Explore the Solar System Builder & Kepler's Laws
Drag planets to new orbits, change the star's mass and check Kepler's third law. Free, no signup, runs in your browser.
- Free to use
- No signup
- Nothing to install
- Runs in your browser
Illustration. Open the tool for the real thing.
See it in action
The Solar System Builder & Kepler's Laws with sample data entered and the result showing.
What is the Solar System Builder & Kepler's Laws?
Drag planets to new orbits, change the star's mass and check Kepler's third law. It runs in your browser, so a change to a setting or a drag on an object shows up at once.
Astronomers use the same law to weigh stars and find exoplanets.
3 steps to your result
Open the tool and follow along. Nothing to install.
What you get
A planet further from its star takes longer to orbit.
T² is proportional to a³ (Kepler's third law).
A heavier star makes planets orbit faster.
Drag Earth to Mars's distance and read the period.
Double the star's mass.
Put a planet very close to the star.
Used for
Pick one to see how it fits.
Earth & Space learners
Astronomy and earth-science students, and teachers who need a visual model to explain what is happening in the sky.
Try it freeTeachers
For teachers: project the Solar System Builder & Kepler's Laws on the board, let students predict the result, then run it together and test this: Double the star's mass. For students: change one thing at a time and write down what changes.
Try it freeHow it compares
A plain look at this tool next to the usual alternative.
| This simulation | Textbook diagram | |
|---|---|---|
| Interactive | Drag, tap and change settings | Fixed picture |
| Install | Nothing to install | Not needed |
| Cost | Free to use | Depends on the book |
Questions people ask
What is Kepler's third law?
The square of a planet's orbital period is proportional to the cube of its average distance from the star.
How long is a year on Mars?
About 1.88 Earth years, because Mars is 1.52 AU from the Sun.
Is the Solar System Builder & Kepler's Laws free to use?
Yes. The Solar System Builder & Kepler's Laws is free, needs no signup or download and runs in your web browser. It is part of the Earth & Space group of AZRS simulations.
Does the Solar System Builder & Kepler's Laws work on a phone or tablet?
Yes. The Solar System Builder & Kepler's Laws takes touch input as well as mouse input, so you can use its 3 adjustable settings with a finger. A larger screen makes the controls and graphs easier to read.
How do I use the Solar System Builder & Kepler's Laws?
1. In the Solar System Builder & Kepler's Laws, use the controls to change Star mass (Suns), Time speed (years per second), Distance scale. The simulation reacts instantly. 2. In the Solar System Builder & Kepler's Laws, pick an option such as Inner planets, Whole system to switch modes or load an example. 3. In the Solar System Builder & Kepler's Laws, press "Reset planets" to start, reset or change what is happening. 4. Start with this experiment: Drag Earth to Mars's distance and read the period. Drag any glowing handle, object or slider with your mouse or finger and the Solar System Builder & Kepler's Laws responds in real time. 5. Change one setting at a time and watch which readout moves, then compare it with this idea: A planet further from its star takes longer to orbit.
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Try the Solar System Builder & Kepler's Laws now
Drag planets to new orbits, change the star's mass and check Kepler's third law. Free to use.
Try it free