The Moon's orbit is an ellipse, not a circle, so its distance from Earth swings between a closest point (perigee) and a farthest point (apogee) every 27.55 days. Drag the slider below to scrub through one cycle and watch the Moon move faster near perigee and slower near apogee - the same real distance swing behind every "supermoon" headline.
The size-comparison circles above use the extreme record perigee and apogee distances (about 356,500 km and 406,700 km) - the pair most often cited for "supermoon" claims. The animated ellipse instead uses the long-term mean perigee/apogee distances (about 363,300 km and 405,500 km), since the exact record distance shifts slightly cycle to cycle.
Supermoon Lunar Apsides 3D Explorer
Last reviewed: 2026-08-08 | Authored by the FreeToolOnline teamThe Moon does not orbit Earth in a perfect circle. Its elliptical path carries it from a closest point (perigee) to a farthest point (apogee) and back every 27.55 days. Scrub the slider below to watch that swing in 3D and see the real distance, size, and brightness numbers behind every "supermoon" headline.
Key Features
- True Kepler-ellipse motion: the Moon speeds up near perigee and slows near apogee, matching Kepler's second law, not a straight-line distance fade.
- Day-in-cycle slider + Play cycle: scrub or animate through the full 27.55-day anomalistic month, or jump straight to perigee or apogee.
- Honest supermoon math: the facts panel shows the current distance plus its apparent-size and brightness ratio against the mean distance, updated live.
- Real record comparison: a side-by-side size circle shows the widely-cited ~14% larger, ~30% brighter comparison between the closest recorded perigee and farthest recorded apogee.
- No accounts needed: runs fully in your browser; nothing is uploaded.
Two Different Numbers, on Purpose
This page deliberately shows two related but different figures. The animated ellipse uses the Moon's long-term mean perigee and apogee distances (about 363,300 km and 405,500 km) - the values that describe its orbit on average. The "record supermoon" comparison (about 356,500 km vs 406,700 km, roughly 14% larger and 30% brighter) uses the most extreme distances actually observed, because the Sun's gravity nudges the Moon's orbit slightly every cycle. Conflating the two is a common source of confusion in supermoon reporting; this page keeps them clearly labeled.
The Real Numbers
| Figure | Value |
|---|---|
| Mean perigee distance | ~363,300 km |
| Mean apogee distance | ~405,500 km |
| Mean orbital eccentricity | 0.0549 |
| Anomalistic month (perigee to perigee) | 27.55 days |
| Record closest perigee | ~356,500 km |
| Record farthest apogee | ~406,700 km |
| Record size/brightness swing | ~14% larger, ~30% brighter |
Privacy + How It Runs
The Supermoon Lunar Apsides 3D Explorer runs entirely in your browser using WebGL and the vendored three.js engine. No data is sent to any server. Earth, the Moon, and the orbit ellipse are generated in code (procedural geometry) and positioned each frame by solving Kepler's equation for the current day in the cycle - all calculations happen on your device.
The Space 3D collection also includes Apsidal Precession 3D (how the ellipse's orientation itself slowly rotates over centuries, a different reader task from this page's within-one-orbit distance swing) and Moon Phases 3D (the Moon's lit-fraction cycle, driven by illumination angle rather than distance).
Frequently Asked Questions
What exactly is a supermoon?
A supermoon is a full moon (or new moon) that happens close to perigee, the Moon's closest point to Earth in its elliptical orbit. It's not an official astronomical term - there's no single agreed cutoff - but the closest supermoons of the year appear roughly 14% larger and 30% brighter than the farthest full moons near apogee.
Why does the exact record distance change every year?
The Sun's gravity constantly tugs on the Moon's orbit, slightly stretching or shrinking each individual perigee and apogee. The ellipse animated on this page uses the long-term mean distances (about 363,300 km and 405,500 km); the actual closest or farthest point in any given year can differ by a few thousand kilometers from that mean, which is why the widely-cited "14% larger, 30% brighter" figure uses the observed record extremes instead.
Is the Moon actually changing size?
No. The Moon's own diameter never changes. What changes is its distance from Earth, which changes how large it appears in the sky - the same physical effect as any object looking smaller as it moves farther away.
Why does the Moon move faster near perigee in the animation?
This follows Kepler's second law: a body in an elliptical orbit sweeps out equal areas in equal time, so it must move faster when it's closer to the body it orbits and slower when it's farther away. The scene solves Kepler's equation for the current day to place the Moon correctly, so the speed change you see is a real feature of elliptical orbits, not an animation trick.
How is this different from the Apsidal Precession 3D page?
This page shows the distance swing within a single 27.55-day orbit - perigee to apogee and back. Apsidal Precession 3D shows a slower, separate effect: the orientation of the whole elliptical orbit itself slowly rotating over roughly 8.85 years, due to Earth's slightly non-spherical gravity and the Sun's pull.
Does distance affect the Moon's phase?
No, distance and phase are independent. A supermoon can be a full moon, new moon, or any other phase - "supermoon" describes closeness to perigee, while the phase (new, crescent, full, and so on) depends on the Sun-Earth-Moon angle, covered on the separate Moon Phases 3D page.