编辑“︁聯星”︁（章节）

====食雙星====
{{main|食雙星}}
[[File:Eclipsing binary star animation 2.gif|thumb|一個[[食雙星]]，指示器的強度顯示光度的變化<ref>{{cite journal | first = D. | last = Gossman | title = Light Curves and Their Secrets | journal = Sky & Telescope | page = 410|date=October 1989}}</ref><ref>{{cite web | url = http://instruct1.cit.cornell.edu/courses/astro101/java/eclipse/eclipse.htm | title = Eclipsing Binary Simulation | publisher = Cornell Astronomy | deadurl = yes | archiveurl = https://web.archive.org/web/20080623203443/http://instruct1.cit.cornell.edu/courses/astro101/java/eclipse/eclipse.htm | archivedate = 2008-06-23 }}</ref>。]]

''食雙星''（或''食聯星''）是兩顆恆星的[[行星軌道|軌道]]平面幾乎躺在觀測者的視線方向上，因此天體會會發生[[食 (天文現象)|互食]]的現象。在這種情況下，這對也是光譜聯星的[[視差]]若也知道的話，對這對聯星的分析就很有價值<ref>{{cite web | url = http://www.physics.sfasu.edu/astro/ebstar/ebstar.html | first = D. | last = Bruton | title = Eclipsing Binary Stars | publisher = Stephen F. Austin State University | accessdate = 2008-04-28 | archive-date = 2016-06-12 | archive-url = https://web.archive.org/web/20160612194536/http://www.physics.sfasu.edu/astro/ebstar/ebstar.html | dead-url = no }}</ref>。[[大陵五]]是[[食雙星]]著名的例子<ref>{{cite web | url = http://www.physics.sfasu.edu/astro/ebstar/ebstar.html | title = Eclipsing Binary Stars | first = D | last = Bruton | publisher = Stephen F. Austin State University | accessdate = 2008-04-28 | archive-date = 2016-06-12 | archive-url = https://web.archive.org/web/20160612194536/http://www.physics.sfasu.edu/astro/ebstar/ebstar.html | dead-url = no }}</ref>。

在過去的十年裡，食聯星的基本參數已經可以使用8米等級的望遠鏡量測，這使得它們可以被當成[[標準燭光]]來使用。近年來，它們被用來直接測量和估計[[大麥哲倫星系]]（LMC）、[[小麥哲倫星系]]（SMC）、[[仙女座大星系]]和[[三角座星系]]的距離。以食聯星的方法直接測量，使星系距離的精確度誤差已經提高到5%以內的水準<ref name="Bonanos2006">
{{cite arxiv
| author=Bonanos, Alceste Z.
| title=Eclipsing Binaries: Tools for Calibrating the Extragalactic Distance Scale
| year=2006
| eprint=astro-ph/0610923
| class=astro-ph
}}</ref>。食聯星被歸類為[[變星]]，並不是因為它們個別成員的光度變化，而是因為[[變星#外因變星|外在因素造成的光度變化]]。食聯星的[[光度曲線]]特徵是原本穩定的光強度會週期性的下降一定的程度。如果其中的一顆恆星比較大，就有可能將另一顆完全遮蔽掉，而另一顆遮蔽它時就只能造成[[食 (天文現象)|環食]]的現象。

經由測量光度曲線的變化週期可以研究食聯星的[[行星軌道|軌道]]週期，而恆星相對的大小和軌道半徑可以根據光度變化的快慢和近星遮蔽遠星的強度來推算。如果它們還是光譜聯星，[[軌道要素]]也能夠測量出來，則恆星質量相對的也可以很容易得到。這意味著在這種情況下，恆星的相對密度也可以測出<ref>{{cite web | url = http://www.physics.sfasu.edu/markworth/ast105/Binary-Stars.ppt | format = [[Microsoft PowerPoint|PowerPoint]] | title = Binary Stars | first = M | last = Worth | publisher = Stephen F. Austin State University | accessdate = 2008-06-09 | archive-date = 2016-01-10 | archive-url = https://web.archive.org/web/20160110071759/http://www.physics.sfasu.edu/markworth/ast105/Binary-Stars.ppt | dead-url = no }}</ref>。