# Pax Abyssi galaxy data release r1: attribution and licence

This release is baked from the Pax Abyssi game's star catalogue and system exports.

## Star data (CC BY-SA 4.0)

The star positions, magnitudes, colours, designations and catalogue columns in
`stars/`, `catalog/`, `names.json`, `xref.bin` and the `star` block of every file in
`sys/` derive from the **HYG Database** by David Nash (astronexus.com, github.com/astronexus/HYG-Database),
licensed under the Creative Commons Attribution-ShareAlike 4.0 International licence
(https://creativecommons.org/licenses/by-sa/4.0/). Under ShareAlike, these star data
files are offered under the same licence. HYG compiles:

- the Hipparcos Catalogue (ESA 1997) and its new reduction (van Leeuwen 2007);
- the Yale Bright Star Catalog, 5th edition (Hoffleit and Warren 1991);
- the Gliese Catalog of Nearby Stars, 3rd edition (Gliese and Jahreiss 1991).

Pax Abyssi's catalogue (HYG v3, "pax_abyssi_hyg_v3") adds corrections from:

- **Gaia DR3**: this work has made use of data from the European Space Agency (ESA)
  mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing
  and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium).
  Funding for the DPAC has been provided by national institutions, in particular the
  institutions participating in the Gaia Multilateral Agreement. Gaia data: CC BY-SA 3.0 IGO.
- **XHIP**, the Extended Hipparcos Compilation (Anderson and Francis 2012, Astronomy
  Letters 38, 331): spectral types, metallicities and ages.
- **WDS**, the Washington Double Star Catalog (Mason et al. 2001, US Naval Observatory).

## Known exoplanets

Known planets in `catalog/*.json` (`exo`) come from the NASA Exoplanet Archive
(Planetary Systems table, snapshot 2025-06-29): this research has made use of the
NASA Exoplanet Archive, which is operated by the California Institute of Technology,
under contract with the National Aeronautics and Space Administration under the
Exoplanet Exploration Program.

## Solar System

Sol's planetary elements are J2000 mean elements (JPL, Standish); moon elements are
fitted to JPL Horizons; masses are JPL GM values (DE440 and satellite ephemerides).

## Generated content

Every planet, moon and belt outside Sol, and every value marked Generated (G), is the
output of the Pax Abyssi system generator (a port of sfb2's physics-first pipeline).
It is not observational data. Provenance badges: M measured, D derived by a named
formula from measured values, G generated by the simulation, L lore.

## Milky Way backdrop

`milkyway/*.png` is rendered from the game's published Milky Way model (Data/MilkyWay.json),
which cites Juric et al. 2008, Reid et al. 2019, Hunter et al. 2024, Sormani et al. 2022,
GRAVITY Collaboration 2021 and Bennett and Bovy 2019 among others.