What is Algol?
[[Image:Position Beta Per.png|right|thumb|250px|This is '''Algol''' in the sky]] [[File:Algol AB movie imaged with the CHARA interferometer.gif|thumb|right|200px|English: Algol (β Persei) is a triple-star system (Algol A, B, and C) in the constellation Perseus. The large and bright primary Algol A is regularly [[eclips]]ed by the dimmer Algol B every 2.87 days. The pair is separated by only 0.062 [[astronomical unit]]s (AU) from each other, so close that Algol A is slowly stripping off Algol B's outer layers.]] '''Algol''', also known as the '''Demon Star''', is a bright [[star]] in the [[Perseus (constellation)|Perseus]] [[constellation]]. It is one of the best known double stars that can only be seen in [[spectroscope]]s, the first star of its type discovered, and one of the first [[variable star]]s to be discovered before it explodes. Algol is made of three stars (Beta Persei A, B and C) and the brightest is '''Persei A'''. These stars partly [[eclipse]] each other every 2&nbsp;days, 20&nbsp;hours and 49&nbsp;minutes for 10 hours.<ref>Beta Persei, American Association of Variable Star Observers. http://www.aavso.org/vstar/vsots/0199.shtml {{Webarchive|url=https://web.archive.org/web/20060708092301/http://www.aavso.org/vstar/vsots/0199.shtml |date=2006-07-08 }}</ref> ==References== {{reflist}} [[Category:Variable stars]] [[Category:Binary stars]]