Fill in the Sun's faint neighbours from Gaia, and fold the Gliese entries they repeat

Gaia's G < 12 cut took a quarter of what lies within 10 pc: the red,
brown and white dwarfs most of the neighbourhood is made of, which the
map only had where Gliese happened to list them. Teegarden's Star was
missing, and with it its three planets' host.

A second query fetches the complement out to 50 pc: G >= 12 or no G,
parallax > 20 mas, with pmra/pmdec so the J2016 -> J2000 propagation
applies. The quality filter was chosen by counting. Parallax over error
> 5 keeps 39 751 of the 39 764 sources that pass the floor, but the Gaia
Catalogue of Nearby Stars (GCNS; Gaia Collaboration, Smart et al. 2021)
rejects 11 752 of them as spurious: median G 20.2, astrometric excess
noise 5.4 mas against 0.15 for the ones it keeps, 6 933 toward the
Galactic centre. So the query joins the GCNS main table (EDR3 astrometry
and source ids, which DR3 carries unchanged) and keeps 28 012 rows; the
error cut stays and costs no GCNS source, brown dwarfs included. The
query has its own row-count floor (28 012) and the row-limit cap, and is
ordered by (phot_g_mean_mag, source_id); a second ETL run reproduced
stars.bin, stars-meta.bin and stars-index.json byte for byte. Its ids
start at 1 050 000 000, clear of the main query's and under 2^30, which
V8 keeps unboxed: numbered from 2 000 000 000 they made the app's boot
task 230 ms longer (medians of five interleaved runs, 1.41 s against
1.18). validateStars now refuses an id outside 0 to 2^30.

The Gliese entries these stars duplicate were not folded: HYG carries
them with positions off by up to a minute of arc and photometric
distances, so they missed the 15" tolerance or failed the distance test.
Their proper motions, which Gliese measured well, give them away:
isSameStar now takes two entries moving within 20 % of each other as one
star up to 60" apart, whatever their distances, brightness still
permitting. Of the 602 Gliese-only rows left without a counterpart, 253
have such a Gaia entry; with every entry shifted a quarter degree, none
does. fetchStars passes HYG's motions only for rows without Hipparcos
astrometry: given them too, 15 Hipparcos stars took a co-moving
companion's Gaia entry and the cross-catalogue pairs under an arcsecond
went from 23 to 35. Of HYG's 1 200 stars fainter than V 12 within 25 pc,
1 024 now sit on a Gaia position (325 before); of the 176 left alone, 43
still have a Gaia entry 3-60" away (218 without the motion rule), some of
them real companions.

Measured on the rebuilt catalogue, against the GCNS (sources with
parallax > 100, 40 and 20 mas):
  within 10 pc  336 -> 372  (GCNS 312; the map adds 60 HYG-only stars)
  within 25 pc  3 652 -> 5 560  (GCNS 5 111)
  within 50 pc  13 702 -> 40 916  (GCNS 40 231)
452 331 stars (+27 214). Proxima, Barnard's Star, Wolf 359, Rigel, Deneb
and Alnilam are all present by name; Teegarden's Star is Gaia DR3
35227046884571776 at 3.83 pc and hosts its three planets. Luhman 16 is
not in Gaia DR3 with a parallax (5353626573555863424 has a two-parameter
solution) and stays absent. 94 more exoplanets find a host (2 071), none
changes host. TRAPPIST-1 is now drawn (Gaia DR3 2635476908753563008,
12.47 pc) but its planets are not yet matched to it.

Merge gate, ceilings unchanged: HYG rows without a Gaia counterpart
12 352 -> 11 554 (ceiling 15 000; 10 886 before the naked-eye stars),
cross-catalogue pairs under an arcsecond 23 -> 23 (ceiling 100). The
gate's comment now accounts for the survivors by magnitude.

