# Milky Way texture sources

Made from ESA's Gaia EDR3 all-sky map, "The colour of the sky from Gaia's
Early Data Release 3 – equirectangular projection",
https://sci.esa.int/web/gaia/-/the-colour-of-the-sky-from-gaia-s-early-data-release-3-equirectangular-projection
(file `Gaia_EDR3_flux_cartesian_4k.png`, 4000 × 2000, downloaded 2026-10-20).

Credit: **ESA/Gaia/DPAC; acknowledgement A. Moitinho**

The source is licensed under Creative Commons Attribution-ShareAlike 3.0 IGO
(https://creativecommons.org/licenses/by-sa/3.0/igo/). **These files
(`brightness.png`, `colour.png`, `milkyway.json`) are licensed under the same
licence, CC BY-SA 3.0 IGO**: anyone may download, share and adapt them, also
commercially, provided they give the credit above, link the licence, say what
they changed, and share their adaptations under the same licence.

## Changes from the source

Made by `scripts/build-milky-way.py` with `scripts/milky_way.py`, which
describes each step:

- Every point source removed: stars, and the globular clusters Omega
  Centauri, 47 Tucanae and M3. The Magellanic Clouds stay.
- The grain (unresolved faint stars) removed by wavelet noise reduction, which
  softens dust filaments finer than about 10–15′.
- Colour smoothed more than brightness, and stored at a quarter of the size
  (`colour.png`, 1000 × 500).
- Brightness (`brightness.png`, 4000 × 2000, one channel) is the mean of the
  processed red, green and blue, still on ESA's display scale.
  `milkyway.json` gives the fitted conversion to real surface brightness,
  log10 S10(V) = a·s + c, calibrated against the Pioneer 10 integrated
  starlight of Leinert et al. 1998, "The 1997 reference of diffuse night sky
  brightness", A&AS 127, 1, Tables 35 and 36 (`scripts/data/pioneer10-isl.csv`).

No AI tools were used to change the image.