At its brightest, Algol is 3.3 times brighter than it is at its dimmest point. Its apparent visual magnitude changes over the range of 2.1 to 3.4 with a period of 2.87 days. Tidal distortions also result in “gravity darkening” effects, whereby in a significant number of images of Algol B, the edge or “limb” of the image is actually brighter than the center. Three fainter galaxies lie in the same field of view as Algol: the spiral galaxies IC 290 and IC 292, and the lenticular galaxy IC 294. [18][19] 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). 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. Algol is a known variable star, which waxes and wanes in brightness. The star spins considerably faster than the Sun, with a projected rotational velocity of 49 km/s. 2.23), the westernmost star of Orion’s Belt, Alphecca (Alpha Coronae Borealis, mag. It lies at an approximate distance of 90 light years from Earth and has an apparent magnitude … [Read more…]. Algol may have been the first variable star discovered. The flares take 20 to 50 hours to rise and have decay times of 10 to 40 days. Magnitudes are celestial numbers that measures how bright a sky object is; the smaller the value, the brighter the object. 2.09) in Orion and Kochab (Beta Ursae Minoris, mag. These cookies will be stored in your browser only with your consent. Luminosity: 10 solar luminosities Hipparchus (c. 190 – c. 120 BCE) and Pliny the Elder (23/24 – 79 CE) created a separate constellation of these stars and called it the Head of Medusa. of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090 (CC BY-SA 3.0). 3.80). "the Gorgon's head, a ghastly sight, The eclipsing binary pair is separated by only 0.062 astronomical units (AU) from each other, so close in fact that Algol A is slowly consuming the less massive Algol B by continually stripping off Algol B’s outer layers. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. The magnetic activity cycles of the subgiant and the mass transfer between the stars are believed to have an effect on the recurrent variations in the orbital period. Like many other bright stars, Algol has often been used in the works of fiction, as well as in films, television, and games. The Washington Double Star Catalog lists two other companions, designated Beta Persei B and C, about one arcminute away. Rotational velocity: 49 km/s Age: 570 million years, Spectral class:  K0IV Similarly, watch during the two hours following minimum for a distinct upturn in brightness. The WGSN's first bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included Algol for this star. Vogel is credited for inventing the photographic-spectroscopic radial velocity measurements of stars and, in his work, he discovered that spectra of some stars shifted slightly toward the red and then toward the blue, indicating that the stars were moving toward and away from the Earth. It is a perfect example of an "eclipsing binary" star, which brightens and dims almost as regular as clockwork. [42] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[43] to catalog and standardize proper names for stars. The Greeks associated the star with the Gorgon Medusa, a mythical creature with hair made of snakes and a face so horrifying that it turned those who looked at it to stone. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York. 3.39), Miram (Eta Per, mag. Gallery: Amazing Skywatcher Photos from Around the World, 10 Most Popular Skywatching Misconceptions Explained, Best Telescopes for Beginners | Telescope Reviews & Buying Guide, Amazing Astronomy: Victorian-Era Illustrations of the Heavens. Absolute magnitude: – 0.07 Absolute magnitude: 2.9 Some difficulties in explaining the observed spectroscopic features led to the conjecture that a third star may be present in the system; four decades later this conjecture was found to be correct.[24]. These two stars can be found using the two prominent northern asterisms: the Great Square of Pegasus and Cassiopeia’s W. Andromeda’s brightest stars – Alpheratz, Mirach and Almach – form a chain that connects the constellations Pegasus and Perseus. Temperature: 13,000 K This table shows the predicted times of minimum brightness for the "Demon Star" Algol. [49], Coordinates: 03h 08m 10.1315s, +40° 57′ 20.332″, This article is about the star. All rights reserved. The star has been known since ancient times. Beta Persei Ab has 1.76 solar masses and a radius 1.73 times that of the Sun. The star is also known as Gorgona, Gorgonea Prima, Demon Star and El Ghoul. [16], The variability of Algol was noted in 1667 by Italian astronomer Geminiano Montanari,[17] 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. ©2020 Verizon Media. 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. The star that was originally more massive – now a class K subgiant – has filled its Roche lobe and transferred much of its mass onto the companion, all the while evolving and reaching the next stage faster. [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. Beta Lyrae variables are binary stars that are so close together that their shapes are distorted into ellipsoidal and there is extensive mass flow in the systems, while W Ursae Majoris variables are contact binary systems that have a common envelope of material and transfer mass through a connecting neck. Anthony Shepherd, Plumian Professor of Astronomy and Experimental Philosophy at Cambridge, Goodricke wrote: If it were not perhaps too early to hazard even a conjecture on the cause of this variation, I should imagine it could hardly be accounted for otherwise than either by the interposition of a large body revolving around Algol, or some kind of motion of its own, whereby part of its body, covered with spots or such like matter, is periodically turned towards the earth. This animation was assembled from 55 images of the CHARA interferometer in the near-infrared H-band, sorted according to orbital phase. of Astronomy, University of Michigan, Ann Arbor, MI 48109-1090. Corrections? A Latin name for Algol from the 16th century was Caput Larvae or "the Spectre's Head". The star, known as Algol, is located in the constellation of Perseus, the Hero, and has been known since ancient times as "The Demon Star.". 10.8), the spiral galaxy NGC 1003 (mag. The constellation is also home to a number of notable deep sky objects. Algol, Beta Persei, is a bright multiple star located in Perseus. In a binary star system, components form at about the same time. With an apparent magnitude of 2.12, Algol is the second brightest star in Perseus, after Mirfak. He found that the companion gave off more light than the Sun and was much brighter on the side facing the primary component. Phases sorted by Stigmatella Aurantiaca. The star’s Hebrew name was Rōsh ha Sāṭān, “the head of Satan.” The star was also associated with Lilith, Adam’s first wife. Updates? If it were exactly, or more nearly, in our line of sight, we would have a total eclipse of Star A by Star B and the effect would be even more apparent, but even so, the variable brightening and dimming is still a fascinating sight to see. Algol came within 9.8 light years of the Sun 7.3 million years ago. [28], Studies of Algol led to the Algol paradox in the theory of stellar evolution: although components of a binary star form at the same time, and massive stars evolve much faster than the less massive stars, the more massive component Algol Aa1 is still in the main sequence, but the less massive Algol Aa2 is a subgiant star at a later evolutionary stage. Agrippa wrote, “Under the Head of Algol, they made an image whose figure was the head of a man with a bloody neck; they report that it bestoweth good success to petitions, and make him go carrieth it bold and magnanimous, and preserveth the members of the body sound; also it helpeth against witchcraft, and reflecteth evil endeavours, and wicked incantations upon our adversaries.”, The name Algol (pronunciation: /ˈælɡɒl/) comes from the Arabic phrase raʾs al-ghūl, meaning “the head of the ogre.” Al Ghul originally meant “mischief-maker.”.