STARS — three distinct astronomical views (local implementation)

1. Earth sky
HYG stars and their license: /star-data-credits.txt and /hyg-LICENSE.txt.
The Galactic plane is converted from Galactic coordinates to J2000 equatorial
coordinates, then uses the SAME precession, sidereal-time and horizon projection
as the stars. The glow between Galactic latitude -12 and +12 degrees is an
illustrative band: widths, brightness and color are NOT measured surface
brightness, NOT a photograph and NOT a simulation of naked-eye visibility.
It is labelled as schematic and can be disabled without removing the stars.
No stochastic dust map or random stars are used.
Coordinate convention background:
https://docs.astropy.org/en/stable/api/astropy.coordinates.Galactic.html
Standard Galactic pole: J2000 RA 192.85948 deg, Dec 27.12825 deg.
Galactic centre direction (l=0,b=0): approximately RA 266.405 deg, Dec -28.936 deg.
Implementation is independent matrix-vector arithmetic, not copied library code.

2. External Milky Way structural illustration
Independent SVG drawing based on the barred spiral / bulge / disk / spiral arm
structure described by NASA. The Sun is marked near the Orion Spur, about
26,000 light-years from the centre, compared with a disk diameter of roughly
100,000 light-years. These are rounded educational dimensions, not precision
estimates. Arm curves, phase, thickness and orientation are schematic, not a
fitted model or measured 3D catalog. Two principal arms and two subsidiary arms
are shown for orientation. No random point cloud is represented as measured data.
https://science.nasa.gov/resource/the-milky-way-galaxy/
https://science.nasa.gov/universe/galaxies/
The NASA page's original illustration credit is NASA/JPL-Caltech/R. Hurt
(SSC/Caltech). That illustration is NOT copied here; it is a scientific reference.

Optional Earth-view photographic reference:
The Milky Way panorama, ESO image eso0932a (2009).
Full unaltered credit: ESO/S. Brunier
https://www.eso.org/public/images/eso0932a/
Downloaded official screensize JPEG:
https://cdn.eso.org/images/screen/eso0932a.jpg
License: CC BY 4.0, https://creativecommons.org/licenses/by/4.0/
Terms: https://www.eso.org/public/outreach/copyright/
Stored unchanged as /milky-way-eso.jpg, displayed responsively with adjacent
visible credit. This is the published small image, NOT the restricted full
800-million-pixel original. The photo is a stitched all-sky view from Earth,
not an exterior photograph of our galaxy. It is NOT used for coordinate
registration with the star catalog: no WCS calibration is claimed.
If the image fails, the local diagrams and all textual content remain available.

3. Solar-system structure
Independent SVG illustration: Sun + eight planets in correct radial order.
Orbital radii on screen are compressed and body sizes exaggerated; the orbits
are circular and coplanar. The initial phases are arbitrary for legibility.
No orbit or body texture is a photograph. Colors and Saturn's ring are schematic.
Optional demonstration advances 10 model days per real second with the listed
sidereal periods. It is NOT an ephemeris and not tied to the night-sky UTC clock.
The demonstration is paused by default, respects reduced motion and background
visibility, and is disabled if the user's night-sky pause preference is enabled.

Numerical parameters (rounded facts):
Mean radii and sidereal orbital periods:
https://ssd.jpl.nasa.gov/planets/phys_par.html
This page retains detailed original references (Seidelmann 1992, Archinal et al.
2018 and related studies). Orbital periods use Julian years of 365.25 days.
Nominal semimajor axes near J2000, rounded from the JPL table:
https://ssd.jpl.nasa.gov/planets/approx_pos.html
Reference: E.M. Standish and J.G. Williams (1992), Table 1.
Earth's displayed 1 AU is an educational approximation; the JPL table uses
the Earth-Moon barycentre. The table's orbital solution is NOT implemented here.
Planet summaries: https://science.nasa.gov/solar-system/planets/
No JPL article text or third-party software source is copied.

All sources checked 2026-11-01. No paid services, API keys, geolocation
permissions, external runtime data APIs, or Stellarium/AGPL code are used.

ESO image SHA256: 9055c7a801035211706565d838a6fa52ac9e670168b788e0008bd947e55e5c0e
