'Unknown Star XYZ', raDeg: NaN, decDeg: NaN, distancePc: NaN }, FIXTURE_STARS);
expect(id).toBeNull();
});
it('picks the closest star when more than one falls within tolerance', () => {
const stars: StarRecord[] = [
{ id: 10, name: 'Near', x: 0, y: 0, z: 0, magnitude: 5, spectralType: 'G', colorIndex: 0.5 },
{ id: 11, name: 'Far', x: 0.4, y: 0, z: 0, magnitude: 5, spectralType: 'G', colorIndex: 0.5 }
];
const nameIndex = buildStarNameIndex(stars);
describe('matching on the sky', () => {
// GJ 887's archive row: position at Gaia's epoch, carried by 6.9″/yr of proper motion —
// 110″ from where the catalogue has the star at J2000. The matcher must carry the query
// back those sixteen years itself.
it('matches a host published at the Gaia epoch to its star at J2000', () => {
const lacaille9352 = star(70, 'Lacaille 9352', 346.46683, -35.85306, 3.29);
const archive = propagateProperMotion(346.46683, -35.85306, 6768.2, 1327.52, 16);
const id = resolveHostStarId({ hostname: 'Unmatched', raDeg: 0, decDeg: 0, distancePc: 0.2 }, stars, 0.5, nameIndex);
const id = resolveHostStarId(
{ hostname: 'GJ 887', raDeg: archive.raDeg, decDeg: archive.decDeg, distancePc: 3.28679, pmRaMasPerYear: 6768.2, pmDecMasPerYear: 1327.52 },
[lacaille9352]
);
expect(id).toBe(10);
expect(id).toBe(70);
});
// alf Tau's archive row publishes J2000 outright, and the archive never says which epoch a
// row is at. If the matcher trusted one epoch and carried every query back, Aldebaran's
// planet would land on the Gliese entry sitting 3″ from the carried-back point; the raw
// position, zero arcseconds from Aldebaran itself, has to win.
it('keeps a host published at J2000 on its star, proper motion or not', () => {
const aldebaran = star(80, 'Aldebaran', 68.980163, 16.509302, 20.43);
const carried = propagateProperMotion(68.980163, 16.509302, 63, -189, -16);
const ghost = star(81, 'Gl 171.1B', carried.raDeg, carried.decDeg + 3 / 3600, 20.43);
const id = resolveHostStarId(
{ hostname: 'alf Tau', raDeg: 68.980163, decDeg: 16.509302, distancePc: 20.43, pmRaMasPerYear: 63, pmDecMasPerYear: -189 },
[ghost, aldebaran]
);
expect(id).toBe(80);
});
// GJ 15 A's archive row sits at J2016, 46″ along its proper motion from Groombridge 34's
// J2000 place — and only 16″ from an unrelated Gaia entry. Nearest-to-the-published-point
// picks the interloper; carrying the query back the sixteen years must put the planets on
// the star that actually moved there.
it('picks the star the proper motion says the query is, not the entry nearest the published point', () => {
const primary = star(90, 'Groombridge 34', 4.595364, 44.022955, 3.562);
const published = propagateProperMotion(4.595364, 44.022955, 2891.5, 411.9, 16);
const interloper = star(91, 'Gaia DR3 385334196532776576', published.raDeg, published.decDeg + 16 / 3600, 3.563);
const id = resolveHostStarId(
{ hostname: 'GJ 15 A', raDeg: published.raDeg, decDeg: published.decDeg, distancePc: 3.56228, pmRaMasPerYear: 2891.5, pmDecMasPerYear: 411.9 },
[interloper, primary]
);
expect(id).toBe(90);
});
// GJ 273 is Luyten's Star to the arcsecond, but the archive publishes 5.92 pc for a star
// at 3.79 — a 56% disagreement. Direction alone must not override a distance in flat
// contradiction, or every line-of-sight coincidence becomes a match.
it('refuses a host whose distance flatly contradicts the star it points at', () => {
const luytens = star(100, "Luyten's Star", 111.8496, 5.2258, 3.79);
const id = resolveHostStarId({ hostname: 'GJ 273', raDeg: 111.8496, decDeg: 5.2258, distancePc: 5.921535 }, [luytens]);
expect(id).toBeNull();
});
// The tolerance is transverse — parsecs on the sky, not an angle — so the same 15″ offset
// is a match at 50 pc and a stranger at 200 pc.
it('scales the angular tolerance with the host distance', () => {
const at200 = resolveHostStarId(
{ hostname: 'Unmatched', raDeg: 150, decDeg: -40 + 15 / 3600, distancePc: 200 },
[star(110, 'Far', 150, -40, 200)]
);
const at50 = resolveHostStarId(
{ hostname: 'Unmatched', raDeg: 150, decDeg: -40 + 15 / 3600, distancePc: 50 },
[star(111, 'Near', 150, -40, 50)]
);
expect(at200).toBeNull();
expect(at50).toBe(111);
});
it('reuses a prebuilt name index when given one', () => {
const nameIndex = buildStarNameIndex(FIXTURE_STARS);
const id = resolveHostStarId({ hostname: 'Sirius', raDeg: NaN, decDeg: NaN, distancePc: NaN }, [], nameIndex);
expect(id).toBe(2);
});
});
describe('missing distance column', () => {
@@ -70,25 +136,25 @@ describe('resolveHostStarId', () => {
// the Sun at distance 0. That shipped 127 alien planets, all seven TRAPPIST-1 worlds among
// them, into our own solar system.
it('does not match a host with a zero distance to the Sun', () => {
const id = resolveHostStarId({ hostname: 'TRAPPIST-1', raDeg: 346.6, decDeg: -5.04, distancePc: 0 }, FIXTURE_STARS, 0.5);
const id = resolveHostStarId({ hostname: 'TRAPPIST-1', raDeg: 346.6, decDeg: -5.04, distancePc: 0 }, FIXTURE_STARS);
expect(id).toBeNull();
});
it('rejects a negative distance too', () => {
const id = resolveHostStarId({ hostname: 'Nowhere', raDeg: 10, decDeg: 10, distancePc: -3 }, FIXTURE_STARS, 0.5);
const id = resolveHostStarId({ hostname: 'Nowhere', raDeg: 10, decDeg: 10, distancePc: -3 }, FIXTURE_STARS);
expect(id).toBeNull();
});
it('still matches a real host at a genuinely small distance', () => {
const id = resolveHostStarId({ hostname: 'Unmatched', raDeg: 217.4, decDeg: -62.68, distancePc: 1.2959 }, FIXTURE_STARS, 0.5);
const id = resolveHostStarId({ hostname: 'Unmatched', raDeg: 217.4, decDeg: -62.68, distancePc: 1.2959 }, FIXTURE_STARS);
expect(id).toBe(1);
});
it('lets a named host resolve even with no usable distance', () => {
const id = resolveHostStarId({ hostname: 'Sirius', raDeg: 101.3, decDeg: -16.7, distancePc: 0 }, FIXTURE_STARS, 0.5);
const id = resolveHostStarId({ hostname: 'Sirius', raDeg: 101.3, decDeg: -16.7, distancePc: 0 }, FIXTURE_STARS);
expect(id).toBe(2);
});