Binary systems in which both components can be seen are called visual binary stars :若雙星中所有成員皆可以看得到,我們便稱之為目視雙星。
Sometimes , in a binary star system , one star will pass in front of the other producing what we call eclipsing binary . it can be treated as a special kind of visual binary . eclipsing binary systems are variable stars see below :有些雙星系統(tǒng),其中一顆星會在另一顆星前經(jīng)過,產(chǎn)生周期性的光度變化,我們稱這種雙星為食雙星,基本上我們可以把食雙星看成為目視雙星的一種。