Enter the Observatory

Gathering light

The Sun, a white star with eight-pointed rays, at the centre of thin engraved orbits. The asteroid belt circles it as a haze of dust; the planets are small discs along their orbits, Saturn’s rings visible near the top.

Vast Universe

Light leaves the Sun. Follow it.

Enter the Observatory See it to scale

Scroll to travel with the light

The Sun fills the right of the frame: a golden disc, white-hot at its centre and deepening to orange at its rim, with a finely mottled surface, faint red prominences at its edge and a soft glow around it.

The Star

7 s of sunlight

The journey starts at the surface of a star 695,700 kilometres in radius.

Venus as a crescent against black space, lit from the left, where the Sun’s glare spreads long rays across the frame.

Inner worlds

6 min 3 s of sunlight

Mercury turns so slowly that one sunrise to the next takes 176 Earth days. Venus, next out, hides under clouds at 464 °C.

Earth eclipsing the Sun: its night side, a black disc scattered with city lights, ringed by the Sun’s pale corona.

Earth and Moon

8 min 20 s of sunlight

Sunlight takes a little over eight minutes to reach us. The glow on the night side is cities.

Mars, nearly full: rust-coloured plains, darker markings and a bright white polar cap at the top, with a thin haze along its edge and shadow creeping in on the right.

Mars

12 min 54 s of sunlight

A day on Mars runs 40 minutes longer than ours, under air with less than 1% of Earth’s surface pressure.

Jupiter and two of its moons far ahead, beyond a field of asteroids: a few close enough to show as small rocks, most only specks of light.

The Belt

22 min 52 s of sunlight

This belt is a synthetic swarm on true orbits. Its lanes open where a rock would circle the Sun three times for each of Jupiter’s orbits.

Jupiter’s cream and tan cloud bands, with the round black shadow of a moon on its left edge. A small yellow moon sits to the left of the planet.

Jupiter

44 min 6 s of sunlight

Jupiter is 142,984 kilometres across: eleven Earths would fit side by side.

Saturn half lit: its left half pale gold with faint bands, its right half in darkness. Seen edge-on, the rings cross it as a thin bright line.

Saturn

1 h 18 min 29 s of sunlight

The only planet less dense than water, at 687 kilograms per cubic metre.

Neptune, a deep blue globe with faint lighter bands and a few white clouds near its lower edge, against the Milky Way’s haze.

Ice giants

4 h 8 min 29 s of sunlight

Uranus spins on its side, its axis tipped 97.77° to its orbit. Neptune, the farthest planet, takes 165 of our years to go round the Sun.

From far outside, the Sun is a small eight-pointed star inside the thin circles of the planets’ orbits, beside the cloudy band of the Milky Way.

The Vast

10 h 4 min 23 s of sunlight

Past Neptune, sunlight has already travelled for more than four hours. It keeps going, out into the Milky Way.

Enter the Observatory See it to scale

Specimen Cabinet

Nine worlds, one light: each plate is drawn live by the voyage’s own engine and lit from the Sun’s side of the page.

  1. G2V

    The Sun

    —

    Surface temperature
    5,772 K
    Observe

  2. I

    Mercury

    —

    Year (sidereal)
    87.969 days
    Observe

  3. II

    Venus

    —

    Rotation (sidereal)
    5,832.6 hours, backwards
    Observe

  4. III

    Earth

    —

    Day (sidereal)
    23.9345 hours
    Observe

  5. IV

    Mars

    —

    Solar day
    24.6597 hours
    Observe

  6. V

    Jupiter

    —

    Rotation (sidereal)
    9.9250 hours
    Observe

  7. VI

    Saturn

    —

    Known moons
    274
    Observe

  8. VII

    Uranus

    —

    Axial tilt
    97.77°
    Observe

  9. VIII

    Neptune

    —

    Year (sidereal)
    60,189.018 days
    Observe

Anatomy of a World

Six layers make one Earth. Step through how the engine draws it, from the bare surface to the finished frame.

Layers, built up in order

The frame is exposed the way a camera would expose it, and the brightest light blooms softly past its edges.

Colophon

How this sky was made, what it simplifies, and where every figure comes from.

Technique

The voyage, the plates and the Earth above are drawn live in your browser, in hand-written GLSL on three.js and WebGL2. Positions are kept in 64-bit kilometres around a floating origin, with a reversed or logarithmic depth buffer, so a moon a few thousand kilometres away and a star field share one frame. Large maps stream in a few rows at a time, so none of them stalls a frame. Light runs through a high-dynamic-range pipeline: bloom, automatic exposure, AgX tone mapping and a colour grade. Earth’s air is ray-marched, moon and ring shadows fall when and where they really do, and every asteroid follows its own Kepler orbit, solved on the graphics card each frame.

What is simplified

  • Planet positions come from JPL’s approximate elements (valid 1800–2050), and the moons run on circular orbits: close, not exact.
  • Cinematic scale compresses distances and enlarges every body (the Sun 10 times, rocky worlds and moons 300 times, the giants 80 times) so the system fits a screen. The voyage ends at true scale, and the Observatory can switch to it.
  • While the voyage, a plate or the Observatory holds on one world, the others shrink back to their true size, the points of light a real sky would show.
  • A moon’s shadow on its planet is drawn as large as the moon is drawn, so the two match; when and where it falls is the real sky’s.
  • A moon inside its planet’s shadow keeps a faint trace of light on its sunward face, so it never reads as a hole in the sky.
  • Jupiter’s Great Red Spot sits where the surface map puts it, not where the storm is today. The voyage picks a real moment of Io’s shadow on the clouds when the map’s spot faces you.
  • Sunlight fades with distance more gently than it really does, so the outer worlds stay visible.
  • The asteroid belt is a synthetic population shaped like the real one, with a denser patch along the voyage’s flight path; only Ceres, Vesta, Pallas and Hygiea follow their real orbits.
  • The air of Mars, Venus and Titan is a tuned approximation, not a measured profile, and Earth’s cloud map turns slowly over the ground as a stylised drift, not weather.
  • Europa, Ganymede and Callisto have greyscale maps, tinted toward their true colours; gaps in the Io and Callisto maps are filled from nearby terrain.
  • The Jupiter chapter moves the clock to the next moon-shadow crossing and says so; every other chapter shows the present moment.
  • The cabinet’s plates are lit from the Sun plate’s side of the page, not from where the Sun really is.
  • The colour grade is a choice; the Observatory’s Neutral setting removes it. The stills on this page, and the readouts under them, were rendered by this engine on 25 Sep 2026.

Sources

Credits and licences

Planet, Sun and sky maps by Solar System Scope (CC BY 4.0); moon maps from NASA 3D Resources. Stars from the HYG database (CC BY-SA 4.0). Type: Bodoni Moda and Martian Mono (SIL Open Font License 1.1). Engine: three.js (MIT). No generated imagery: every picture here is this engine’s own render.