skymap
Fly from Earth's surface to the edge of the observable universe in one true-scale WebGPU scene, built from real survey data.
Live demo → · Chrome 113+ · Edge 113+ · Firefox 141+ (145+ on Apple Silicon macOS) · Safari 26+
The zoom
Skymap covers nineteen orders of magnitude, from Earth's surface (about 10⁷ m) to the horizon of the observable universe (about 10²⁶ m), in a single scene with no scale breaks. Zoom out from Earth and you pass the planets, then the Gaia star field, then the galactic disk, and finally the cosmic web: about three million catalogued galaxies. Everything sits where its catalog says it should.
The guided tour, "The Long Way Out," plays the whole descent with captions and timed camera moves. You can also just explore: orbit freely, or jump anywhere by name with Cmd+K. Skymap is meant for teaching large-scale structure, for outreach, and for browsing the catalogs themselves.
The framing owes everything to Powers of Ten (Charles and Ray Eames, 1977); skymap tries the same journey with today's measured universe, and hands you the camera.
Highlights
- Galaxies: about 3 million from SDSS, 2MRS, GLADE, and Milliquas. Each is a dot until you approach, then a procedural disk, then a real thumbnail (how).
- Cosmic web: a DisPerSE filament skeleton and an MCPM slime-mould density volume trace the structure between the points.
- Structures: clusters, superclusters, voids, and groups from MCXC, MSCC, and other VizieR catalogs, with markers and labels.
- Famous galaxies: curated thumbnails and descriptions for the well-known Messier and NGC objects.
- Stars: 16.8 million from Gaia DR3, extended by the GCNS and Hipparcos-2 supplements. Stars close enough to resolve become true-scale spheres.
- Galactic centre: the S-stars orbit Sagittarius A* on their measured Keplerian elements, with trails.
- Solar system: runs on a live clock. All the planets plus Pluto and Charon, Saturn's rings, orbit trails, the Sun with bloom.
- Earth: PBR shading, night lights, relief, clouds, an atmosphere, and streamed surface tiles down to city scale.
- Time: jump the simulation to any date, change its rate, and share the moment with a
#t= link.
- Search: Cmd+K reaches the famous atlas, 48,000 PGC name aliases, and named structures.
#focus= links share camera targets; #exhibit=, #tour=, and #clip= links open a curated view or set it playing.
- Opt-in: DESI DR1 cones, the CF4++ flow field, constellations, and the CF-4 dark-matter volume are off by default in the Settings panel.
- Debug: press
d for per-pass GPU timings and render-pass toggles.
- Reproduce a view: press
l (the link prints to the console) or click copy URL in the debug panel's Camera section for a #pose= link that reopens the exact camera at the exact moment. Paste it into a bug report and the reader sees what you saw.
Gallery
Earth from low orbit, with night lights and streamed surface tiles over the base map.
The solar system at the current simulated time.
The Gaia star field giving way to the procedural Milky Way disk.
The local volume: famous galaxies with curated thumbnails, structure labels, and filaments.
The point cloud, filament skeleton, and MCPM volume at supercluster scale.
The data
Every dataset skymap renders is listed below. docs/science.md explains how catalogue brightness, colour, and selection effects turn into pixels. Full citations and license terms live in ATTRIBUTIONS.md.
Sky
| Source | Contributes |
|---|
| SDSS DR17 (spectroscopic) | Deep northern spectroscopic slice, ~500k galaxies |
| 2MRS | All-sky near-IR redshift survey, local volume in every direction |
| GLADE v2.3 | All-sky million-galaxy compilation, fills SDSS's footprint gaps |
| Milliquas v8 | ~940k spectroscopic quasars and AGN |
| DESI DR1 LSS | Deep cone (Corona Borealis), wedge, and Sloan Great Wall slices; off by default |
| Gaia DR3 + GCNS + Hipparcos-2 | ~16.8M Milky Way stars, local 100 pc supplement, naked-eye bright stars |
| Famous atlas | Curated Messier/NGC thumbnails and editorial descriptions |
| MCXC + MSCC + VizieR structures | Cluster, supercluster, void, and group markers |
| DisPerSE filaments | Derived cosmic-web skeleton, computed offline from the point cloud |
| CF-4 density (Courtois 2025) |
Solar system
Quickstart
Requires Node 24+ (nvm use picks it up from .nvmrc).
npm install
npm run dev
Open http://localhost:5173. Drag to orbit, scroll to zoom (on touch: drag and pinch).
