Two and a half times the mass of everything else in the solar system put together. 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 Jupiter’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.
Jupiter has 97 confirmed moons, of which the 9 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 Jupiter’s mass, which is how this table is checked rather than trusted.
| Moon | Distance | Orbit | Width | |
|---|---|---|---|---|
| Metis | 127,690 km | 7.1 h | 43.0 km | Inside the main ring, and feeding it |
| Adrastea | 128,690 km | 7.2 h | 16.4 km | The dust knocked off these two IS the main ring |
| Amalthea | 181,366 km | 12.0 h | 167 km | Red, potato-shaped, and radiating more heat than it receives |
| Thebe | 221,900 km | 16.2 h | 98.6 km | Its dust makes the outer gossamer ring |
| Io | 421,700 km | 1.77 d | 3,643 km | The most volcanically active body known — squeezed by Jupiter and by Europa |
| Europa | 671,034 km | 3.55 d | 3,122 km | A saltwater ocean under an ice shell, and more liquid water than Earth has |
| Ganymede | 1,070,412 km | 7.15 d | 5,268 km | The largest moon in the solar system — bigger than Mercury — and the only one with its own magnetic field |
| Callisto | 1,882,709 km | 16.7 d | 4,821 km | The most cratered surface known: nothing has resurfaced it in four billion years |
| Himalia | 11,451,000 km | 250.6 d | 140 km | A captured asteroid, 27 times further out than Io |
↺ 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.
A rocket cannot point at Jupiter and fire. It has to leave Earth on an orbit around the sun whose far side touches Jupiter’s orbit — half an ellipse — and it has to leave at the moment when Jupiter will have arrived at that far side by the time the ship gets there. That is what a launch window is, and it is why they come round only every 12.9 months.
Turn on Flight path to Jupiter above to see the ellipse, where Jupiter is on launch day, and where it will be on arrival. Click the date to fly it.
It is a minimum-energy transfer: the cheapest possible path, half an ellipse with Earth’s orbit at one end and the target’s at the other, solved against where the planets really are — so the arrival lands on the planet’s real distance from the sun and its real position on the day it gets there, not on a circle standing in for its orbit.
It is not a mission plan, and three things are left out on purpose. The orbits are treated as flat, so the real inclinations — Mars is tilted 1.85°, Jupiter 1.3° — cost a plane change this ignores. Real missions trade fuel for a faster arrival, so they leave within days or weeks of these dates rather than exactly on them. And anything going past Jupiter usually steals speed from a planet on the way instead of buying it with fuel, which changes both the date and the path.
What it gets right is the thing worth teaching: why the window exists, why it comes round on the cadence it does, and why the cost of the trip is set by where two planets happen to be rather than by how far apart they are.
Every one of these is genuinely unsettled — not simplified for the page, not waiting on a textbook update.
The mechanism is fairly well settled — dust knocked off four small inner moons, held briefly in orbit, spiralling in and being replaced. What is not settled is why the giants all have rings and the rocky planets have none, and why Jupiter's are dust while Saturn's are ice boulders. Ring systems may be a phase every giant goes through, in which case Saturn's are a snapshot of something Jupiter has already finished.
Juno's gravity measurements do not fit a planet with a clean rocky core, nor one with none. They fit a 'fuzzy' core: heavy elements smeared through the inner half of the planet rather than concentrated. That is difficult to produce in formation models unless something enormous hit Jupiter early on, and it has not been explained.
Juno found that the belts and zones extend about 3,000 km down — far deeper than expected — before the interior starts rotating as a solid body. What sets that depth, and what the flows look like below the clouds, is unresolved.
Findings reviewed August 2026. Space science moves; a date on a finding is part of the finding.
Inward: Mars. Outward: Saturn. 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
Why does Jupiter have rings, and why are they so faint? The mechanism is fairly well settled — dust knocked off four small inner moons, held briefly in orbit, spiralling in and being replaced. What is not settled is why the giants all have rings and the rocky planets have none, and why Jupiter's are dust while Saturn's are ice boulders. Ring systems may be a phase every giant goes through, in which case Saturn's are a snapshot of something Jupiter has already finished.
Is there a core in there? Juno's gravity measurements do not fit a planet with a clean rocky core, nor one with none. They fit a 'fuzzy' core: heavy elements smeared through the inner half of the planet rather than concentrated. That is difficult to produce in formation models unless something enormous hit Jupiter early on, and it has not been explained.
How deep does the weather go? Juno found that the belts and zones extend about 3,000 km down — far deeper than expected — before the interior starts rotating as a solid body. What sets that depth, and what the flows look like below the clouds, is unresolved.