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The Algol star system was known at least since antiquity. The [[Ancient Greeks]] called Algol the "Evil eye" of [[Medusa]].  This was most likely due to the regular occurrences of the change in brightness and color as Beta Persei B eclipsed Beta Persei A. The name Algol itself is derived from the [[Arabic]] term أس الغول ''ra's al-ghūl'', meaning the Demon's Head or the Head of the Ogre. The name likely stems from the [[Greek]] view of the star system, specifically [[Ptolemy]], who named it as ''τῶν ἐν γοργονίῳº ὁ λαμπρός'', meaning "the bright one of those in the [[Gorgon|Gorgon's]] head". The names "Blinking Demon" and "Demon Star" are [[English]] translations of the Arabic name.<ref>Allen, Richard Hinckley (1963). Star Names: Their Lore and Meaning (revised edition). Dover. pp. 332–33. ISBN 0-486-21079-0. OCLC 185804232 637940</ref>

The Algol star system was known at least since antiquity. The [[Ancient Greeks]] called Algol the "Evil eye" of [[Medusa]].  This was most likely due to the regular occurrences of the change in brightness and color as Beta Persei B eclipsed Beta Persei A. The name Algol itself is derived from the [[Arabic]] term أس الغول ''ra's al-ghūl'', meaning the Demon's Head or the Head of the Ogre. The name likely stems from the [[Greek]] view of the star system, specifically [[Ptolemy]], who named it as ''τῶν ἐν γοργονίῳº ὁ λαμπρός'', meaning "the bright one of those in the [[Gorgon|Gorgon's]] head". The names "Blinking Demon" and "Demon Star" are [[English]] translations of the Arabic name.<ref>Allen, Richard Hinckley (1963). Star Names: Their Lore and Meaning (revised edition). Dover. pp. 332–33. ISBN 0-486-21079-0. OCLC 185804232 637940</ref>

In [[Hebrew]] legend, the star was seen as ''Rōsh ha Sāṭān'' or '[[Satan|Satan's]] head'. It was also linked with the mythical [[Lilith]]. In Latin it was called ''Caput Larvae'', or 'Spectre's Head'.<ref name="penelope">http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Perseus*.html</ref> [[Medieval]] [[Europe|Europeans]] saw Algol as one of the 15 Behenian stars used for [[astrology]].<ref>Tyson, Donald; Freake, James (1993). Three Books of Occult Philosophy. Llewellyn Worldwide. ISBN 0875428320. OCLC 26634250 41597186</ref> The [[Chinese]] named the star 大陵五, meaning the Fifth Star of the Mausoleum, although they also named it 叠尸 or ''Tseih She'', meaning 'Piled up corpses'.<ref name="penelope">http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Perseus*.html</ref>

In [[Hebrew]] legend, the star was seen as ''Rōsh ha Sāṭān'' or '[[Satan|Satan's]] head'. It was also linked with the mythical [[Lilith]]. In Latin it was called ''Caput Larvae'', or 'Spectre's Head'.<ref name="penelope">http://penelope.uchicago.edu/Thayer/E/Gazetteer/Topics/astronomy/_Texts/secondary/ALLSTA/Perseus*.html</ref> [[Medieval]] [[Europe]]ans saw Algol as one of the 15 Behenian stars used for [[astrology]].<ref>Tyson, Donald; Freake, James (1993). Three Books of Occult Philosophy. Llewellyn Worldwide. ISBN 0875428320. OCLC 26634250 41597186</ref> The [[Chinese]] named the star 大陵五, meaning the Fifth Star of the Mausoleum, although they also named it 叠尸 or ''Tseih She'', meaning 'Piled up corpses'.<ref name="penelope"/>

The first known recording of Algol's regular variation in its magnitude was in 1667 by Geminiano Montanari. In May 1783, John Goodricke presented his findings on the proposed cause of Algol's variability to the Royal Society. He believed a dark body regularly passed in front of the star, or that the star itself had some dark spot.<ref>http://www.surveyor.in-berlin.de/himmel/Bios/Goodricke-e.html</ref> It wasn't until 1881, that Edward Pickering, an astronomer from [[Harvard]], brought forth evidence that Algol was an eclipsing binary star system.<ref>http://adsabs.harvard.edu/abs/1881AReg...19..253.</ref> This was confirmed in 1889 by Hermann Carl Vogel, who discovered periodic [[Dopper Shift|Doppler shifts]] in the spectrum of Algol A and the eclipsing Algol B.<ref>http://adsabs.harvard.edu/abs/1989SSRv...50....1B</ref>

The first known recording of Algol's regular variation in its magnitude was in 1667 by Geminiano Montanari. In May 1783, John Goodricke presented his findings on the proposed cause of Algol's variability to the Royal Society. He believed a dark body regularly passed in front of the star, or that the star itself had some dark spot.<ref>http://www.surveyor.in-berlin.de/himmel/Bios/Goodricke-e.html</ref> It wasn't until 1881, that Edward Pickering, an astronomer from [[Harvard]], brought forth evidence that Algol was an eclipsing binary star system.<ref>http://adsabs.harvard.edu/abs/1881AReg...19..253.</ref> This was confirmed in 1889 by Hermann Carl Vogel, who discovered periodic [[Dopper Shift|Doppler shifts]] in the spectrum of Algol A and the eclipsing Algol B.<ref>http://adsabs.harvard.edu/abs/1989SSRv...50....1B</ref>

