Tipped over on its side, visited once, and still mostly unexplained. Where it is right now, how big and how heavy, what goes round it, and what is still unexplained.
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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 Uranus’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.
Uranus has 28 confirmed moons, of which the 6 below are large enough to be worth drawing. The rest are mostly a few kilometres of captured rubble on distant, tilted orbits. Every distance and period here is real, and they are not independent: each pair has to satisfy Kepler’s third law against Uranus’s mass, which is how this table is checked rather than trusted.
| Moon | Distance | Orbit | Width | |
|---|---|---|---|---|
| Puck | 86,004 km | 18.3 h | 162 km | Dark, and probably rubble from a shattered earlier moon |
| Miranda | 129,900 km | 1.41 d | 472 km | A cliff 20 km high — the tallest known anywhere |
| Ariel | 191,020 km | 2.52 d | 1,158 km | The brightest and youngest-looking surface of the five |
| Umbriel | 266,000 km | 4.14 d | 1,169 km | The darkest, with one unexplained bright ring near its equator |
| Titania | 435,910 km | 8.71 d | 1,577 km | The largest, with canyons 1,600 km long |
| Oberon | 583,520 km | 13.5 d | 1,523 km | Craters floored with something dark that nobody has identified |
↺ 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.
A single Earth-sized impact is the standard answer, but a single impact should also have scrambled the moons, and instead they orbit neatly around the tilted equator — which suggests whatever happened, happened while a disc was still there to re-form them. Several smaller impacts, or a lost massive moon, are the alternatives.
The two planets are near twins in size and composition, and Neptune pours out internal heat while Uranus barely does. Either Uranus lost its internal heat in the same event that tipped it, or something in its interior stops heat convecting out. Neither has been demonstrated.
A 2024 reanalysis found that the flyby happened within days of a rare solar-wind compression that squashed the magnetosphere to about a fifth its usual volume. Much of what textbooks say about Uranus's magnetic environment may therefore describe an unusual few days rather than the planet — an unusually clean example of how thin one flyby's worth of data is.
Findings reviewed August 2026. Space science moves; a date on a finding is part of the finding.
Inward: Saturn. Outward: 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
What knocked it over? A single Earth-sized impact is the standard answer, but a single impact should also have scrambled the moons, and instead they orbit neatly around the tilted equator — which suggests whatever happened, happened while a disc was still there to re-form them. Several smaller impacts, or a lost massive moon, are the alternatives.
Why is it so much colder than Neptune? The two planets are near twins in size and composition, and Neptune pours out internal heat while Uranus barely does. Either Uranus lost its internal heat in the same event that tipped it, or something in its interior stops heat convecting out. Neither has been demonstrated.
Was Voyager 2 unlucky? A 2024 reanalysis found that the flyby happened within days of a rare solar-wind compression that squashed the magnetosphere to about a fifth its usual volume. Much of what textbooks say about Uranus's magnetic environment may therefore describe an unusual few days rather than the planet — an unusually clean example of how thin one flyby's worth of data is.