# Object information sources — v0.3, 24 October 2026

The bundled `web/data/object-info.json` contains 119 object entries and original
educational descriptions organized by object type. It does not use generated
answers or a network encyclopedia at runtime. The application source formats
these facts alongside the existing sky catalog and calculated observer data.

## NASA Science

89 individual pages in NASA's Hubble Messier Catalog were retrieved on
2026-10-24. Published distance, constellation, and classification fields were
transcribed as factual data. 88 contain a distance estimate; M24's page supplies
its constellation. The Hubble collection does not currently provide a page at
the expected URL for 21 Messier objects; those entries use the bundled catalog
and type explanations, with unavailable distance explicitly indicated. Each
available NASA page is linked directly in the corresponding object entry.

https://science.nasa.gov/mission/hubble/science/explore-the-night-sky/hubble-messier-catalog/

Sun, Moon, and planetary facts are rounded reference values, with NASA Science
fact-page URLs stored per object. No rapidly changing moon counts are included.
Planet radii are mean radii; the Sun's radius is approximate. A rotation period
is not the same as the interval between successive local noons. Saturn's bulk
rotation is approximate. Text is original explanatory prose, not a reproduction
of the source articles. No new photographs were downloaded for this release.

Stellar color/temperature educational reference:
https://science.nasa.gov/exoplanets/stars/

## Existing catalogs and calculations

D3-Celestial supplies fixed J2000 positions, magnitude, angular sizes, names,
Hipparcos identifiers, and B−V color indices. Existing BSD notices and original
source acknowledgements remain in this directory. It does not supply stellar
parallax, distance, age, physical radius, or full spectra in this app's subset.
Constellation names for Messier objects missing a NASA entry are calculated
from fixed J2000 coordinates using Astronomy Engine's IAU boundary lookup.

M24 (star cloud), M40 (double star), and M73 (asterism) refine the catalog's
`pos` label; M102 uses the NGC 5866 lenticular-galaxy identification already
present in the source catalog. Historical ambiguity of the M102 identification
is not resolved by this app. Physical classes can differ between catalogs;
NASA's class is shown separately from the sky catalog class when available.

Astronomy Engine 2.1.19 calculates body positions, illumination, apparent
magnitude, and Earth-center distance at the selected observation time.
AU → km: 149,597,870.7; light-time per AU approximately 499.0048 seconds.
No fixed Earth–planet distance is substituted for the ephemeris calculation.