Distances to scale · bodies enlarged for visibility
Loading orbital data and the night sky…
Start from a preset, or change a body in the current simulation. Changes pause time so you can inspect the starting point.
Add velocity in the fixed J2000 ecliptic frame. X points toward the vernal equinox; Z points north of the ecliptic.
A scenario file stores all masses, positions, velocities and simulation time. Import it to resume, or reset to replay from that saved point.
Choose a bright catalog star and turn the observatory toward its J2000 position.
OpenNGC galaxies, clusters, nebulae and other objects use catalog coordinates. The three large nearby galaxies have schematic angular shapes.
Markers follow bundled NASA/JPL Horizons reference trajectories. Scenario changes do not alter them.
Traditional Western line patterns are connected between the stars at their catalog distances, revealing how the familiar shape changes away from the Sun.
Zoom out past 50,000 AU to reveal stars at their catalog distances. The guide rings and labels frame the nearest 40 light-years; the Gaia cloud continues to about 13,046 light-years.
The Sun, eight planets and the Moon interact through Newtonian gravity. Initial barycentric positions and velocities come from NASA/JPL DE440 at 15 September 2026, 00:00 TDB. Mars and the outer planets represent their system barycenters and include their moons' masses; Earth and Moon are separate.
Time acceleration runs more 11.25-minute integration steps, never larger ones. Orbit guides are instantaneous two-body ellipses, not predicted trajectories. The simulation pauses at contact or at ±100 years from the initial epoch.
The complete HYG v4.1 catalog, excluding its Sun row, supplies the named-star background, B−V colors and constellation references in the J2000 frame. The visible magnitude filter defaults to 6.5. OpenNGC adds cataloged galaxies, clusters and nebulae.
At interstellar scale, a deterministic one-million-source Gaia DR3 subset forms the main 3D cloud out to 4,000 parsecs (about 13,046 light-years). It requires positive parallax with signal-to-noise of at least 10 and RUWE below 1.4; displayed distance is the simple inverse parallax. BP−RP color is available for 993,867 selected sources and drives a stronger blue-to-amber display mapping; the remaining 6,133 use a neutral fallback. HYG distance-bearing stars remain as named references. Gaia coordinates use reference epoch J2016.0. Proper motion, parallax zero-point correction, light-time and relativistic aberration are omitted.
Orbital distances are to scale. By default, small bodies have a minimum display size; choose True body sizes for physical radii. Explore a planet to see its textured surface. Surface rotation, pole directions, rings and illumination are illustrative; texture longitude is not tied to an accurate prime meridian. Lighting uses artistic exposure so outer planets remain visible.
The model excludes relativity, tides, oblateness, asteroids and other individually modeled moons. There is no atmosphere or impact model. Altered masses and impulses are hypothetical interventions. Conservation diagnostics measure numerical drift from the current scenario's starting energy, not agreement with the real sky.
Drag to orbit · scroll or pinch to zoom · right-drag or two-finger drag to pan. Select a planet from the list or its label. Space pauses time outside form controls. U toggles the interface for a clear view. Escape closes a dialog. The five optional soundtrack variations are original procedural Web Audio compositions generated locally after you press play; they contain no sampled or streamed music.
gaia_source_lite