Draw every star at its own radius, measured where the archive has one and derived otherwise

The system view drew the Sun at its own radius and every other star at 0.45 of its innermost
orbit, capped at 0.2 AU: a size chosen so the star would not swallow its planets, not the star's.
Proxima Centauri was drawn at 2.8 solar radii, eighteen times its own, and every star without
planets at 43.

starSurfaceOf (body-view-model.ts) now gives each star a radius and a temperature. A planet host
takes the archive's st_rad and st_teff from its planets' rows: 4 439 hosts are drawn at a
measured radius, 22 at a derived one. Every other star's is derived: its temperature off Pecaut & Mamajek's dwarf
sequence at its colour (the same table the spectral estimate reads, or at the colour its type
implies where it has none), its luminosity from its absolute magnitude and the bolometric
correction luminositySolar already applies, and R = sqrt(L) / (T / 5772 K)^2. Against the
archive's own st_rad for the 1 447 catalogue hosts that have one, the derived radius is within
0.018 dex at the median, 0.071 dex at the 90th percentile, and within a factor of 1.5 for
97.1 %. Sirius comes out 1.79 solar radii (1.711 published, Liebert et al. 2005), Wolf 359 0.117,
Betelgeuse 584, the Sun exactly 1.

A star with no band has only the ETL's stand-in magnitude, and gets no derived radius: PSR
J1719-1438 came out 2.3 solar radii from it, wider than its planet's orbit. With the stars that
have neither a colour nor a type, that leaves 3 077 of 455 608 stars (274 of 4 735 hosts) with
no radius; they are drawn at the Sun's, and their card gives none.

The card says which it is: "Radius 0.141 solar radii" for a published one, "~0.10 solar radii,
from colour and brightness" for a derived one, two figures because colour does not give three.

A giant drawn at its size can be wider than its system, so systemFramingDistanceAu also makes
room for the star, and the controls' closest approach is now three of the star's radii where
that is more than the old 0.05 AU. 23 211 stars are drawn wider than 3.6 solar radii, which put
0.05 AU inside three of their radii, and a zoom would have carried the camera through the
surface of the largest. The Sun keeps 0.05 AU. starMarkerRadiusAu and the renderer's innermost
axis, which only it read, are gone.

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

src/app/shared/astro/stellar.spec.ts

@@ -1,6 +1,15 @@
 import { describe, expect, it } from 'vitest';
 
-import { absoluteMagnitude, bolometricCorrection, luminositySolar, SOLAR_ABSOLUTE_MAGNITUDE_V, SOLAR_BOLOMETRIC_MAGNITUDE } from './stellar';
+import {
+  absoluteMagnitude,
+  bolometricCorrection,
+  effectiveTemperatureK,
+  luminositySolar,
+  radiusFromLuminositySolar,
+  SOLAR_ABSOLUTE_MAGNITUDE_V,
+  SOLAR_BOLOMETRIC_MAGNITUDE,
+  SOLAR_EFFECTIVE_TEMPERATURE_K
+} from './stellar';
 
 /** Real catalogue rows, with the published luminosity each one should reproduce. */
 const SIRIUS = { magnitude: -1.44, distancePc: 2.6371, spectralType: 'A0m...', publishedLuminosity: 25.4 };
@@ -122,3 +131,36 @@ describe('luminositySolar', () => {
     expect(luminositySolar({ magnitude: 5, distancePc: -1 })).toBeNull();
   });
 });
+
+describe('effectiveTemperatureK', () => {
+  it("is the Sun's own for the Sun", () => {
+    expect(effectiveTemperatureK({ magnitude: -26.7, distancePc: 0, colorIndex: 0.7 })).toBe(SOLAR_EFFECTIVE_TEMPERATURE_K);
+  });
+
+  it('reads a colour in its own system, and a spectral type where there is no colour', () => {
+    // An M5 dwarf is 3 060 K at B−V 1.83 or BP−RP 3.35. Its type alone goes through the colour
+    // `spectralTypeToColorIndex` gives it, B−V 1.70, and comes out a little warmer.
+    expect(effectiveTemperatureK({ magnitude: 11, distancePc: 5, colorIndex: 3.35, colorSystem: 'BP-RP' })).toBeCloseTo(3060, 0);
+    expect(effectiveTemperatureK({ magnitude: 11, distancePc: 5, colorIndex: 1.83, colorSystem: 'B-V' })).toBeCloseTo(3060, 0);
+    expect(effectiveTemperatureK({ magnitude: 11, distancePc: 5, spectralType: 'M5Ve', colorIndex: null })).toBeCloseTo(3106, 0);
+    expect(effectiveTemperatureK({ magnitude: 11, distancePc: 5, spectralType: 'Unknown', colorIndex: null })).toBeNull();
+  });
+});
+
+describe('radiusFromLuminositySolar', () => {
+  it('is one for the Sun', () => {
+    expect(radiusFromLuminositySolar(1, SOLAR_EFFECTIVE_TEMPERATURE_K)).toBeCloseTo(1, 12);
+  });
+
+  it('gives Sirius and TRAPPIST-1 their published radii from colour and brightness alone', () => {
+    // 1.711 R☉ (Liebert et al. 2005) and 0.119 R☉ (Agol et al. 2021), each to within a fifth.
+    for (const [star, published] of [
+      [{ magnitude: -1.44, distancePc: 2.6371, magnitudeBand: 'V', colorIndex: 0.009, colorSystem: 'B-V' }, 1.711],
+      [{ magnitude: 15.6226, distancePc: 12.467, magnitudeBand: 'G', colorIndex: 4.902, colorSystem: 'BP-RP' }, 0.119]
+    ] as const) {
+      const radius = radiusFromLuminositySolar(luminositySolar(star)!, effectiveTemperatureK(star)!);
+      expect(radius / published).toBeGreaterThan(0.8);
+      expect(radius / published).toBeLessThan(1.2);
+    }
+  });
+});