Algol
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] | |
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] | |
Longitude of the node (Ω) | 43.43° | |
Argument of periastron (ω)(primary) | 310.02° | |
Details | ||
β Per Aa1 | ||
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 | |
38592. | ||
Database references | ||
SIMBAD | data |
Algol to be discovered.
Algol is a
Algol gives its name to its class of eclipsing variable, known as Algol variables.
Observation history
An ancient Egyptian calendar of lucky and unlucky days composed some 3,200 years ago is said to be the oldest historical documentation of the discovery of Algol.[13][14] [15]
The association of Algol with a demon-like creature (
The variability of Algol was noted in 1667 by Italian astronomer Geminiano Montanari,[19] but the periodic nature of its variations in brightness was not recognized until more than a century later, when the British amateur astronomer John Goodricke also proposed a mechanism for the star's variability.[20][21] In May 1783, he presented his findings to the Royal Society, suggesting that the periodic variability was caused by a dark body passing in front of the star (or else that the star itself has a darker region that is periodically turned toward the Earth). For his report he was awarded the Copley Medal.[22]
In 1881, the Harvard astronomer
System
Algol is a multiple-star system with three confirmed and two suspected stellar components.
The three components of the bright triple star used to be, and still sometimes are, referred to as β Per A, B, and C. The
The close pair consists of a B8 main sequence star and a much less massive K0 subgiant, which is highly distorted by the more massive star. These two orbit every 2.9 days and undergo the eclipses that cause Algol to vary in brightness. The third star orbits these two every 680 days and is an A or F-type main sequence star. It has been classified as an Am star, but this is now considered doubtful.[5][29]
Studies of Algol led to the
This system also exhibits x-ray and radio wave[33] flares. The x-ray flares are thought to be caused by the magnetic fields of the A and B components interacting with the mass transfer.[34] The radio-wave flares might be created by magnetic cycles similar to those of sunspots, but because the magnetic fields of these stars are up to ten times stronger than the field of the Sun, these radio flares are more powerful and more persistent.[35][36] The secondary component was identified as the radio emitting source in Algol using Very-long-baseline interferometry by Lestrade and co-authors.[4]
Magnetic activity cycles in the chromospherically active secondary component induce changes in its radius of gyration that have been linked to recurrent orbital period variations on the order of ΔP/P ≈ 10−5 via the Applegate mechanism.[37] Mass transfer between the components is small in the Algol system[38] but could be a significant source of period change in other Algol-type binaries.
Algol is about 92.8 light-years from the Sun, but about 7.3 million years ago it passed within 9.8 light-years of the Solar System[39] and its apparent magnitude was about −2.5, which is considerably brighter than the star Sirius is today. Because the total mass of the Algol system is about 5.8 solar masses, at the closest approach this might have given enough gravity to perturb the Oort cloud of the Solar System somewhat and hence increase the number of comets entering the inner Solar System. However, the actual increase in net cometary collisions is thought to have been quite small.[40]
Names
Beta Persei is the star's Bayer designation.
The official name Algol
The name Algol derives from
Ghost and demon star
Algol was called Rōsh ha Sāṭān or "Satan's Head" in Hebrew folklore, as stated by Edmund Chilmead, who called it "Divels head" or Rosch hassatan. A Latin name for Algol from the 16th century was Caput Larvae or "the Spectre's Head".[42] Hipparchus and Pliny made this a separate, though connected, constellation.[42]
First star of Medusa's head
Earlier the name of the constellation Perseus was Perseus and Medusa's Head where an asterism representing the head of Medusa after Perseus has cut it off already known in ancient Rome.
Chinese names
In
Cultural significance
The constellation Perseus and Algol, the Bright Star in the Gorgon's head | |
---|---|
Historically, the star has received a strong association with bloody violence across a wide variety of cultures. In the
See also
- Jaana Toivari-Viitala, egyptologist who contributed to understanding Ancient Egypt and the star
References
- ^ S2CID 18759600.
- ^ Bibcode:2002yCat.2237....0D.
- ^ Bibcode:2009yCat....102025S.
- ^ ISSN 0004-637X.
- ^ Bibcode:2022JAVSO..50..123F.
- doi:10.1086/109284.
- ^ Bibcode:1980A&A....89..100S.
- ^ S2CID 11110989.
- ^ S2CID 118573026.
- 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.
- S2CID 162969143.
- S2CID 119191453.
- PMID 26679699.
- Bibcode:1996JAVSO..24..129W.
- Bibcode:1957S&T....16..177D.
- ^ "Ian Ridpath's Star Tales – Perseus".
- ^ G. Montanari, "Sopra la sparizione d'alcune stelle et altre novità celesti", in: Prose de Signori Accademici Gelati di Bologna (Bologna: Manolessi, 1671), pp. 369–92 (Google books).
- ^ ADS O.J. Eggen,"An Eighteenth Century Discussion of Algol", The Observatory, 77 (1957), 191–197.
- .
- ^ "John Goodricke, The Discovery of the Occultating Variable Stars". 6 August 2003. Archived from the original on 22 June 2006. Retrieved 31 July 2006.
- Bibcode:1881AReg...19..253.
- S2CID 125814848.
- doi:10.1086/141796.
- ^ Meltzer, Alan S., A "Spectroscopic Investigation of Algol". Astrophysical Journal, vol. 125, (1957), p.359, BibCode:1957ApJ...125..359M
- S2CID 239882152.
- doi:10.1086/323920.
- .
- .
- ISSN 0004-637X.
- S2CID 118319759.
- S2CID 4222515.
- .
- ^ Blue, Charles E. (3 June 2002). "Binary Stars "Flare" With Predictable Cycles, Analysis of Radio Observations Reveals". National Radio Astronomy Observatory. Archived from the original on 2 July 2006. Retrieved 31 July 2006.
- ISSN 0067-0049.
- doi:10.1086/170967.
- Bibcode:2006PhDT........10W.
- Bibcode:1997IAUJD..14E..51G.
- S2CID 122929693.
- ^ P. Kunitzsch & T. Smart, Short Guide to Modern Star Names and Their Derivations (Wiesbaden: Otto Harrassowitz, 1986), p 49.
- ^ ISBN 978-0-486-21079-7.
- ^ "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
- ^ "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Archived (PDF) from the original on 2022-10-09. Retrieved 28 July 2016.
- ^ "IAU Catalog of Star Names". Retrieved 28 July 2016.
- ^ "Marcus Vitruvius Pollio: de Architectura, Book IX". Retrieved 8 October 2023.
- ^ (in Chinese) AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網2006年7月11日 Archived 2012-02-04 at the Wayback Machine
- ^ "Ian Ridpath's Star Tales – Perseus".
- ISBN 0-674-99479-5, IV.9, p.435.
- ^ Henry Cornelius Agrippa (1898). Three Books of Occult Philosophy. Lyons, 1531/33. Llewellyn reprint, 1993; tr. J. Freake (1651), ed. D. Tyson, p.411.
External links
- "Algol 3". SolStation. Retrieved 31 July 2006.
- "4C02517". ARICNS. 4 March 1998. Archived from the original on 10 February 2006. Retrieved 31 July 2006.
- "Algol". Alcyone ephemeris. Retrieved 8 June 2006.
- Bezza, Giuseppe. "Al-ghûl, the ogre". Translated by Daria Dudziak. Cielo e Terra. Archived from the original on 20 June 2006. Retrieved 8 June 2006.