The object was found in the following catalogues:
  1. The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version)

  2. SKY2000 - Master Star Catalog

  3. Smithsonian Astrophysical Observatory Star Catalog

  4. The Washington Visual Double Star Catalog, 1996.0

  5. 4th Catalog of Orbits of Visual Binaries

  6. Combined General Catalogue of Variable Stars (Vol. I-III)

catalogues and names Algol, b Per, bet Per, 26 Per, HR 936, HD 19356, SAO 38592, FK5: 111, WDS 03082+4057A
other names Gorgona, Gorgonea Prima, Demon Star, El Ghoul
constellation Perseus

data from The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version) (Hoffleit+, 1991)

note (category: star names): ALGOL; Gorgona; Gorgonea Prima; Demon Star; El Ghoul.

object is infrared source (NASA merged infrared catalogue, Schmitz et al., 1978)

position, motion, parallax:

position (J2000) RA: 3h 8min 10,1sec DEC: +40 57' 20''
position (J1900) RA: 3h 1min 39,5sec DEC: +40 34' 14''
proper motion (J2000) RA: 0,004 arcsec/a DEC: -0,001 arcsec/a
radial velocity 4 km/s
note: spectroscopic binaries
note: orbital data avaible
rotational velocity 65 km/s (uncertain) (variable)
trigonometric parallax 0,045 arcsec


visual magnitude 2,12
(V on UBV Johnson system)

spectral / color information

spectral class B8V
B-V-magnitude -0,05
U-B-magnitude -0,37
R-I-magnitude -0,03
note (category: spectra): B8V+G.
note (category: colors): Color excess E(B-V) = +0.03.

variability information

variable star identification Bet Per
note (category: variability): ADS 2362A is the prototype Algol star, first discovered as variable by Montanari in 1669. The first period determined by Goodricke in 1783, who also interpreted the variations as due to eclipses. The prototype star proves to be a more a complicated system than most of the Algol-type stars, i.e., compact triple system with separation of the components well under 0.1". The components usually designated Algol A, B, C, sometimes A, a, P. Two formerly additionally desig- nated components D and E, inferred on the basis of an apparent 32 year apsidal motion, are now considered spurious. The various Algol components must not be confused with the visual components ADS 2362 B-E, optical companions at much greater distances from A. ADS 2362A, EA 2.12 - 3.40V, 2.86732442d, abrupt period changes. Orbital and rotation periods synchronized. Rotational velocity 65k/s. Radio flares extending to about 1 A.U., not associated with X-ray activity. Radio flare activity appears correlated with period discontinuities, attributed to "starquakes." Mass flow from K to B8 component at rate of 1.8x10E-08 solar masses/year. Possible circumstellar material associated with radio or H alpha emission.

double/multiple star system information

number of components of multiple star system 6
separation 81,9 arcsec
mag difference (of double or brightest multiple) 8,3
component ID AD
note (category: double and multiple data): A* var. B8V, 1.858y, a = 0.011" or 1.862y, a = 0.104". Apparent apsidal period 28.4y or 32y. Resolved by speckle interferometry: sep. 0.086", 2-3v fainter than primary. This may be Algol C. Four visual companions all optical: B, 12.7v at 59"; C, 12.5 at 67"; D, 10.5 at 82"; BC sep. 15"; E, 12.5v at 11" from D.
note (category: spectroscopic binaries): Algol ABxC: 1.8613y, K 12.0k/s, V0 +3.7k/s, msin3i 3.91, asini 109. Spectra B8V, G5IV, Am. Mass Algol AB, 5.3 Suns; C, 1.8 Suns. Circumstellar gas fills Roche lobe of hot component. ADS 19356A: 2.8673d, K 44.0k/s, V0 var., asini 1.73. Resolved by speckle interferometry 1982.17, sep. 0.052", 1983.94, sep. 0.08".

miscellaneous information

note (category: miscellaneous): One of the few known galactic radio sources in which the dominant star is normal. 21cm radio source.

data from SKY2000 - Master Star Catalog (Myers+ 1997)

position, motion, parallax:

position (J2000) RA: 3h 8min 10,128sec DEC: +40 57' 20,25'' 0,01 arcsec source: 40
proper motion (J2000) RA: -0,0001 arcsec/a DEC: 0,001 arcsec/a source: 40
radial velocity 4 km/s source: 25
trigonometric parallax 0,034 0,001 arcsec source: 40
galactic coord. (B1950) longitude: 148,98 latitude: -14,9
GCI unit vector (J2000) X: 0,51465 Y: 0,55271 Z: 0,655474


visual 2,094 (observed) source: 31

spectral information:

spectral class B8 source: 96
Morgan-Keenan B8V source: 25
B-magnitude 2,07 0,05 B-V-magnitude -0,05
U-magnitude 1,7 0,05 U-B-magnitude -0,37

variability information:

source of data: 30
variability type 10
var. amplitude 1,27
var. period 2,87
var. epoch 2445642
3. November 1983, 12:00:00 UT
next max light 2451623,08
19. March 2000, 13:55:12 UT

double/multiple star system information:

source of data: 19
separation between brightest and second brightest component 58,8 arcsec
position angle 155


