Albireo
Albireo /ælˈbɪrioʊ/ is a double star designated Beta Cygni (β Cygni, abbreviated Beta Cyg, β Cyg). The International Astronomical Union uses the name "Albireo" specifically for the brightest star in the system. Although designated 'beta', it is fainter than Gamma Cygni, Delta Cygni, and Epsilon Cygni and is the fifth-brightest point of light in the constellation of Cygnus. Appearing to the naked eye to be a single star of magnitude 3, viewing through even a low-magnification telescope resolves it into its two components. The brighter yellow star, itself a very close binary system, makes a striking colour contrast with its fainter blue companion.
| Observation data Epoch J2000.0 Equinox J2000.0 (ICRS) | |
|---|---|
| Constellation | Cygnus |
| Albireo Aa | |
| Right ascension | 19h 30m 43.286s |
| Declination | +27° 57′ 34.84″ |
| Apparent magnitude (V) | 3.21 |
| Albireo Ac | |
| Right ascension | 19h 30m 43.295s |
| Declination | +27° 57′ 34.62″ |
| Apparent magnitude (V) | 5.85 |
| Albireo B | |
| Right ascension | 19h 30m 45.3962s |
| Declination | +27° 57′ 54.989″ |
| Apparent magnitude (V) | 5.11 |
| Characteristics | |
| Albireo Aa | |
| Spectral type | K2II |
| B−V color index | +1.13 |
| V−R color index | +0.92 |
| Albireo Ac | |
| Spectral type | B8:p |
| B−V color index | +0.09 |
| V−R color index | +0.09 |
| Albireo B | |
| Spectral type | B8Ve |
| U−B color index | -0.32 |
| B−V color index | -0.10 |
| Astrometry | |
| Radial velocity (Rv) | −23.54 km/s |
| Proper motion (μ) | RA: −7.17 mas/yr Dec.: −6.15 mas/yr |
| Parallax (π) | 7.51 ± 0.33 mas |
| Distance | 430 ± 20 ly (133 ± 6 pc) |
| Albireo Aa | |
| Absolute magnitude (MV) | −2.45 |
| Albireo Ac | |
| Absolute magnitude (MV) | −0.25 |
| Albireo B | |
| Radial velocity (Rv) | −18.80 km/s |
| Proper motion (μ) | RA: −1.078 mas/yr Dec.: −1.540 mas/yr |
| Parallax (π) | 8.16 ± 0.25 mas |
| Distance | 400 ± 10 ly (123 ± 4 pc) |
| Position (relative to Albireo A) | |
| Component | Albireo B |
| Epoch of observation | 2006 |
| Angular distance | 35.3″ |
| Position angle | 54° |
| Orbit | |
| Primary | Aa |
| Companion | Ac |
| Period (P) | 121.65+3.34 −2.90 yr |
| Semi-major axis (a) | 0.401+0.007 −0.006″ |
| Eccentricity (e) | 0.20+0.01 −0.02 |
| Inclination (i) | 156.15+2.90 −2.63° |
| Longitude of the node (Ω) | 84.43+5.27 −4.50° |
| Periastron epoch (T) | B2026.36 |
| Argument of periastron (ω) (secondary) | 54.72+1.88 −2.24° |
| Semi-amplitude (K1) (primary) | 2.91+0.09 −0.12 km/s |
| Details | |
| Albireo Aa | |
| Mass | 5.2 M☉ |
| Radius | 62 R☉ |
| Luminosity (bolometric) | 1,259 L☉ |
| Surface gravity (log g) | 0.93 cgs |
| Temperature | 4,383 K |
| Metallicity [Fe/H] | −0.1 dex |
| Rotational velocity (v sin i) | 8.34 km/s |
| Albireo Ac | |
| Mass | 2.7 M☉ |
| Radius | 3.0 R☉ |
| Luminosity (bolometric) | 79 L☉ |
| Temperature | 10,000 K |
| Albireo B | |
| Mass | 3.7 ± 0.8 M☉ |
| Radius | 2.59 R☉ |
| Luminosity (bolometric) | 230 ± 90 L☉ |
| Surface gravity (log g) | 4.00 ± 0.15 cgs |
| Temperature | 13,200 ± 600 K |
| Age | 100 Myr |
| Other designations | |
| Albireo A: β¹ Cygni, BD+27 3410, HR 7417, HD 183912/183913, HIP 95947, SAO 87301, FK5 732, MCA 55 Aac, NSV 12105 | |
| Albireo B: β² Cygni, STF 4043B, BD+27 3411, HD 183914, HIP 95951, HR 7418, SAO 87302 | |
| Database references | |
| SIMBAD | β Cyg (STF 4043) |
| Albireo A | |
| Albireo Aa | |
| Albireo Ab | |
| Albireo B | |
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