Algol was one of the first non-nova variable stars ever discovered. Distance: 90 light years (28 parsecs) Observations of Algol led to the Algol paradox, which lay in the disparity between the mass and evolutionary stage of the two components of the eclipsing binary system. that it is periodically eclipsed by a dimmer companion of almost the same size as itself. The more evolved secondary component was not always the less massive one, but the flow of material between the stars disturbed the normal evolution process and the originally more massive star (in this case the subgiant) lost much of its mass to the companion (the main sequence star). Absolute magnitude: 2.9 The star has been associated with demons, violence and death across different cultures: ghouls in the Arabic world, the Gorgon in Greek mythology, and Rōsh ha Sāṭān (Satan’s Head) in Hebrew folklore. Algol is a known variable star, which waxes and wanes in brightness. The Roche lobe represents the maximum a star can reach before it starts transferring material to the companion. Algol with Pi, Rho and Omega Persei, image: Wikisky. Algol, Epsilon Persei and Almach, image: Wikisky. The star’s brightness can sometimes be seen falling and rising on the same night. It lies at an approximate distance of 90 light years from Earth and has an apparent magnitude that varies between 2.12 and 3.4. 2.23), the brightest star in Corona Borealis, Alsephina (Delta Velorum, mag. 2.98), one of the brightest stars in the northern constellation Auriga. It is a triple star system composed of Beta Persei Aa1, a B-class main sequence star, Beta Persei Aa2, an orange subgiant, and Beta Persei Ab, a dimmer A-class star. The other three stars, all located in the vicinity of Algol, are Pi Persei (π Persei, Gorgonea Secunda), a white main sequence star with an apparent magnitude of 4.7, Rho Persei (ρ Persei, Gorgonea Tertia), a reddish (class M) bright giant with a visual magnitude of 3.39, and Omega Persei (ω Persei, Gorgonea Quarta), an orange giant with a magnitude of 4.6. A third component, much fainter than the other two stars, was also detected in the system. The images vary in quality, but the best have a resolution of 0.5 milliarcseconds, or approximately 200 times better than the Hubble Space Telescope. The oldest written record of its discovery – an Ancient Egyptian Calendar of Lucky and Unlucky Days – is about 3,200 years old. This star represents the head of mythological monster, Medusa. of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090. Declination: +40°57’20.3280’’ What distinguishes Algol variables from, e.g. Mirfak lies along the imaginary line extended from Gamma to Delta Cassiopeiae, and forms a triangle with Algol and the bright Almach, Gamma Andromedae. The elongated appearance of Algol B and the round appearance of Algol A are real. Algol /ˈælɡɒl/, 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. 2.21) in Carina, and Suhail (Lambda Velorum, mag. Absolute magnitude: – 0.07 As they orbit each other, the stars pass in front of each other, causing eclipses. Other famous deep sky objects in this region include the California Nebula (NGC 1499) and the Heart and Soul nebulae (IC 1805 and IC 1848). Temperature: 13,000 K Beta Lyrae and W Ursae Majoris variables, is that Algol-type stars have a spherical or slightly ellipsoidal shape. Algol (β Persei) is a triple-star system (Algol A, B, and C) in the constellation Perseus, in which the large and bright primary Algol A is regularly eclipsed by the dimmer Algol B every 2.87 days. 2.08) in Ursa Minor, and it just outshines Muhlifain (Gamma Centauri, mag. Two nearby stars, Epsilon Persei (mag. As our understanding grows (and new types of objects are discovered), the classification criteria change. Since you also know the velocity (from Doppler shift) and orbital period, you can get the true scale of the system (including star sizes and masses). Initially, the star system seemed to evolve in a manner that defied established beliefs about stellar evolution. Mass: 3.17 solar masses There are many variable stars known throughout the heavens, but Algol might well be the most famous variable star … In 2003, the General Catalogue of Variable Stars listed more than 3,500, which was 9% of all known variables. Temperature: 4,500 K, Spectral class: A7m The star’s Latin name in the 16th century was Caput Larvae, meaning “the Spectre’s Head.” Medieval astrologers considered Algol one of the unluckiest stars. You know the system is nearly edge on. It is the brightest of a quartet of stars called Gorgonea. Almach is the third star in the chain that leads from Alpheratz and the Great Square of Pegasus to Perseus. Visible Algol-type variable stars include Mintaka (Delta Orionis, mag. 2.00), the second brightest star in Vela and one of the stars of the False Cross, and Almaaz (Epsilon Aurigae, mag. Image: Dr Fabien Baron, Dept. 2.11) in Leo, Saiph (Kappa Orionis, mag. Constellation Home. Algol is relatively easy to find because it is located in the same area of the sky as Cassiopeia and the Great Square of Pegasus, between Cassiopeia’s W and the Pleiades. It revolves around the main binary pair every 1.85 years. that it is p… 2.23), the westernmost star of Orion’s Belt, Alphecca (Alpha Coronae Borealis, mag. Luminosity: 182 solar luminosities Interpolation of the orbit of Aa2 around Aa1 with focus on Aa1.Photos taken with the CHARA interferometer in the near-infrared H-band. Algol’s eclipses can be observed without a telescope. Over time, the more massive and evolved star sheds much of its material, which is accreted by the companion, which then gradually becomes more massive. The name Algol comes from the Arabic phrase “raʾs al-ghūl,” meaning the “head of the ghoul” or “head of the demon.” In Perseus, the star represents the head of the Gorgon Medusa, the mythical monster so horrific in appearance that merely looking at her would turn people to stone. London. Algol is the best known variable star of its type, but there are countless other Algol variables known. 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