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Algol

This article is about the star. For the programming languages, see ALGOL. For other uses, see Algol (disambiguation).

Algol
Location of β Persei (circled)
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)34.7 ± 0.6 mas[7]
Distance94 ± 2 ly
(28.8 ± 0.5 pc)[7]
β Per Aa1
Absolute magnitude (MV)−0.07[8]
β Per Aa2
Absolute magnitude (MV)2.9[8]
β Per Ab
Absolute magnitude (MV)2.3[8]
Orbit[9]
Primaryβ Per Aa1
Companionβ 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[9]
Primaryβ Per A
Companionβ 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
Mass3.17 ± 0.21[9] M☉
Radius2.73 ± 0.20[9] R☉
Luminosity182[8] L☉
Surface gravity (log g)4.0[10] cgs
Temperature13,000[10] K
Rotational velocity (v sin i)49[11] km/s
Age570[8] Myr
β Per Aa2
Mass0.70±0.08[9] M☉
Radius3.48±0.28[9] R☉
Luminosity6.92[8] L☉
Surface gravity (log g)3.5[10] cgs
Temperature4,500[10] K
β Per Ab
Mass1.76±0.15[9] M☉
Radius1.73±0.33[9] R☉
Luminosity10.0[8] L☉
Surface gravity (log g)4.5[10] cgs
Temperature7,500[10] 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
SIMBADdata

Algol /ˈælɡɒl/,[12] 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. Based upon parallax measurements, Algol is located 94 light-years (29 parsecs) from Earth.[7]

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.[13]

Algol gives its name to its class of eclipsing variable, known as Algol variables.

  1. ^ a b c d 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.
  2. ^ 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.
  3. ^ 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.
  4. ^ a b Cite error: The named reference lestrade1993 was invoked but never defined (see the help page).
  5. ^ Cite error: The named reference frank2022 was invoked but never defined (see the help page).
  6. ^ Fletcher, Emery S. (1964). "Spectrophotometry of Algol". The Astronomical Journal. 69: 357. Bibcode:1964AJ.....69..357F. doi:10.1086/109284.
  7. ^ a b c Xu, Shuangjing; Zhang, Bo; Reid, Mark J.; Zheng, Xingwu; Wang, Guangli (2019-04-20). "Comparison of Gaia DR2 Parallaxes of Stars with VLBI Astrometry". The Astrophysical Journal. 875 (2): 114. arXiv:1903.04105. Bibcode:2019ApJ...875..114X. doi:10.3847/1538-4357/ab0e83. ISSN 0004-637X.
  8. ^ 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.
  9. ^ 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.
  10. ^ 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.
  11. ^ 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.
  12. ^ "Algol". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.)
  13. ^ "Beta Persei (Algol)". AAVSO. January 1999. Archived from the original on 8 July 2006. Retrieved 31 July 2006.

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