> For the complete documentation index, see [llms.txt](https://jewels86.gitbook.io/axinite/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://jewels86.gitbook.io/axinite/axtools/guides/solar-system/writing-the-initial-template-file.md).

# Writing the Initial Template File

To simulate our own system, we'll need to write a template file for it first. You can include any number of planets, in any formation you want. You can set the `limit` to some random value for now, as we don't know how long it'll take each planet to finish it's orbit.

Here''s an example template file:

```json
{
    "name": "my-solar-system",
    "limit": "3yr",
    "delta": "1hr",
    "t": 0,
    "bodies": [
        {
            "name": "Sun",
            "mass": 1.989e30,
            "radius": 6.95e8,
            "r": [[0, 0, 0]],
            "v": [[0, 0, 0]]
        },
        {
            "name": "Earth",
            "mass": 5.972e24,
            "radius": 6.371e6,
            "r": [[1.496e11, 0, 0]],
            "v": [[0, 0, 2.98e4]]
        },
        {
            "name": "Moon",
            "mass": 7.342e22,
            "radius": 1.737e6,
            "r": [[1.499844e11, 0, 0]],
            "v": [[0, 0, 3.082e4]]
        }
    ]
}
```

Be sure that you set the limit to a number that will surely be *more* than the longest orbital period, so `axana` can correctly find a good limit.