Temperature: 4,500 K, Spectral class:  A7m Radius: 1.73 solar radii 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. When we look at the stars in the sky, a few have distinctive colours to the naked eye, like Rigel and Betelgeuse in Orion, but most of them appear just white. The bright stars of Cassiopeia can be used to star-hop to Mirfak, the brightest star in Perseus and the central star of the Alpha Persei Cluster, and then to Algol. Algol The primary to the Algolian homeworld, a B-class star, is also known as Beta Persei in the old Terran Bayer classification system. Perseus and Caput Medusæ, plate 6 in Urania’s Mirror, a set of celestial cards accompanied by A familiar treatise on astronomy … by Jehoshaphat Aspin. Arthur: Star of Bootes, situated in the extension of the tail of Ursa Major. Algol – the “demon” star The shape and timing of the eclipses gives the shape and size of the stars. Mirfak lies along the imaginary line extended from Gamma to Delta Cassiopeiae, and forms a triangle with Algol and the bright Almach, Gamma Andromedae. Declination: +40°57’20.3280’’ Absolute magnitude: 2.3 Two nearby stars, Epsilon Persei (mag. Temperature: 7,500 K. In 2003, the General Catalogue of Variable Stars listed more than 3,500, which was 9% of all known variables. Right ascension: 03h 08m 10.13245s 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. 2.00), the second brightest star in Vela and one of the stars of the False Cross, and Almaaz (Epsilon Aurigae, mag. Constellation: Perseus Algol’s brightness is usually at magnitude 2.1, with 10-hour long eclipses occurring every 2.867328 days (2 days, 20 hours and 49 minutes), when the fainter Beta Persei Aa2 passes in front of Beta Persei Aa1 and the system’s magnitude drops to 3.4. The paradox is explained with mass transfer, a phenomenon that is not uncommon in close binary stars. Rotational velocity: 49 km/s Beta Lyrae and W Ursae Majoris variables, is that Algol-type stars have a spherical or slightly ellipsoidal shape. Mass: 1.76 solar masses It is the brightest of a quartet of stars called Gorgonea. Luminosity: 10 solar luminosities The studies of Algol challenged the theory that stars’ rate of evolution depends on their mass, meaning that, the greater the mass, the sooner the star will evolve off the main sequence. It revolves around the main binary pair every 1.85 years. Interpolation of the orbit of Aa2 around Aa1 with focus on Aa1.Photos taken with the CHARA interferometer in the near-infrared H-band. Their components are not so close together as to cause deformations in shape, which is the case with the other two types. In 2003, the General Catalogue of Variable Stars listed more than 3,500, which was 9% of all known variables. This star represents the head of mythological monster, Medusa. This is because our eyes, especially in low light conditions, cannot distinguish colour very well. This is not an artistic representation, but rather is a true two-dimensional image with 1/2 milli-arcsecond resolution in the near-infrared H-band, reconstructed from data of the CHARA interferometer. 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). Age: 570 million years, Spectral class:  K0IV Algol, Beta Persei, is a bright multiple star located in Perseus. Star - Star - Eclipsing binaries: An eclipsing binary consists of two close stars moving in an orbit so placed in space in relation to Earth that the light of one can at times be hidden behind the other. You will also be asked to do a paper review of a journal article on some variable star classification or light curve related subject. that it is periodically eclipsed by a dimmer companion of almost the same size as itself. ALGOL: Star b of the constellation of Perseus. Copy this URL to share: 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. Constellation Home. Because some phases are poorly covered, B jumps at some points along its path. Algol is a known variable star, which waxes and wanes in brightness. No. 2.88) and Almach (mag 2.1) can be used for reference when watching the progress of the eclipses. The star is also known as Gorgona, Gorgonea Prima, Demon Star and El Ghoul. Today, Algol is the 61st brightest star in the sky at its brightest (mag. Even though both components in the binary system formed at approximately the same time, the primary, more massive star in the system is still on the main sequence, while the less massive secondary component has evolved into a subgiant. After observing the star to determine the period of its light variations, he suggested that Algol was what we now know as an eclipsing binary, i.e. As our understanding grows (and new types of objects are discovered), the classification criteria change. As they orbit each other, the stars pass in front of each other, causing eclipses. A third component, much fainter than the other two stars, was also detected in the system. The Roche lobe represents the maximum a star can reach before it starts transferring material to the companion. The Algol system as it appeared on 12 August 2009. Tidal distortions of Algol B giving it an elongated appearance are readily apparent. Algol, Epsilon Persei and Almach, image: Wikisky. Algol’s variability was first correctly explained by the English amateur astronomer John Goodricke in 1782, when he was only 18 years of age. 466. 2.11) in Leo, Saiph (Kappa Orionis, mag. that it is p… Radius: 3.48 solar radii After observing the star to determine the period of its light variations, he suggested that Algol was what we now know as an eclipsing binary, i.e. 2.21) in Carina, and Suhail (Lambda Velorum, mag. The separation has to be pretty small for the odds to be good this will happen. Algol, Beta Persei (β Per) is a triple star system located in the constellation Perseus. 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. Absolute magnitude: 2.9 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. 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. Luminosity: 182 solar luminosities Algol currently lies at a distance of about 90 light years, but it was once much closer to the solar system. The star’s brightness can sometimes be seen falling and rising on the same night. of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090. The star has been known since ancient times. Goodricke also discovered the periodic variation of Delta Cephei, the prototype for the Cepheid variable stars. Image: Dr Fabien Baron, Dept. The phase of each image is indicated at the lower left. 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. 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. Algol was one of the first non-nova variable stars ever discovered. (Sirius has an apparent magnitude of -1.46.) Algol is one of the best known variable stars in the sky and a prototype for a class of eclipsing variable stars known as Algol variables. 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. 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). Algol and β Lyrae eclipsing binaries are differentiated by constant variation in the light curve outside of eclipses for the β Lyrae systems to the nearly constant brightness outside of eclipses of the Algol-type systems. 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. 2.08) in Ursa Minor, and it just outshines Muhlifain (Gamma Centauri, mag. star classification in a critical or unconventional manner. This does not appear to be happening with Algol. About 7.3 million years ago, it came within 9.8 light years of the Sun and shone at magnitude of about -2.5, which is much brighter than Sirius is today. Commonly known as the Demon Star, it is one of the best-known variable stars in the sky and a prototype for a class of eclipsing variable stars known as Algol variables. Refer to Hoffman et al. Algol with Pi, Rho and Omega Persei, image: Wikisky. It is only slightly fainter than Denebola (Beta Leonis, mag. If we could, we would see that stars vary a great deal in the wavelengths of the light they produce. Algol’s eclipses can be observed without a telescope. The form of Algol C, however, is an artifact. 2.09) in Orion and Kochab (Beta Ursae Minoris, mag. 2.12). star if the period, inclination, and radial velocity of each star is known. Algol is the best known variable star of its type, but there are countless other Algol variables known. The elongated appearance of Algol B and the round appearance of Algol A are real. One of the 15 Behenian stars, was also detected in the northern constellation Auriga some variable of! 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