Astraeus DemosAssetsGitHub
An open-source engine for space stories · TypeScript · Three.js

Everything in space, where it is right now.

Astraeus does the hard part of space on the web: time, orbits, reference frames and astronomical scale. Every body answers one question, where are you at this moment, and every answer says where it came from. You bring the story.

Read the code See it running
the one questionMIT
// Where was the Moon when Eagle landed?
moon.stateAt(Date.parse("1969-07-20T20:17:40Z"), "earth")

{
  frame:      "EQJ",      // J2000 equatorial
  center:     "earth",
  positionKm: [-385_000, -48_000, -31_000],
  provenance: {
    sourceType: "ephemeris",
    sources:    ["orb.js lunar series"],
  }
}
// JPL Horizons, same instant: −385,275 · −47,906 · −30,879 km

Four layers, one door in.

A planet, a spacecraft, a comet and twenty-five thousand meteoroids all enter the same way. Everything downstream draws them the same way.

  1. 01 · STATE

    Where and when

    Time scales, positions, velocities, orientation and frames, each with its source and accuracy.

    UTC·TT·TDBJ2000provenance
  2. 02 · SOURCES

    Plug in the data

    Planet theory, NASA mission samples, published orbits, measured meteor catalogues. Swap one without touching the rest.

    VSOP87Keplercatalogues
  3. 03 · DRAWING

    Safe at any scale

    True or readable scale, a floating origin so 51 AU stays steady, paths, labels, light and a real star sky.

    floating originmarkerssky
  4. 04 · STORY

    Time you can play

    Timelines, events, focus and follow, story panels that open as playback reaches their moment, and an info panel that shows what's measured and what's filled in.

    observedmodelledillustrative

The shelf, ready to use.

Bodies, sky and data that ship with the engine's demos, each with its source and licence on record.

SunCC BY 4.0
MercuryCC BY 4.0
VenusCC BY 4.0
EarthNASA Earth Observatory
MoonNASA SVS
MarsCC BY 4.0
JupiterCC BY 4.0
Iopublic domain
The ESO Milky Way panorama
SKYReal stars and the Milky Way

8,920 naked-eye stars from the HYG catalogue, and ESO's panorama in the same frame.
MEASURED ORBITSGlobal Meteor Network

Perseids from 2025, every meteor on its own ellipse. CC BY 4.0.

25,588
ORBITS AND MISSIONSNASA JPL and Apollo 11

A comet out to 51 AU, an asteroid from a settings file, and 30 timed Apollo events.

30

Every asset, the science behind it, and the credits →

Built with it.

Two stories that couldn't be more different, on the same engine with no special cases. Open Developer mode in either to see what's underneath, or to copy a link to the exact view on screen.

Apollo 11's path from Earth to the Moon and back, seen from above at true scale, with the touchdown story panel open: an Observed badge, two short paragraphs and the NASA mission report as its source.
July 1969

Apollo 11

Eight days to the Moon and back, rebuilt from NASA's mission report. Seven story panels open as the clock reaches each step, from leaving Earth orbit to splashdown, each with its sources.

mission dataevents7 story panels
Open
The Perseid meteor stream seen obliquely from above the planets' plane, a ribbon along comet Swift-Tuttle's orbit, every dot one measured orbit with its place along that orbit filled in, over the real star sky.
August 2027

The Perseids

Earth through comet Swift–Tuttle's trail. A whole shower from one settings file. Three story panels say what is measured here and what is filled in.

25,588 orbitssettings3 story panels
Open
  • 1question every body answers: where are you, now?
  • 25,588measured meteor orbits, drawn one by one
  • 51AUout to a comet's far end, without losing precision
  • 1settings file was all a new shower needed