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Give an archive star's distance error as the error on the distance it is, not as a parallax range

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formatDistance printed any error of a fifth or more as the range a parallax's error makes,
d/(1+e) to d/(1−e). A star the ETL places from the Exoplanet Archive carries the mean of sy_disterr1
and 2 instead, which the archive defines as one-sided errors on sy_dist in parsecs, and many of
those distances come from a lensing model with no parallax behind them. 129 of the 3 195 archive
stars with an error were printed as ranges the archive does not give: KMT-2016-BLG-1836L as 5.8 to
9.2 kpc, where the archive publishes 7 100 +800 −2 400 pc, and AT2021ueyL as 664 pc to 2.4 kpc
against 1 040 +740 −440.

The card now tells formatDistance when the error is on the distance (source exoplanet-archive), and
it keeps the ± at any size. Measured on the shipped catalogue: KMT-2016-BLG-1836L reads 7.1 ± 1.6 kpc,
AT2021ueyL 1.0 ± 0.6 kpc, EPIC 201170410 134 ± 43 pc, KMT-2016-BLG-0212L 6.3 ± 1.3 kpc. The ETL keeps
only the mean, so a lopsided interval such as KMT-2016-BLG-1836L's is shown symmetric; carrying both
errors would take a second column in stars-meta.bin. The doc comments on formatDistance and on
distanceError no longer say an archive distance is an inverted parallax.

Controls, each failing its named test: the error on the distance read as a parallax's (2 of 790
failed), and the card not saying it is on the distance (1 of 790).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Senrokai
2026-09-29 20:27:01 +02:00
co-authored by Claude Opus 5.5
parent d1aa22ed61
commit fa52f6a818
5 changed files with 30 additions and 8 deletions
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src/app/features/galaxy-system/star-readouts.spec.ts
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@@ -60,6 +60,13 @@ describe('starReadouts', () => {
expect(value(starReadouts(GAIA_STAR), 'Distance')).toBe('117 ± 12 pc');
});
it("gives an archive star's distance error as the archive does, on the distance, not as a parallax range", () => {
// KMT-2016-BLG-1836L, 7 100 +800 −2 400 pc: a mean of 22.5 %.
const lens = { ...GAIA_STAR, x: 7100, magnitudeBand: undefined, colorIndex: null, colorSystem: undefined, distanceError: 0.2254, distanceFromGaia: false, source: 'exoplanet-archive' };
expect(value(starReadouts(lens), 'Distance')).toBe('7.1 ± 1.6 kpc');
expect(value(starReadouts({ ...lens, source: 'hyg' }), 'Distance')).toBe('5.8 kpc to 9.2 kpc');
});
it('names the catalogue a star comes from, and whose distance it has', () => {
expect(value(starReadouts(GAIA_STAR), 'Source')).toBe('Gaia DR3');
expect(value(starReadouts(HYG_STAR), 'Source')).toBe('HYG');