The planets on their real orbits, moving. Drag through a month, a year, a decade or a century; zoom from Jupiter’s moons all the way out to Neptune; switch on the asteroid belt, the comets, and the flight path to Mars.
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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.
Each one carries its own moon system, its physical figures worked out from its mass rather than copied in, the open questions about it, and what has been learned lately.
A rocket cannot point at Mars and fire. It has to leave Earth on an orbit around the sun whose far side touches Mars’s orbit — half an ellipse — and it has to leave at the moment when Mars 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 25.0 months.
Turn on Flight path to Mars above to see the ellipse, where Mars 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.
The solar system does not fit in one frame, and the reason is a ratio. What decides whether you can see anything is how many times bigger the outermost drawn orbit is than the innermost one:
So each rung is a view where something is legible, rather than a smooth zoom that spends most of its travel in frames where nothing is. The outermost rung keeps the inner four as a labelled knot on purpose — that is the shape of the solar system, and it is the part every evenly-spaced textbook diagram hides.
Everything drawn here is a set of concentric circles, and a circle in a widescreen frame is limited by the short side — the corners hold nothing. Squaring the frame at the same height buys about 40% more drawing radius, which on the outer rungs is the difference between Mercury’s orbit being four pixels wide and six.
The orbits are to scale within each view. The planets are not, and cannot be: at the Saturn view Jupiter would be 0.077 of a pixel across and Earth 0.0070. The dots are sized to be seen, not measured.
The one exception is Earth & the Moon, and it is worth looking at for that reason alone: it is the only view on this site that is to scale in size and distance at the same time. The moon really does sit about 30 Earth-diameters away — far further than almost every diagram draws it, and close enough to fit on a screen.
On a moon system view, the planet’s own disc is to scale against its moons’ orbits — so Saturn’s rings really are that wide compared with Titan’s orbit, and Phobos really is that close to Mars. The moons themselves are drawn oversize by a factor the picture prints, because at the zoom where Callisto’s orbit fills the frame, Ganymede is half a pixel across.
| Span | Mercury | Earth | Jupiter | Saturn | Neptune |
|---|---|---|---|---|---|
| Month | 123° | 30° | 2° | 1° | 0° |
| Year | 4.2 laps | 360° | 30° | 12° | 2° |
| Decade | 42 laps | 10.0 laps | 303° | 122° | 22° |
| Century | 415 laps | 100 laps | 8.4 laps | 3.4 laps | 218° |
Which is why the zoom, the span and the speed belong together. A month is the right span for Mercury and means nothing for Neptune; a century sends Mercury round 415 laps — an unreadable blur — while Neptune still has not finished a single lap, because one Neptune year is 165 of ours. The speed slider is there so you can slow a century down until the outer planets separate, or run a month fast enough to see Mercury move.
Every one of these is genuinely unsettled — not simplified for the page, not waiting on a textbook update.
A cluster of distant objects beyond Neptune share an orbital orientation that looks non-random, and one explanation is an unseen planet of roughly 5–10 Earth masses on a very wide orbit. The competing explanation is that we found those objects with telescopes that were pointed at particular parts of the sky at particular times, and the clustering is in the searching rather than in the sky. Neither has been settled, and the Vera C. Rubin Observatory's ten-year survey is the instrument most likely to settle it.
The visible surface is about 5,500 °C. The thin corona above it is one to three million degrees. Heat is not supposed to flow that way. Magnetic reconnection and wave heating are the leading candidates, and the Parker Solar Probe was built to fly into the corona and find out — it has now been through it repeatedly, and the answer is still being argued over.
Planets between the size of Earth and Neptune are the commonest kind found around other stars, and our system does not have one — there is a gap between Earth and Neptune where most systems put their most typical planet. Jupiter's early migration inward and back out is the usual explanation, but that migration is itself a model, not an observation.
They did not form where they now sit. Models in which the giant planets shift outward and inward — dragging small bodies around, emptying part of the asteroid belt and scattering the Kuiper belt — reproduce a great deal of what we see. Which version happened, and when, is not agreed.
Findings reviewed August 2026. Space science moves; a date on a finding is part of the finding.
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 the view jump between zoom levels instead of scrolling smoothly? Because the solar system will not fit in one frame. Out to Mars the outermost orbit is only about 4 times the innermost, and everything is separable. Out to Saturn it is 27 times and the inner four are a tight knot. Out to Neptune it is 81 times: Mercury's whole orbit is 5.2 pixels across and Earth's is 13. Each rung of the ladder is a view where something is legible; a smooth zoom would just pass through a lot of frames where nothing is.
Can I see the moons of the other planets? Yes — each of the five planets that has large moons gets a view of its own, where the frame is the moon system rather than the solar system. The orbits, the periods, the sizes and the direction of travel are all real, and the planet's own disc is to scale against them. What is not solved for is where each moon sits on its orbit at a given moment, and the picture says so: watch Io lap Europa twice while Europa laps Ganymede twice, which is a real resonance, rather than reading it as tonight's sky.
Are the planets drawn to scale? The ORBITS are, within each view. The planets themselves cannot be: at the Saturn view, Jupiter — the largest planet — would be 0.077 of a pixel across, and Earth 0.0070. So the dots are legibility sizes, not measurements. The exception is the Earth and Moon view, which is to scale in both size and distance at once.
When is the next launch window to Mars? Every launch window on this site is solved from the orbits when the page loads, not written into it — the answer for Mars right now is November 4, 2026, with an arrival 265 days later. Windows to Mars come round roughly every 26 months, because that is how long it takes Earth to lap Mars and line the two orbits up again.
Where is the asteroid belt, and why does it have gaps? Between Mars and Jupiter, from about 2.06 to 3.28 AU. The gaps are Jupiter's doing: an asteroid whose orbital period is a simple fraction of Jupiter's gets the same tug at the same point over and over until it is pushed out. This page computes every edge and every gap from Jupiter's own orbit rather than drawing them from a remembered number, which is why they land on the Kirkwood gaps at 2.50, 2.82 and 2.96 AU.
How accurate are the positions? The planets come from Keplerian elements with per-century rates — the standard approximate-positions method — good to a few arcminutes over 1800–2050, which is far finer than this picture can show. The comets are published osculating elements propagated as a two-body orbit, which is right about where in the system a comet is and not right to the day: a real comet is pulled about by the planets and shoved by its own outgassing. None of this is an ephemeris.
Can I share a particular date? Yes. The date, the zoom level, the span, the speed, the belt and comet layers and any flight path are all in the address bar, so copying the URL shares exactly what is on screen, and the builder near the bottom writes one for you.