gzip -9 sizes against the catalogue before both changes: stars.bin
4 711 922 -> 5 030 741 B, stars-meta.bin 2 576 213 -> 2 784 614 B,
stars-index.json 3 724 855 -> 4 003 584 B (+806 KB, 7.3 %). Boot on the
dev server, five interleaved cold runs: the task that indexes the
catalogue after the data lands, median 1 072 -> 1 182 ms; HUD shown,
median 2 622 -> 2 716 ms. This machine measured 0.82-1.30 s for the
same baseline task today, above audit #25's 627-843 ms. The drawn-star
budget is unchanged.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

tools/etl/build.ts

@@ -26,6 +26,9 @@ function validateStars(stars: StarRecord[]): void {
   const ids = new Set<number>();
   for (const star of stars) {
     assertCondition(Number.isFinite(star.id), `Star has a non-numeric id: ${JSON.stringify(star)}`);
+    // Under 2^30, which V8 keeps unboxed; past it every id is a heap number, and the app's boot
+    // task grew by 230 ms when the nearby Gaia stars were numbered from 2 000 000 000.
+    assertCondition(star.id >= 0 && star.id < 2 ** 30, `Star ${star.id} has an id outside 0 to 2^30.`);
     assertCondition(!ids.has(star.id), `Duplicate star id: ${star.id}`);
     ids.add(star.id);
     assertCondition(!!star.name, `Star ${star.id} has no name.`);
@@ -59,26 +62,28 @@ function validateStars(stars: StarRecord[]): void {
  *
  * A star kept twice leaves its two entries near each other on the sky, from *different* sources —
  * one catalogue does not list a star twice. Under an arcsecond that is never two stars at this
- * depth, so every such pair is a miss. Nineteen survive today, all of them a second HYG row
- * wanting a Gaia entry that already absorbed one (Gliese lists some doubles twice); the merge
- * that trusted a Hipparcos parallax over direction left 1 112.
+ * depth, so every such pair is a miss. Twenty-three survive today; the nineteen first counted were
+ * all a second HYG row wanting a Gaia entry that already absorbed one (Gliese lists some doubles
+ * twice), and the merge that trusted a Hipparcos parallax over direction left 1 112.
  *
  * The other failure leaves no close pair at all, because proper motion had already carried the
  * two entries tens of arcseconds apart — the 2026-08-24 refresh, where HYG sat at epoch 2000.0
  * and Gaia at J2016.0. What it does leave is HYG rows that found no counterpart: 36 056 of them
- * against the 12 352 today, and no counterpart was possible for most of those. 8 301 of them are
+ * against the 11 554 today, and no counterpart was possible for most of those. 8 301 of them are
  * every star in the published catalogue beyond 250 pc, which the main query never downloads: 6 835
  * that Gaia's parallax puts past `ETL_GAIA_DISTANCE_PC` while Hipparcos put them inside
- * `ETL_STAR_DISTANCE_PC`, and 1 466 naked-eye stars kept at any distance. The rest are what Gaia
- * genuinely lacks: bright stars it saturates on, red dwarfs past its magnitude cut. So the headroom
- * left to the ceiling tracks the gap between those two cutoffs as much as Gaia's completeness.
+ * `ETL_STAR_DISTANCE_PC`, and 1 466 naked-eye stars kept at any distance. The other 3 252 are what
+ * Gaia genuinely lacks: 1 194 brighter than V 8, which it saturates on or measures poorly, 1 832
+ * between 8 and 12, and 226 fainter, 184 of them Gliese stars within 50 pc that neither of its
+ * queries holds. So the headroom left to the ceiling tracks the gap between those two cutoffs as
+ * much as Gaia's completeness.
  *
  * This bounds a merge that went wrong, and — loosely — a Gaia download that came back short: a
  * truncated answer leaves the HYG rows whose counterpart it dropped without one, so survivors go
- * *up*, not down. Measured before the naked-eye stars joined, which add about 1 466 to each
- * figure: 10 886, 11 004 at nine tenths of the rows, 12 711 at half, 16 258 at a third. So this
- * ceiling only catches a deep truncation, and `fetchGaiaStars` catches the shallower ones with its
- * own row floor.
+ * *up*, not down. Measured on the main query when it was the only one, with 10 886 survivors
+ * against today's 11 554: 11 004 at nine tenths of its rows, 12 711 at half, 16 258 at a third. So
+ * this ceiling only catches a deep truncation, and `fetchGaiaStars` catches the shallower ones
+ * with a row floor on each query.
  */
 const MAX_UNMERGED_TWINS = 100;
 const MAX_HYG_SURVIVORS = 15_000;