Multiple Stars

The only branch of Sidereal Astronomy which appears to admit of exact study is that of the relative motions of the Multiple Stars, first discovered by Herschell. By multiple stars astronomers understand stars very near each other, whose angular distance never exceeds a half minute, and which, for this reason, appear to be one, not only to the naked eye, but to ordinary telescopes, only the most powerful lenses being able to separate them. The relative movements of these stars tend to deceive us as to their precise multiple character, as, for instance, by mutual occultations, which do not permit us to separate them. Among some thousands of multiple stars registered in the catalogues, before the southern heavens had been really explored, almost all were only double, and we have found none which are more than triple,—a circumstance which may be owing solely to the imperfection of our telescopes, as we knew of none but single stars before Herschell's time. However interesting the study of them is, they constitute only a particular case in the universe, as the intervals of the stars which compose them are probably much smaller than those which divide the suns of the universe, so that the study of their relative motions does not lead us up to any of the great general phenomena of the heavens, and the speciality would be more conspicuous if astronomers did what I think they ought,—form their catalogues of those double stars only whose motions they have fully established.