Build a Real-Time Solar System in OpenCode

Updated 10 November 2026 · Standard formula, shown below

Yes—you can build a real-time solar-system visualization with free AI models through OpenCode, provided you have access to a compatible model and can run a local web project. The model can help write and revise the code, but you still need to choose the astronomy data, define what “real time” means, and check that the display is scientifically honest.

What “Real-Time Solar System” Means

A solar-system scene can look animated without showing the planets’ current positions. A loop that moves each planet around a circular track at an arbitrary speed is a simulation, not necessarily an ephemeris: a calculated position for a specified date and time. Decide which you want before asking an AI model to build the project.

Animated illustration: Planets move to communicate orbital order and relative motion. It can be useful for learning, but should be labeled as illustrative.
Date-driven model: Positions are calculated for a selected date and time using a stated orbital model or ephemeris source.
Live-data display: The page updates its time continuously and recalculates positions. “Live” here usually means the clock advances; it does not mean astronomers are streaming a new measurement of every planet’s location.

There is no single correct visual scale for every purpose. Planet sizes, distances, and orbital periods differ enormously, so showing the planets large enough to see while also preserving distances is impractical on an ordinary screen. A useful educational display makes that compromise explicit.

What OpenCode and a Free Model Contribute

OpenCode is an AI coding agent interface that can work with configured language models and a project’s files. It can help scaffold a web app, explain code, implement controls, and respond to errors. “Free” depends on the model and how it is offered: some providers have free access limits, while local models may avoid per-request charges but need suitable computer resources. Access terms and availability can change.

The coding agent is not itself an astronomy database or a guarantee of correctness. A model may produce plausible-looking orbital code with mistaken units, incorrect constants, or an oversimplified orbit. Treat generated code as a draft: ask it to identify its assumptions, inspect the formulas, and compare a few results with a reputable reference or established ephemeris tool.

A Practical Build Workflow

Start with a small, testable scope. For example, build a browser-based scene that displays the Sun and eight planets, lets a viewer pause or change the simulated date, and identifies its scale and data source. Then ask the model for one feature at a time rather than requesting a complete planetarium in a single prompt.

Create a project and state the goal. Ask for a minimal web app, name the framework only if you have a preference, and specify whether the first version is an illustrative animation or a date-based model.
Request a file plan before implementation. Have the agent explain which files it intends to create and what each does. Review proposed changes before accepting them, especially commands that install packages or alter project files.
Build the rendering first. Add the Sun, labeled planets, and orbit paths. Make the layout usable on narrow screens and provide a way to identify objects without relying on color alone.
Add time controls and motion. Separate the simulation timestamp from the computer’s current clock. Include pause, speed, and reset controls, and make it clear when time is being accelerated.
Choose and implement position data. For a rough educational model, use documented orbital elements and state the approximation. For accurate positions, use a suitable ephemeris or a service that provides them; check its documentation, units, coordinate frame, and date range.
Run and verify the app. Follow the project’s run instructions, inspect the browser console for errors, and test dates, resizing, labels, and controls. Ask the agent to fix specific observed issues rather than accepting a broad rewrite.

How the Orbital Display Works

A basic two-dimensional orbit model often begins with orbital elements: parameters describing an orbit’s size, shape, tilt, and orientation at an epoch. To calculate a planet’s approximate position at another time, code advances the mean anomaly using the orbital period, solves Kepler’s equation for eccentric anomaly, and transforms the resulting orbital-plane coordinates into the chosen display frame.

That outline hides important details. Orbital elements change over time, coordinate systems need consistent definitions, and a planet’s apparent position as seen from Earth differs from its heliocentric position. A three-dimensional scene must also decide how to map astronomical coordinates into screen coordinates. If the project uses a library or data service, read what its values represent instead of assuming “position” means a view from Earth.

For a first project, a useful compromise is to calculate approximate positions for a chosen date, show the epoch or data source, and describe the scene as a simplified model. If the goal is visual storytelling rather than positional accuracy, use animation and label it accordingly.

Common Problems and Accuracy Checks

Everything moves too fast or too slowly: Check whether time is measured in seconds, days, or years, and whether the animation speed multiplies the simulated clock consistently.
Planets appear in the wrong places: Verify the epoch, angle units, direction of rotation, and coordinate transformations. Degrees-versus-radians errors are especially common.
The scene looks “wrong” despite correct calculations: The display may exaggerate planet sizes or compress distances. Add a visible note such as “not to scale” and avoid implying that the layout is a literal map.
Positions disagree with another source: Compare the same timestamp, observer, coordinate frame, and definition of position. Different sources may report heliocentric, geocentric, or apparent coordinates.
The page freezes or behaves inconsistently: Recalculate on a controlled timer, avoid unnecessary work on every animation frame, and check for repeated event handlers or state updates.

Do not describe a model as precise merely because it animates smoothly. Accuracy depends on the underlying data and transformations, not visual polish. If exact observing positions matter, use a recognized ephemeris source and verify its stated precision and limitations.

Costs, Privacy, and Responsible Use

A no-cost setup is possible, but it is not automatically cost-free in every sense. Hosted model access may have usage limits or require an account; local inference can require substantial memory and processing. A project may also use packages, fonts, map tiles, or astronomy data with their own licenses and terms. Check those conditions before publishing or redistributing the app.

Keep API credentials out of public source code. If a model provider or data service requires a secret key, follow its recommended method for storing it; a key embedded in a public browser app can be copied by visitors. Also review commands suggested by an agent before running them, and do not give an agent access to files or services it does not need.

Frequently Asked Questions

Can OpenCode build a solar-system app with no coding experience?
It can help generate and explain a starter project, but you still need to run it, review changes, troubleshoot errors, and make decisions about data and accuracy. Basic familiarity with project files and a terminal makes the process easier.

Are free AI models good enough for this project?
Many models can assist with standard web-app tasks, but capability and free access limits vary. Test a small feature first, and independently verify astronomy calculations rather than relying on model confidence.

Does “real time” mean the planets’ positions are exact?
No. It may simply mean the displayed clock advances and the scene updates. Exactness depends on the ephemeris or mathematical model, the observer and coordinate frame, and the time being evaluated.

Can I make the planets and their distances to scale?
Not meaningfully in a compact screen view while keeping every planet visible. Planet sizes and orbital distances span very different scales, so most visualizations enlarge planets, compress distances, or provide separate zoom levels.

Do I need a paid API?
Not necessarily. An illustrative animation or a model based on published orbital parameters can run locally. A hosted ephemeris service may be convenient for more accurate positions, but check its access limits, documentation, and terms.

Method: the standard formula for this calculation, rounded as each result states. See how the calculators work or report an error.