HYG Database

To visualize the HYG Database, imagine it as the master "address book" for every star within our immediate cosmic neighborhood. While older catalogs were like flat paper maps, HYG is the 3D GPS data that allows us to fly through space in simulators.

History and Who Made It

The HYG Database was created by David Nash, an amateur astronomer and software developer. It first appeared in the early 2000s (with the definitive version 3.0 arriving around 2014 and version 4.2 in 2025).

Nash realized that professional astronomical catalogs were often too large and technically complex for hobbyists or game developers to use. He decided to "mash up" three major historical catalogs into one clean, manageable file. The name HYG comes from the first letters of these three sources:

1. Hipparcos (The gold standard for star distances).

2. Yale Bright Star (The catalog of every star you can see with the naked eye).

3. Gliese (The catalog of stars closest to our Sun).

The Purpose

The primary goal of the HYG database is accessibility and 3D visualization.

• Coordinate Conversion: It takes "Right Ascension" and "Declination" (where a star looks like it is in the sky) and converts them into X,Y,Z coordinates (where the star actually is in space).

• Software Foundation: It is the "engine" behind almost all modern 3D space software, from Stellarium and Celestia to scientific models of the local galaxy.

• Standardization: It provides a single "ID" number for stars that might have five or six different names in other catalogs.

What Objects and How Many

The database contains stars only—no galaxies or nebulae. In version 3.0, it contains exactly 119,617 stars. This specific number represents a "complete" census of the local universe based on three criteria:

• Hipparcos Subset: 118,218 stars with high-precision distance measurements.

• Yale Bright Star Subset: 9,110 stars (all stars brighter than magnitude 6.5).

• Gliese Subset: 3,803 stars that are within 25 parsecs (about 81 light-years) of Earth.

HYG Data Summary

Database Name: HYG Database Current Version: 3.0 / 4.2 Creator: David Nash (The Astronomy Nexus) Primary File Format: Comma Separated Values (CSV) Total Objects: 119,617 stars

Data Column 1: ID (The database primary key) Data Column 2: Hip (Hipparcos Catalog ID) Data Column 3: HD (Henry Draper Catalog ID) Data Column 4: HR (Harvard Revised / Yale Bright Star ID) Data Column 5: Gl (Gliese Catalog ID) Data Column 6: Bayer (Bayer Greek letter name) Data Column 7: Flam (Flamsteed number) Data Column 8: ProperName (Common names like Sirius or Rigel) Data Column 9: RA and Dec (Position in the sky) Data Column 10: Dist (Distance from Sun in Parsecs) Data Column 11: Mag (Apparent magnitude / brightness) Data Column 12: AbsMag (Absolute magnitude / actual power) Data Column 13: Spectrum (Spectral type / temperature and color) Data Column 14: X Y Z (3D Cartesian coordinates in light-years)

Notable HYG Statistics: Star ID 0: The Sun (Sol) Star ID 1: Proxima Centauri (The closest neighbor) Star ID 2: Alpha Centauri A (The nearest Sun-like star) Max Distance: Roughly 100,000 parsecs (for stars with unknown distances) Brightest Star: Sirius (Magnitude minus 1.44)

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