==Star System==

==Star System==

Algol is a triple star system. The first two [[star|stars]] make up the famous eclipsing binary and are separated from each other by a distance of only 0.062 AU. The orbit of the two stars is highly circular and take only 2.87 days to complete. From [[Earth]], the orbit is inclined at 97.69°.<ref>http://adsabs.harvard.edu/abs/1996AAS...188.6014M</ref> A third star orbits the first two at the distance of 2.69 AU, taking some 1.86 years to complete with an inclination of 83.98°.<ref>http://ad.usno.navy.mil/wds/orb6.html</ref>

Algol is a triple star system. The first two [[star]]s make up the famous eclipsing binary and are separated from each other by a distance of only 0.062 AU. The orbit of the two stars is highly circular and take only 2.87 days to complete. From [[Earth]], the orbit is inclined at 97.69°.<ref>http://adsabs.harvard.edu/abs/1996AAS...188.6014M</ref> A third star orbits the first two at the distance of 2.69 AU, taking some 1.86 years to complete with an inclination of 83.98°.<ref>http://ad.usno.navy.mil/wds/orb6.html</ref>

===Beta Persei A===

===Beta Persei A===

'''Algol A''' (Beta Persei A) is a blue white main sequence dwarf star of spectral type B5-8 V, and the most massive of the triple star system. The star has a diameter 2.88 times that of our [[Sun]] with a mass 3.59 times as great.<ref name="kim">http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1989ApJ...342.1061K</ref> The star is considerably brighter than the Sun. Its visual luminosity is 98 times of the Sun, and the total luminosity though is some 200 times as great, accounting for [[ultraviolet]] [[radiation]]. Algol A rotates at a quick 65 km/sec and could possibly be less then 300 million years old.

'''Algol A''' (Beta Persei A) is a blue white main sequence dwarf star of spectral type B5-8 V, and the most massive of the triple star system. The star has a diameter 2.88 times that of our [[Sun]] with a mass 3.59 times as great.<ref name="kim">http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1989ApJ...342.1061K</ref> The star is considerably brighter than the Sun. Its visual luminosity is 98 times of the Sun, and the total luminosity though is some 200 times as great, accounting for [[ultraviolet]] [[radiation]]. Algol A rotates at a quick 65&nbsp;km/sec and could possibly be less than 300 million years old.

===Beta Persei B===

===Beta Persei B===

'''Algol B''' (Beta Persei B) is a orange-red subgiant star of spectral class K0-2 IV. Once the most massive of the three stars of the system, it has become a cool, low-mass star that has distorted into a teardrop shape from the [[tidal force|tidal forces]] caused by its companion, Algol A. The gas from Algol B itself is being drained slowly away in an accretion stream towards its close companion, now the more massive of the two stars. Algol B itself has around 79 percent of our Sun's mass and 3.54 times its diameter. As a subgiant, the star is also 3.4 times as luminous as our Sun.<ref name="kim">http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1989ApJ...342.1061K</ref>

'''Algol B''' (Beta Persei B) is an orange-red subgiant star of spectral class K0-2 IV. Once the most massive of the three stars of the system, it has become a cool, low-mass star that has distorted into a teardrop shape from the [[tidal force]]s caused by its companion, Algol A. The gas from Algol B itself is being drained slowly away in an accretion stream towards its close companion, now the more massive of the two stars. Algol B itself has around 79 percent of our Sun's mass and 3.54 times its diameter. As a subgiant, the star is also 3.4 times as luminous as our Sun.<ref name="kim"/>

===Beta Persei C===

===Beta Persei C===

'''Algol C''' (Beta Persei C) is a blue white main sequence dwarf of spectral type A5 V. The star has 1.7 times our Sun's diameter and 1.67 times its mass. Its luminosity is around 4.1 times that of our Sun. Algol C orbits the other two stars with an average orbit of 2.69 AU.<ref name="kim">http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1989ApJ...342.1061K</ref>

'''Algol C''' (Beta Persei C) is a blue white main sequence dwarf of spectral type A5 V. The star has 1.7 times our Sun's diameter and 1.67 times its mass. Its luminosity is around 4.1 times that of our Sun. Algol C orbits the other two stars with an average orbit of 2.69 AU.<ref name="kim"/>

For an [[terrestrial planet|Earth-like]] world to have liquid [[water]] on its surface, it would have to be around 14 AU from the three stars, or the equivalent of an orbit between [[Saturn]] and [[Uranus]]. The hypothetical world would have an orbital period of over 27 years. Because the system itself is very young, it is unlikely such a planet would have time to cool to the point of holding water.

For an [[terrestrial planet|Earth-like]] world to have liquid [[water]] on its surface, it would have to be around 14 AU from the three stars, or the equivalent of an orbit between [[Saturn]] and [[Uranus]]. The hypothetical world would have an orbital period of over 27 years. Because the system itself is very young, it is unlikely such a planet would have time to cool to the point of holding water.