Global InformationAlgol information
  | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Perseus |
| Right ascension | 03h 08m 10.13245s[1] |
| Declination | +40° 57′ 20.3280″[1] |
| Apparent magnitude (V) | 2.12[2] (- 3.39[3]) |
| Characteristics | |
| Spectral type | Aa1: B8V[4] Aa2: K0IV[4] Ab: F1V[5] (kA4hA9.5mF0:[6]) |
| U−B colour index | −0.37[2] |
| B−V colour index | −0.05[2] |
| Variable type | EA/SD[3] |
| Astrometry | |
| Radial velocity (Rv) | 3.7 km/s |
| Proper motion (μ) | RA: 2.99[1] mas/yr Dec.: −1.66[1] mas/yr |
| Parallax (π) | 36.27 ± 1.40 mas[1] |
| Distance | 90 ± 3 ly (28 ± 1 pc) |
| β Per Aa1 | |
| Absolute magnitude (MV) | −0.07[7] |
| β Per Aa2 | |
| Absolute magnitude (MV) | 2.9[7] |
| β Per Ab | |
| Absolute magnitude (MV) | 2.3[7] |
| Orbit[8] | |
| Primary | β Per Aa1 |
| Companion | β Per Aa2 |
| Period (P) | 2.867328 days |
| Semi-major axis (a) | 0.00215″ |
| Eccentricity (e) | 0 |
| Inclination (i) | 98.70° |
| Longitude of the node (Ω) | 43.43° |
| Orbit[8] | |
| Primary | β Per A |
| Companion | β Per B |
| Period (P) | 680.168 days |
| Semi-major axis (a) | 0.09343″ |
| Eccentricity (e) | 0.227 |
| Inclination (i) | 83.66° |
| Longitude of the node (Ω) | 132.66° |
| Periastron epoch (T) | 2446927.22 |
| Argument of periastron (ω) (primary) | 310.02° |
| Details | |
| β Per Aa1 | |
| Mass | 3.17 ± 0.21[8] M☉ |
| Radius | 2.73 ± 0.20[8] R☉ |
| Luminosity | 182[7] L☉ |
| Surface gravity (log g) | 4.0[9] cgs |
| Temperature | 13,000[9] K |
| Rotational velocity (v sin i) | 49[10] km/s |
| Age | 570[7] Myr |
| β Per Aa2 | |
| Mass | 0.70±0.08[8] M☉ |
| Radius | 3.48±0.28[8] R☉ |
| Luminosity | 6.92[7] L☉ |
| Surface gravity (log g) | 3.5[9] cgs |
| Temperature | 4,500[9] K |
| β Per Ab | |
| Mass | 1.76±0.15[8] M☉ |
| Radius | 1.73±0.33[8] R☉ |
| Luminosity | 10.0[7] L☉ |
| Surface gravity (log g) | 4.5[9] cgs |
| Temperature | 7,500[9] K |
| Other designations | |
Algol, Gorgona, Gorgonea Prima, Demon Star, El Ghoul, β Persei, β Per, 26 Persei, BD+40°673, FK5 111, GC 3733, HD 19356, HIP 14576, HR 936, PPM 45864, SAO 38592. | |
| Database references | |
| SIMBAD | data |
Algol /ˈælɡɒl/,[11] designated Beta Persei (β Persei, abbreviated Beta Per, β Per), known colloquially as the Demon Star, is a bright multiple star in the constellation of Perseus and one of the first non-nova variable stars to be discovered.
Algol is a three-star system, consisting of Beta Persei Aa1, Aa2, and Ab – in which the hot luminous primary β Persei Aa1 and the larger, but cooler and fainter, β Persei Aa2 regularly pass in front of each other, causing eclipses. Thus Algol's magnitude is usually near-constant at 2.1, but regularly dips to 3.4 every 2.86 days during the roughly 10-hour-long partial eclipses. The secondary eclipse when the brighter primary star occults the fainter secondary is very shallow and can only be detected photoelectrically.[12]
Algol gives its name to its class of eclipsing variable, known as Algol variables.
- ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
- ^ a b c Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
- ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007–2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1: 02025. Bibcode:2009yCat....102025S.
- ^ a b Cite error: The named reference
lestrade1993was invoked but never defined (see the help page). - ^ Cite error: The named reference
frank2022was invoked but never defined (see the help page). - ^ Fletcher, Emery S. (1964). "Spectrophotometry of Algol". The Astronomical Journal. 69: 357. Bibcode:1964AJ.....69..357F. doi:10.1086/109284.
- ^ a b c d e f g Soderhjelm, S. (1980). "Geometry and dynamics of the Algol system". Astronomy and Astrophysics. 89 (1–2): 100. Bibcode:1980A&A....89..100S.
- ^ a b c d e f g h Baron, F.; Monnier, J. D.; Pedretti, E.; Zhao, M.; Schaefer, G.; Parks, R.; Che, X.; Thureau, N.; Ten Brummelaar, T. A.; McAlister, H. A.; Ridgway, S. T.; Farrington, C.; Sturmann, J.; Sturmann, L.; Turner, N. (2012). "Imaging the Algol Triple System in the H Band with the CHARA Interferometer". The Astrophysical Journal. 752 (1): 20. arXiv:1205.0754. Bibcode:2012ApJ...752...20B. doi:10.1088/0004-637X/752/1/20. S2CID 11110989.
- ^ a b c d e f Zavala, R. T.; Hummel, C. A.; Boboltz, D. A.; Ojha, R.; Shaffer, D. B.; Tycner, C.; Richards, M. T.; Hutter, D. J. (2010). "The Algol Triple System Spatially Resolved at Optical Wavelengths". The Astrophysical Journal Letters. 715 (1): L44–L48. arXiv:1005.0626. Bibcode:2010ApJ...715L..44Z. doi:10.1088/2041-8205/715/1/L44. S2CID 118573026.
- ^ Tomkin, J.; Huisong, T. (1985). "The rotation of the primary of Algol". Publications of the Astronomical Society of the Pacific. 97: 51. Bibcode:1985PASP...97...51T. doi:10.1086/131493. S2CID 119392903.
- ^ "Algol". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
- ^ "Beta Persei (Algol)". AAVSO. January 1999. Archived from the original on 8 July 2006. Retrieved 31 July 2006.