juliensimon/wds-double-stars

Washington Double Star Catalog

Credit: NASA/ESA/Hubble

Part of a dataset collection on Hugging Face.

Dataset description

The Washington Double Star Catalog (WDS) is the world reference catalog for visual double and multiple star systems, maintained by the US Naval Observatory.

Double stars are essential for determining stellar masses -- the most fundamental property of a star -- and for testing stellar evolution models. The WDS traces its lineage back to Sherburne Wesley Burnham's catalog of 1906 and has been continuously maintained at the US Naval Observatory for over a century, incorporating astrometric measurements from visual micrometry, speckle interferometry, adaptive optics, long-baseline optical interferometry, and space-based observations (Hipparcos, Gaia).

The catalog includes both gravitationally bound physical pairs (true binaries) and optical doubles -- chance alignments of unrelated stars along the same line of sight. Distinguishing between the two requires common proper motion analysis or, ideally, measurement of orbital curvature over a sufficient arc of the orbit.

For physical binaries with well-determined orbits, the combination of angular separation, orbital period, and parallax yields dynamical masses through Kepler's third law. These direct mass measurements are the gold standard for calibrating the mass-luminosity relation and testing stellar structure models across spectral types from O-type supergiants to late M-dwarfs. The position angle and separation measurements recorded at the first and last epochs encode information about orbital motion: systems showing significant changes in these quantities over the observing baseline are strong candidates for orbit determination.

The WDS encompasses an enormous diversity of systems, from pairs separated by fractions of an arcsecond -- resolvable only by interferometric techniques -- to wide common proper motion companions separated by arcminutes or more. Wide binaries (separations > 1000 AU) are particularly interesting as probes of the Galactic gravitational potential.

This dataset is suitable for tabular classification, tabular regression tasks.

Schema

Column	Type	Description	Sample	Null %
wds_id	str	WDS designation in format 'HHMMM+DDMMM' encoding the J2000 position (e.g. '00055+5258'); the standard identifier for double stars in this catalog	00000+0044	0.0%
discoverer_code	str	Standard WDS discoverer code + sequence number (e.g. 'STF2272' = Struve discovery #2272); identifies the original survey or observer	SKF1115	0.0%
components	str	Component pair designation (e.g. 'AB' = primary+secondary, 'AC' = primary+tertiary); systems may have multiple entries for different pairs	AB	73.0%
first_observation_year	int64	Year of the earliest published observation of this pair (fractional year, e.g. 1889.0)	2001	0.0%
last_observation_year	int64	Year of the most recent published observation (fractional year); span indicates how long the pair has been monitored	2015	0.0%
n_observations	int64	Total number of published position-angle/separation measurements for this pair	3	0.0%
position_angle_first	int64	Position angle of secondary relative to primary at epoch of first observation (degrees, 0-359, measured East from North); change over time may reveal orbital motion	33	0.0%
position_angle_last	int64	Position angle at epoch of last observation (degrees, 0-359); compare with position_angle_first to detect orbital motion	30	0.0%
separation_first_arcsec	float64	Angular separation between primary and secondary at first observation (arcseconds); decreasing separation may indicate an inclined orbit	0.8	0.0%
separation_last_arcsec	float64	Angular separation at last observation (arcseconds); null if only one observation exists	1.0	0.0%
magnitude_primary	float64	Visual (V-band) magnitude of the primary star; null if not measured	17.8	0.1%
magnitude_secondary	float64	Visual (V-band) magnitude of the secondary star; null if not measured; difference = magnitude contrast	17.8	1.1%
spectral_type	str	MK spectral type of the primary component (e.g. 'G2V', 'K0III'); null if not cataloged	M1	53.1%
ra_deg	float64	Right ascension of the primary star, ICRS J2000.0 (degrees, 0-360)	359.999375	0.0%
dec_deg	float64	Declination of the primary star, ICRS J2000.0 (degrees, -90 to +90)	0.7257499999999999	0.0%

Quick stats

• 157,371 double/multiple star systems
• Observations spanning -1 to 2025
• 157,371 with measured separation
• 73,828 with spectral type

Usage

from datasets import load_dataset

ds = load_dataset("juliensimon/wds-double-stars", split="train")
df = ds.to_pandas()

from datasets import load_dataset

ds = load_dataset("juliensimon/wds-double-stars", split="train")
df = ds.to_pandas()

# Systems with large separation change (orbital motion)
has_both = df.dropna(subset=["separation_first_arcsec", "separation_last_arcsec"])
has_both["sep_change"] = abs(has_both["separation_last_arcsec"] - has_both["separation_first_arcsec"])
movers = has_both.nlargest(20, "sep_change")
print(movers[["wds_id", "separation_first_arcsec", "separation_last_arcsec", "sep_change"]])

# Separation distribution
import matplotlib.pyplot as plt
df["separation_last_arcsec"].dropna().clip(upper=100).hist(bins=100)
plt.xlabel("Separation (arcsec)")
plt.ylabel("Count")
plt.title("WDS Angular Separation Distribution")
plt.show()

Data source

https://vizier.cds.unistra.fr/viz-bin/VizieR-3?-source=B/wds/wds

Related datasets

• juliensimon/hipparcos-catalog

• juliensimon/gcvs-variable-stars

• juliensimon/open-star-clusters

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About the author

Created by Julien Simon — AI Operating Partner at Fortino Capital. Part of the Space Datasets collection.

Citation

@dataset{wds_double_stars,
  title = {Washington Double Star Catalog},
  author = {juliensimon},
  year = {2026},
  url = {https://huggingface.co/datasets/juliensimon/wds-double-stars},
  publisher = {Hugging Face}
}

License

CC-BY-4.0