A dwarf planet, a double world, and the only one of these anybody has visited exactly once. Where it is right now, how big and how heavy, what goes round it, and what is still unexplained.
Turning here at one rotation every 12 seconds, which is 45,988 times real speed. What is not sped up: which way it turns — backwards, and that is real, how far the axis leans, and how its day compares with every other planet's. The bright patch is Sputnik Planitia at roughly its real place — it faces away from Charon — and the rest is schematic.
Fri, August 7, 2026
——
Show:
flat
—
Jump to
Distances from the sun are in AU — one AU is the Earth’s average distance, 149,597,870 km — and the angle is where the body sits around its orbit, measured from the March equinox direction.
The mass is worked out from Pluto’s gravitational parameter and the gravity from that and its radius; the year comes from Kepler’s third law and the width is the same figure the simulator draws with. None of them is typed in beside the picture, so none of them can disagree with it.
Pluto has 5 confirmed moons. Every distance and period here is real, and they are not independent: each pair has to satisfy Kepler’s third law against Pluto’s mass, which is how this table is checked rather than trusted.
| Moon | Distance | Orbit | Width | |
|---|---|---|---|---|
| Charon | 19,591 km | 6.39 d | 1,212 km | Half Pluto across and an eighth its mass — the two are locked face to face and orbit a point outside them both |
| Styx | 42,656 km | 20.2 d | 16.0 km | Tumbling, not locked: the gravity here is a moving pair, not a point |
| Nix | 48,694 km | 24.9 d | 50.0 km | Its spin is chaotic — its day length changes unpredictably |
| Kerberos | 57,783 km | 32.2 d | 19.0 km | Darker than the others, and found by Hubble in 2011 |
| Hydra | 64,738 km | 38.2 d | 65.0 km | The outermost, and the far edge of this view |
↺ marks a moon going round backwards. Watch this system move →
Both planets are moving, so the gap between them swings enormously — and the closest approaches are not all equal, because the orbits are ellipses rather than circles. These are the next four, solved from the orbits rather than looked up.
Click a date to take the simulator there. These are minimum-distance moments, which fall near — but not exactly on — opposition.
Every one of these is genuinely unsettled — not simplified for the page, not waiting on a textbook update.
Sputnik Planitia sits almost exactly on the line between Pluto and Charon, which is where a heavy patch would end up if the crust could slide — and a subsurface ocean is the most natural way to make that patch heavy. It is strong circumstantial evidence and not a measurement; nothing has sounded the interior.
It was expected to collapse as Pluto receded past its 1989 perihelion, and instead the pressure rose for two decades before starting to fall. How much survives at aphelion, 49 AU out, has not been observed — nobody has watched Pluto through a full 248-year orbit.
A giant impact that made Charon is the standard answer, with the small four condensing from the debris. It accounts for the mass ratio and the tidy, near-circular, coplanar orbits, but not for every detail of their sizes and spacings.
Findings reviewed August 2026. Space science moves; a date on a finding is part of the finding.
Inward: Neptune. Or go back to the whole system, where every planet is on screen at once.
The date, the zoom, the span, the speed, the layers and any flight path are all in the address bar, so copying the URL shares exactly what is on screen. Set it up above, then take the link — it is the quickest way to hand a class one specific thing to look at.
This one is about the whole system. If the question is where the sun and the moon are from where you are standing — what time the sun comes up, why tonight's moon is the shape it is — that is the Sun, Earth & Moon movement simulator, which has a page for every city and a slider over a day, a week or a month.
Also: the classroom guide · sunrise & sunset by city · moon phase & moonrise · lunar eclipses · how the positions are worked out
Is there an ocean under the ice? Sputnik Planitia sits almost exactly on the line between Pluto and Charon, which is where a heavy patch would end up if the crust could slide — and a subsurface ocean is the most natural way to make that patch heavy. It is strong circumstantial evidence and not a measurement; nothing has sounded the interior.
Does the atmosphere freeze out completely as it moves away from the sun? It was expected to collapse as Pluto receded past its 1989 perihelion, and instead the pressure rose for two decades before starting to fall. How much survives at aphelion, 49 AU out, has not been observed — nobody has watched Pluto through a full 248-year orbit.
How did it get five moons? A giant impact that made Charon is the standard answer, with the small four condensing from the debris. It accounts for the mass ratio and the tidy, near-circular, coplanar orbits, but not for every detail of their sizes and spacings.