For real data, pull the prebuilt catalogs:
npm run fetch-data
This downloads the catalog, star, structure, and filament binaries from R2 into public/data/. They are the same files the live site serves. If you want to build them from the raw catalogs instead, see docs/DATA.md.
How it works
The render loop lives in a long-running imperative engine. React subscribes to it for the handful of state slices the UI needs and owns nothing that updates per frame. The engine renders on demand: input and loading events request a frame, and the loop goes idle when nothing is moving. Every visible pass draws into one rgba16float HDR target, tone-mapped to the display at the end of the frame. Reversed-Z depth and a floating-origin camera hold precision across the full 10⁷–10²⁶ m range.
Catalog data ships in binary formats, tiered, content-hashed, and streamed from R2 through a manifest fetched at boot:
- SKMP v9: galaxies, 64 bytes per row
- SKOI / SKOC v1: stars as an octree index plus chunk objects (SKST v1 tier bins remain as the alternative
format: 'skst')
- CCAT v1: structures (clusters, superclusters, voids, groups)
- SCFD v3: scalar fields (density and flow volumes)
- FILA v1: filaments
For more depth: docs/RENDERER.md (renderer map, WebGPU landmines), docs/DATA.md (pipeline, binary formats), docs/science.md (rendering conventions), docs/adrs/ (decision records).
Finding your way around
The code is documented didactically throughout. If you're also looking to learn WebGPU, GPU picking, or the basics of cosmological coordinate math, the source is meant to be read.
src/
components/ React UI shell (settings, info cards, tour, time bar)
services/
engine/ frame program, render scheduling, catalog loading
gpu/ renderers and the WGSL/WESL shaders
camera/ orbit camera, tweens, animation clips
state/ Redux Toolkit slices, selectors, sagas
data/ source registry and binary format specs
utils/ pure helpers, heavily tested
tools/ data pipeline: fetchers, builders, workbenches, recorder
data/raw/ raw catalog downloads (payloads gitignored)
public/data/ built binaries the renderer loads (gitignored)
docs/ DATA.md, RENDERER.md, science.md, adrs/, BACKLOG.md
tests/ Vitest suite, mirrors src/
Dev tools
- Three renderer workbenches deploy next to the main app: /galaxy/ (procedural Hubble-sequence galaxy), /mcpm/ (MCPM cosmic-web workbench), /flow/ (CF4++ flow-field visualizer)
npm run perf measures per-pass GPU timings headlesslynpm run record-tour renders the guided tour to 4K video offline- The Vitest suite runs 7,500+ tests across 1,100+ files, mirroring the
src/ tree
Direction
- More measured data where procedural stand-ins currently fill in
- Work further down the powers-of-ten scale, from Earth's surface toward human scale
- Spatial chunking to get past the few-million-point ceiling; SDSS's full photometric catalog holds around a billion objects
- Wider platform support as WebGPU lands in more browsers
The live queue is docs/BACKLOG.md.
Cite, credit, and license
If you use skymap in a publication, talk, or derived work, please cite it via CITATION.cff. GitHub's "Cite this repository" sidebar button exposes BibTeX and APA forms.
Skymap's source code is MIT-licensed; see LICENSE. The catalog data, imagery, and external services it uses carry their own citation requirements and license terms: some are public domain or CC BY, some are non-commercial (Gaia's stars are CC BY-NC, the close-up Earth imagery CC BY-NC-SA), and several state no licence at all. So the MIT licence does not cover what skymap shows, or pictures taken of it. Each source is listed with its terms in ATTRIBUTIONS.md.
To work on skymap, start with CONTRIBUTING.md.
CLAUDE.md at the repo root is onboarding guidance for AI coding assistants. It isn't load-bearing for the build or runtime. It exists because parts of this project were developed with AI assistance, and that context helps future AI-assisted edits.
