Editing Eclipse (section)

==Eclipsing binaries==
A [[binary star]] system consists of two stars that orbit around their common [[centre of mass]]. The movements of both stars lie on a common [[orbital plane]] in space. When this plane is very closely aligned with the location of an observer, the stars can be seen to pass in front of each other. The result is a type of extrinsic [[variable star]] system called an [[eclipsing binary]].

The maximum [[luminosity]] of an eclipsing binary system is equal to the sum of the luminosity contributions from the individual stars. When one star passes in front of the other, the luminosity of the system is seen to decrease. The luminosity returns to normal once the two stars are no longer in alignment.<ref>{{cite web
 |last=Bruton 
 |first=Dan 
 |url=http://www.physics.sfasu.edu/astro/ebstar/ebstar.html 
 |title=Eclipsing binary stars 
 |publisher=Midnightkite Solutions 
 |access-date=2007-05-01 
 |url-status=dead 
 |archive-url=https://web.archive.org/web/20070414144827/http://www.physics.sfasu.edu/astro/ebstar/ebstar.html 
 |archive-date=2007-04-14 
}}</ref>

The first eclipsing binary star system to be discovered was [[Algol]], a star system in the constellation [[Perseus (constellation)|Perseus]]. Normally this star system has a [[visual magnitude]] of 2.1. However, every 2.867 days the magnitude decreases to 3.4 for more than nine hours. This is caused by the passage of the dimmer member of the pair in front of the brighter star.<ref>{{cite web 
|last=Price 
|first=Aaron 
|date=January 1999 
|url=http://www.aavso.org/vstar/vsots/0199.shtml 
|title=Variable Star Of The Month: Beta Persei (Algol) 
|publisher=AAVSO 
|access-date=2007-05-01 
|archive-url=https://web.archive.org/web/20070405003853/http://www.aavso.org/vstar/vsots/0199.shtml <!-- Bot retrieved archive --> |archive-date=2007-04-05 }}</ref> The concept that an eclipsing body caused these luminosity variations was introduced by [[John Goodricke]] in 1783.<ref>{{cite journal 
|last1=Goodricke 
|first1=John 
|author-link=John Goodricke 
|last2=Englefield 
|first2=H. C. 
|title=Observations of a New Variable Star 
|journal=Philosophical Transactions of the Royal Society of London 
|date=1785 
|volume=75 
|pages=153–164 
|bibcode=1785RSPT...75..153G 
|doi=10.1098/rstl.1785.0009 |s2cid=186208561 
|doi-access= 
}}</ref>