19 WDS Catalog
Worley, C.E., and G.G. Douglass, Washington Catalog of Visual Double Stars 1996.0, United States Naval Observatory, 1996
25 Bright Star Catalogue, 5th edition
Hoffleit, D. and Warren, W.H. Jr., The Bright Star Catalogue, 5th Revised Edition, Version 2, 1994
30 GCVS, 4th edition
Kholopov, P.N., et al., General Catalogue of Variable Stars, fourth edition, Moscow: Nauka Publishing House, 1985-88
31 CRM' (non-GCVS variable data)
Warren, W.H. Jr., Northern Hemisphere Catalog of Red Magnitudes, 1994
40 Astrometric Studies
Gatewood, G., de Jonge, J.K. and Heintz, W.D., 1995, A.J. 109, 434, "Astrometric Studies in the Region of Algol"
96 SAO or HD/HDE Catalog
Reference from Value 1 or Reference from Value 2

data from Smithsonian Astrophysical Observatory Star Catalog (SAO Staff 1966; USNO, ADC 1990)

position and proper motion:

position (J1950) RA: 3h 4min 54,356sec DEC: +40 45' 52,46'' 0,004 arcsec
position (J2000) RA: 3h 8min 10,131sec DEC: +40 57' 20,44''
proper motion J1950 (FK4) RA: 0,0003 arcsec/a DEC: 0,002 arcsec/a 0,001 arcsec/a in RA
0,001 arcsec/a in DEC
proper motion J2000 (FK5) RA: 0,0003 arcsec/a DEC: -0,001 arcsec/a
source of proper motion data Determined by source catalog


visual 2,9 (accuracy: 2 decimals)
source of visual magnitude data Arithmetic mean of maximum and minimum magnitudes of a variable star

spectral information:

spectral class B8
source of spectral data Taken from the Henry Draper Catalogue or no spectrum in source catalog.

remarks for duplicity and variability

Variable star in visual magnitude in source catalog


source catalogue FK4, catalogue number: 111
Durchmusterung BD+40 673
Boss General Catalogue 3733
Henry Draper Catalogue 19356

data from The Washington Visual Double Star Catalog, 1996.0 (Worley+, 1996)

position and proper motion:

position (J2000) RA: 3h 8,2min DEC: +40 57'
proper motion (J2000) RA: 0,004 arcsec/a DEC: -0,001 arcsec/a

double/multiple star system information:

component year number of measures position angle angular separation magnitude of 1st component magnitude of 2nd component spectral class(es) discoverer code
Aa 1973 18 130 0,1'' 2,12 - B8V LAB
AB 1878 8 155 58,8'' - 12,7 B8V BU 526
AC 1878 8 145 67,5'' - 12,5 - BU 526
AD 1879 11 192 81,9'' - 10,5 - BU 526
AE 1899 1 185 85,7'' - - B8V BU 526
BC 1891 2 102 14,8'' - - - BU 526
1899 - 13,9''
DE 1878 6 115 10,8'' 10,5 12,5 - BU 526
1922 118 11,4''

discoverer information:

discoverer code discoverer reference
LAB Labeyrie et al
BU 526 Burnham, S.W. -


note Beta Per. Algol, prototype of the Algol-type binaries. Also, a spectroscopic binary with P = 1.86 yr.

data from 4th Catalog of Orbits of Visual Binaries (Worley+, 1983)


position (J1900) RA: 3h 1,7min DEC: +40 34'

magnitudes, spectral classes, orbital elements:

author: P.J. Bachmann, J.L. Hershey A. Labeyrie et al
date of observation: 1973
spectral class component B: B8V B8V
spectral class component B: B8V B8V
period [y]: 1,858 1,862
semi-major axis [arcsec]: 0,011 0,104
inclination [deg]: 61,1 83
node [deg]: 106 (ascending) 131 (ascending)
eccentricity: 0,2 0,23
time of periastron passage: 1903,6 1952,05
dates of ephemeris: 1975-1976
grade: reliable
reference: Astron. J. 80, 836, 1975. Astrophys. J. 194, L147; 1974.
notes Algol, the well-known eclipsing binary, a radio and X-ray source, is triple (and possibly quadruple, but the variation with the 32 yr period is more probably an apsidal rotation of the eclipsing pair). The third star, with the spectroscopically determined 1.8 yr period has been resolved by speckle interferometry; the magnitude difference is about 2.5. The first orbit listed is astrometric,the second from the speckle data. The spectroscopic data were discussed by G. Hill et al (Astrophys. J. 162, 265; 1970 and 168, 443; 1971). ADS lists several distant, faint, and probably optical companions.