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Carry the archive's positions back from Gaia DR2's J2015.5, where it publishes them, not J2016

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fetchExoplanets placed each star it adds from the Exoplanet Archive by carrying the archive's
position back sixteen years, and 4c8e4a0 said the archive publishes at Gaia's J2016. It does not:
its positions are Gaia DR2's at J2015.5 although it names the DR3 source. Barnard's star in the
archive, 269.4486144, 4.7379808, equals DR2 4472832130942575872 at J2015.5 to 1e-7°, and sits 5.2″
from DR3's J2016 place; the review found 66 of the 67 archive-placed stars moving over 100 mas a
year within 0.21 mas of their DR2 position and none within 1 mas of DR3's. The matcher's comment
made the same claim of HD 133131 and TOI-2459, whose positions are DR2's too.

host-star-matching.ts now exports CATALOGUE_EPOCH and ARCHIVE_EPOCH = 2015.5, the matcher carries a
query back by their difference, and fetchExoplanets uses the same two, so the epoch is written
once. From cache: only the 3 277 archive-placed stars move, 2 287 of them by more than a
milliarcsecond, 74 by more than 50 and TOI-2406 most, by 203 mas, half a year of its 405 mas/yr;
no planet changes host. Invisible at map scale; the point is that the constant and its comments
now say what the archive does.

Control: ARCHIVE_EPOCH back to 2016.0 fails "carries Barnard's star from the archive's position to
where Gaia DR3's goes, to a few milliarcseconds" (1 of 802), which puts the two 5.2″ apart. The
GJ 15 A matching fixture is now built at J2015.5 too. fetchExoplanets' use of the constant has no
test of its own; the ETL has no test harness.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
This commit is contained in:
Senrokai
2026-09-29 21:20:26 +02:00
co-authored by Claude Opus 5.5
parent 62f81f2c43
commit 6d81c45f45
4 changed files with 33 additions and 20 deletions
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tools/etl/fetchExoplanets.ts
+6 -6
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@@ -2,7 +2,7 @@ import { createHash } from 'node:crypto';
import { writeFileSync } from 'node:fs';
import { propagateProperMotion, raDegDecDistanceToXyz } from '../../src/app/shared/astro/coordinates';
import { archiveStarId, buildStarNameIndex, resolveHostStarId } from '../../src/app/shared/astro/host-star-matching';
import { ARCHIVE_EPOCH, archiveStarId, buildStarNameIndex, CATALOGUE_EPOCH, resolveHostStarId } from '../../src/app/shared/astro/host-star-matching';
import { temperatureToColorIndex } from '../../src/app/shared/astro/spectral';
import { ExoplanetRecord } from '../../src/app/shared/models/exoplanet.model';
import { isDesignation } from '../../src/app/shared/models/star-catalog';
@@ -87,12 +87,12 @@ const DISTANCE_ERRORS_CACHE_FILE = `exoplanet-archive-disterr-${createHash('sha1
const ARCHIVE_SOURCE = 'exoplanet-archive';
/**
* The archive's positions are at Gaia's epoch, J2016, not the catalogue's J2000: of the 746
* matched hosts moving over 100 mas a year, 741 sit nearer their star once carried back sixteen
* years (a median 0.11″ from it, against 3.47″ as published). The matcher tries both epochs; a
* star placed from the archive has to pick one.
* The archive's positions are at Gaia DR2's epoch, J2015.5, not the catalogue's J2000 (see
* `ARCHIVE_EPOCH`): of the 746 matched hosts moving over 100 mas a year, 741 sit nearer their star
* once carried back (a median 0.11″ from it, against 3.47″ as published). The matcher tries both
* epochs; a star placed from the archive has to pick one.
*/
const ARCHIVE_TO_CATALOGUE_YEARS = 2000 - 2016;
const ARCHIVE_TO_CATALOGUE_YEARS = CATALOGUE_EPOCH - ARCHIVE_EPOCH;
/** As in `fetchStars`: faint, for a host the archive gives neither a V nor a G magnitude. */
const UNKNOWN_MAGNITUDE = 15;