William Herschel : Tofauti kati ya masahihisho

Aliangalia pia [[nyota pacha|nyota maradufu]] akitoa ufafanuzi wa kwanza kwa kuwepo kwao<ref>Herschel, W. (1802) uk.481: "If .. two stars should really be situated very near each other, and at the same time so far insulated as not to be materially affected by the attractions of neighbouring stars, they will then compose a separate system, and remain united by the bond of their own mutual gravitation towards each other. This should be called a real double star; and any two stars that are thus mutually connected, form the binary sidereal system which we are now to consider."</ref>.