Derive a surface for every body that was never photographed

Fifteen bodies here have a real photograph. Every exoplanet does not, and
never will on current instruments — none has ever been imaged — and nor do
several of the solar system's own moons. Those all shared one crude
stand-in: a few noisy bands tinted by category, cached per colour, so
every exoplanet in the app was literally the same picture.

They now get a surface reasoned from what has actually been measured.

The chain is standard at every link. A host star's luminosity comes from
its catalogued apparent magnitude and its parallax distance — that pair is
exactly an absolute magnitude — plus a bolometric correction for its
spectral class. The correction is not optional: an M dwarf radiates most
of its light in the infrared, so its visual magnitude understates it more
than tenfold, and M dwarfs are what most nearby planet hosts are.
Luminosity and the semi-major axis then give an equilibrium temperature,
mass and radius give a bulk density, and size, temperature and density
together give a class of world.

Checked against the solar system the temperatures land on Earth 255 K,
Jupiter 112 K, Neptune 46 K, all within a kelvin or two of published
values, and 51 Pegasi b comes out at 1227 K against a published 1200.

Each class carries a palette reasoned from its chemistry — methane absorbs
red light, which is why the ice giants are blue — and a structure: zonal
bands for a body with a fluid envelope, because a rapidly rotating
atmosphere organises into them, and fractal terrain for one with a solid
surface. Polar caps grow and shrink with the derived temperature, which is
the clearest visible consequence of the whole chain.

The generator samples three-dimensional noise along the sphere rather than
a flat field, so there is no seam to stitch at the antimeridian and no
pinching at the poles, and it writes into a byte array rather than a
canvas — a pure function, testable, with no 2D context to be unavailable.

Two things the derivation cannot do, both stated on screen next to the
measurements it rests on. Equilibrium temperature ignores greenhouse
warming and internal heat, so Venus comes out at 300 K against a real
surface of 737 K and Io, kept molten by tides, classifies as ice. And
these are illustrations: reasoned, but not observations.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WaySiNst4HhDXBHnMy8p5G

.junie/plans/nasa-star-map.md

@@ -135,6 +135,8 @@ interface DeepSkyRecord {
 - `SystemOrbitsRenderer` — draws orbit ellipses and planet/exoplanet markers for the currently focused star system, using the Kepler propagator.
 - `KeplerPropagator` (`shared/astro/kepler.ts`) — pure function(s) converting `OrbitalElements` + epoch → Cartesian position; independently unit-testable.
 - `BodyDetailSceneComponent` — separate route/component with its own dedicated scene for a close-up view of one selected body, plus an `InfoPanelComponent` showing its data.
+- `planet-appearance.ts` / `stellar.ts` (`shared/astro/`) — derives a host star's luminosity from its catalogued magnitude and distance, a planet's equilibrium temperature and bulk density from that, and a class of world from those.
+- `procedural-planet-texture.ts` (`shared/rendering/`) — paints an equirectangular surface from that derivation: zonal bands for a fluid envelope, fractal terrain for a solid one, polar caps sized by temperature. A pure function over a byte array, no canvas.
 - `SearchComponent` — text search across `stars-index.json`, `bodies.json`, `exoplanets.json`; on match, dispatches a navigation action.
 - `NavigationStore` (Angular signals-based) — holds `viewLevel: 'galactic' | 'galaxy' | 'system'`, `selectedStarId`, `selectedBodyId`; consumed by scene components and routed body-detail view.
 - `MilkyWayRenderer` / `milky-way-model.ts` — the Galaxy itself as an instanced particle cloud scattered around the structural model in `shared/astro/galaxy.ts`, crossfaded against the catalogued star field by camera distance.
@@ -297,3 +299,10 @@ The same plane-and-tether reading aid the outer scales got, applied to a single
 - Add `systemGridRingsAu`: ring radii snapped to a 1-2-5 ladder so a distance can be read off, at any of the four orders of magnitude real systems span.
 - Draw the grid and the body tethers in the system's own reference plane — the ecliptic for the solar system, the plane of the sky otherwise — dashed, so it is never mistaken for an orbit.
 - Frame the camera against that same plane, so an exoplanet system is presented face-on rather than edge-on.
+
+### ✓ Step 9: Give every body a surface
+Real photography where it exists, and a surface reasoned from measurements where it does not.
+- Derive host-star luminosity from apparent magnitude, parallax distance and a bolometric correction; validate against published values for real stars.
+- Derive equilibrium temperature and bulk density from it, and classify each world by size, temperature and density; validate against the solar system's own bodies.
+- Paint the surface procedurally from that class, seeded per body so it is stable between visits, and apply it in both the body-detail view and the system-view markers.
+- State the derivation and its limits on screen, next to the measurements it rests on.