Albireo (Beta Cygni A & B)
Coordinates, Gaia DR3 parallaxes of Beta Cygni A & B, 34.6″ angular separation, color contrast, and observing guide for Albireo in Cygnus.
Provenance-Backed Scientific Measurements
Every measurement below preserves its unit, uncertainty interval, observational method, reference epoch, quality status, and primary catalog source. See Uncertainty & Provenance for how competing measurements are handled.
| Parameter | Value | Uncertainty | Method & Epoch | Quality Status | Source Archive |
|---|---|---|---|---|---|
| Apparent magnitude (Albireo A) | 3.08 mag | ± 0.02 mag | Johnson UBV photometry (Albireo B = 5.11 mag) | definitive | Hipparcos New Reduction Catalog |
| Visual A–B angular separation | 0.577 arcmin | ± 0.002 arcmin | Washington Double Star Catalog astrometry (34.6 arcseconds at PA 54°) | definitive | SIMBAD Astronomical Database (CDS) |
| Distance to Albireo B (Gaia DR3) | 119.4 pc | ± 2.2 pc | Gaia DR3 parallax of β² Cygni (8.37 ± 0.15 mas) (J2016.0) | definitive | ESA Gaia Archive — Data Release 3 |
| Effective temperature (Albireo Aa vs B) | 4270 K | ± 60 K | K3 II giant spectroscopy (Albireo B = 13,200 ± 300 K) | definitive | SIMBAD Astronomical Database (CDS) |
J2000 Equatorial Sky Chart & Culmination Altitude
The chart below plots Albireo (Beta Cygni Color Double Star) at RA 19h 30m 43.29s, Dec +27° 57′ 34.8″ within Cygnus, alongside peak meridian transit altitudes for 40°N and 30°S observers. Use the RA/Dec Coordinate Converter to compute exact culmination altitude for your latitude.
Astrophysical Context & Structure
Albireo (Beta Cygni), marking the beak of Cygnus the Swan at the center of the Summer Triangle, is the most famous color-contrast double star in the night sky. Separated by a generous 34.6 arcseconds along position angle 54°, the pair consists of magnitude 3.08 Albireo A (β¹ Cygni, a 4,270 K K3 II bright giant glowing rich topaz-gold) and magnitude 5.11 Albireo B (β² Cygni, a 13,200 K B8 Ve main-sequence star shining sapphire blue-green).
For decades textbooks assumed Albireo A and B were a physically bound binary with an orbital period of ~100,000 years. However, high-precision Gaia DR3 astrometry shows that Albireo B lies at 119.4 ± 2.2 parsecs (389 light-years) and moves with a very different proper motion from Albireo A—meaning the two stars are either an unbound line-of-sight optical double within the same Cygnus star-forming stream or a disrupted system where internal orbital recoil masks their common motion.
Speckle interferometry and adaptive optics further reveal that golden Albireo A is itself a close hierarchical triple system: the K3 II giant (Aa) is orbited at 0.4 arcseconds (~50 AU, period ~214 years) by a hot B9.5 V star (Albireo Ac), plus a faint third companion.
Practical Visual Observing Guide
- Situated at the southwestern foot of the Northern Cross in Cygnus, midway between Vega and Altair.
- At 34.6 arcseconds separation, steadily braced 10×50 or 15×70 binoculars can split Albireo, while any 50–100 mm telescope at 25×–60× displays the striking gold-and-sapphire color contrast.
- Slightly defocusing the stars at low power saturates the warm orange-gold of the K3 giant and the vivid blue of the B8 dwarf on your retina's color cones.
Catalog Cross-Identifications & Aliases
Common Aliases: β Cygni · HD 183912 / HD 183914 · HIP 95947
| Catalog Authority | Identifier |
|---|---|
| HIP | HIP 95947 |
| HD | HD 183912 |
| SIMBAD | * bet Cyg |
| WIKIDATA | Q13032 |
Related Objects, Comparisons & Guides
Epsilon Lyrae (The Double Double Star)
Coordinates, Gaia DR3 distance (160 ly), 208″ wide pair and 2.3″/2.4″ tight sub-pairs, and telescope resolution test guide for Epsilon Lyrae.
Mizar & Alcor (Zeta Ursae Majoris System)
Coordinates, Hipparcos/VLBI distance (82.8 ly), 11.8′ naked-eye pair, 14.4″ Mizar A–B split, and observing guide for Mizar & Alcor.
Dumbbell Nebula (Messier 27 in Vulpecula)
Coordinates, Gaia DR3 distance (389 pc), magnitude 7.4, central white dwarf, and observing guide for the Dumbbell Nebula (M27).
Veil Nebula (Cygnus Loop NGC 6960/6992)
Coordinates, Gaia distance (735 pc), O-III filament structure, and visual filter guide for the Veil Nebula supernova remnant in Cygnus.
Splitting Bright Double & Multiple Stars Guide
How to resolve showcase binary and multiple star systems—Albireo, Mizar & Alcor, Epsilon Lyrae, Castor, and Sirius B—and test telescope Dawes limit.
Northern Summer Milky Way Observing Tour
Summer observing guide from the Summer Triangle (Vega, Altair, Deneb) and Hercules Keystone down the Milky Way rift to the Sagittarius Galactic Center.
Stellar Spectral Classification (OBAFGKM)
Reference guide to Morgan-Keenan (MK) stellar classification (O B A F G K M), luminosity classes (I–V, WD), color index (B-V), and the H-R diagram.
Angular Size, Separation & Field of View
How angular diameter (degrees, arcminutes, arcseconds), spherical angular separation, and small-angle physical diameter relate to telescope field of view.
Scientific Sources & Dataset Provenance
- ESA Gaia Archive — Data Release 3 (DR3 (2022-06-13)): Gaia Collaboration, Vallenari, A., et al. 2023, A&A, 674, A1 (Gaia Data Release 3) — European Space Agency / Gaia DPAC
- Hipparcos New Reduction Catalog (2007 New Reduction): van Leeuwen, F. 2007, A&A, 474, 653 (Validation of the new Hipparcos reduction) — ESA / van Leeuwen (2007)
- IAU Working Group on Star Names (WGSN) (2026 IAU WGSN Bulletin): Mamajek, E., et al. (IAU WGSN) 2016–2026, IAU Catalog of Star Names — International Astronomical Union