Welcome to the HYG star database archive. The most current version of the database will always be found here.

Versions and Licensing:

Current version: HYG v4.1 (directory: hyg/CURRENT/hyg_v41.csv)

HYG 4.1 contains 1 update:

1. The following stars have a primary with a proper name, but an unnamed secondary. For consistency in labeling, in HYG 4.1, these secondaries have a name of "[primary name] B".

These names are unofficial. They are intended to make these double stars (which, in most cases, are relatively wide) show more consistent labels or names on charts that resolve the double, or lists that show both stars. Without the "B" names, labels on charts or names in lists would often look something like "Revati" and "ζ Psc", and it wouldn't always be clear that the two stars are strongly historically associated.

HIP ID	HR/Yale ID	Bayer/Flamsteed	HYG 4.1 Name
5743	362	ζ Psc	Revati B
63121	4914	α¹ Cvn	Cor Caroli B
75415	5734	μ² Boo	Alkalurops B
78821	5985	β² Sco	Acrab B
79045	6009	κ Her	Marsic B
866230	6637	ψ¹ Dra	Dziban B
92951	7142	θ² Ser	Alya B
95951	7418	β² Cyg	Albireo B
	2890	α Gem	Castor B
	4374	ξ UMa	Alula Australis B
	6402	36 Oph	Guniibuu B

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This work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

Previous versions (HYG 2.x, HYG 3.x, directories hyg/v3 and hyg/v2)

These are in the directories hyg/v2 and hyg/v3. As noted above, these have been licensed under Creative Commons BY-SA-2.5. All of these are stored as gzip (.gz) files.

General content notes

1. All stars now have both an epoch and equinox of 2000.0. In v2 of the catalog, all three primary source catalogs either had or were adjusted to equinox 2000, but all 3 had different epochs, leading to small position errors at high magnifications.
2. The Flamsteed numbers now include many that were not in the Yale Bright Star Catalog, the primary reference for these numbers in the original catalog. In particular, it now contains all valid numbers listed in "Flamsteed's Missing Stars", M. Wagman, JHA xviii (1987), p 210-223.
3. Some errors in proper motions have been corrected.
4. A few additional proper names have been added.
5. For stars in Hipparcos that are known to be variable, the variable star designations have been added. In general, stars that were merely suspected of variability ("NSV") were excluded.

Fields in the database (valid for both v3.x and v4.x):

1. id: The database primary key.
2. hip: The star's ID in the Hipparcos catalog, if known.
3. hd: The star's ID in the Henry Draper catalog, if known.
4. hr: The star's ID in the Harvard Revised catalog, which is the same as its number in the Yale Bright Star Catalog.
5. gl: The star's ID in the third edition of the Gliese Catalog of Nearby Stars.
6. bf: The Bayer / Flamsteed designation, primarily from the Fifth Edition of the Yale Bright Star Catalog. This is a combination of the two designations. The Flamsteed number, if present, is given first; then a three-letter abbreviation for the Bayer Greek letter; the Bayer superscript number, if present; and finally, the three-letter constellation abbreviation. Thus Alpha Andromedae has the field value "21Alp And", and Kappa1 Sculptoris (no Flamsteed number) has "Kap1Scl".
7. ra, dec: The star's right ascension and declination, for epoch and equinox 2000.0.
8. proper: A common name for the star, such as "Barnard's Star" or "Sirius". These are taken from the International Astronomical Union (https://www.iau.org/public/themes/naming_stars/, specifically, I'm using a formatted version from https://github.com/mirandadam/iau-starnames)
9. dist: The star's distance in parsecs, the most common unit in astrometry. To convert parsecs to light years, multiply by 3.262. A value >= 100000 indicates missing or dubious (e.g., negative) parallax data in Hipparcos.
10. pmra, pmdec: The star's proper motion in right ascension and declination, in milliarcseconds per year.
11. rv: The star's radial velocity in km/sec, where known.
12. mag: The star's apparent visual magnitude.
13. absmag: The star's absolute visual magnitude (its apparent magnitude from a distance of 10 parsecs).
14. spect: The star's spectral type, if known.
15. ci: The star's color index (blue magnitude - visual magnitude), where known.
16. x,y,z: The Cartesian coordinates of the star, in a system based on the equatorial coordinates as seen from Earth. +X is in the direction of the vernal equinox (at epoch 2000), +Z towards the north celestial pole, and +Y in the direction of R.A. 6 hours, declination 0 degrees.
17. vx,vy,vz: The Cartesian velocity components of the star, in the same coordinate system described immediately above. They are determined from the proper motion and the radial velocity (when known). The velocity unit is parsecs per year; these are small values (around 1 millionth of a parsec per year), but they enormously simplify calculations using parsecs as base units for celestial mapping.
18. rarad, decrad, pmrarad, pmdecrad: The positions in radians, and proper motions in radians per year.
19. bayer: The Bayer designation as a distinct value
20. flam: The Flamsteed number as a distinct value
21. con: The standard constellation abbreviation
22. comp, comp_primary, base: Identifies a star in a multiple star system. comp = ID of companion star, comp_primary = ID of primary star for this component, and base = catalog ID or name for this multi-star system. Currently only used for Gliese stars.
23. lum: Star's luminosity as a multiple of Solar luminosity.
24. var: Star's standard variable star designation, when known.
25. var_min, var_max: Star's approximate magnitude range, for variables. This value is based on the Hp magnitudes for the range in the original Hipparcos catalog, adjusted to the V magnitude scale to match the "mag" field.

Additional Information

Details about previous versions (through HYG 4.1) are in version-info.md.

For additional background details, and older versions of the database, visit http://www.astronexus.com/hyg.

For the most current version of the applications using this database, visit https://endeavour.astronexus.com.